Tri mix instructor guide

DSAT Tec Trimix Diver CourseInstructor Guide

Section ONE: DSAT Tec Trimix Diver Instructor Guide

DSAT Tec Trimix Diver Instructor Guide© International PADI, Inc. 2003

Produced by Diving Science and Technology Corp. (DSAT)

for International PADI, Inc.

All rights reserved

Portions of the Appendix of this section may be reproducted by PADI Members

for use in PADI-sanctioned training, but not for resale or personal gain. No other

reproduction is allowed without the express written permission of the publisher.

Published and distributed by

PADI

30151 Tomas Street

Rancho Santa Margarita, CA 92688

Printed in the U.S.A.

Product No. 70430 Version 1.0 (includes Binder) (06/03)

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Instructor Guide Section ONE: DSAT TecTrimix Diver

Table of ContentsSection ONE: Introduction

Intructional Philosophies and Course Goals 1-1

DSAT Tec Trimix Diver Course Goals 1-4

Course Overview 1-5

Knowledge Development 1-5

Training Dives 1-5

Section TWO: Course Standards

Legal and Regulatory Considerations 2-1

Instructor Requirements 2-2

Requirements to Qualify Through a DSAT Tec Trimix Instructor 2-2

Training Course

Requirements to Quality by Applying Directly to PADI 2-3

Certified Assistant Requirements 2-4

Course Prerequisites 2-5

Equipment Requirements 2-5

Instructor Materials 2-7

Student Materials 2-7

Paperwork and Administration 2-8

Insurance Requirements 2-8

Certification Procedures 2-9

Course Sequence and Preassessment Requirements 2-9

Knopwledge Development Preassessments 2-10

Training Dive Standards 2-11

Confined and Limited Open Water 2-11

Open Water Training Standards 2-12

Water Skills Assessment 2-13

Definitions of Mastery 2-13

Optional Dives for Tec Deep Divers 2-14

Cave Environment Training Option 2-14

Instructor Requirements 2-14

Certified Assistant Requirements 2-15

Student Requirements 2-15

Environment Requirements 2-15

Equipment and Gas Requirements 2-15

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Section THREE: Course Outline

I. Course Sequence 3-1

II. Use of Outline and Materials 3-2

III. Knowledge Development Presentation One 3-4

IV. Practical Application One 3-26

V. Assessment Dive 3-29

VI. Training Dive One 3-35

VII. Knowledge Development Presentation Two 3-42

VIII. Practical Application Two 3-66

IX. Training Dive Two 3-68

X. Knowledge Development Presentation Three 3-74

XI. Practical Application Three 3-80

XII. Training Dive Three 3-82

XIII. Training Dive Four 3-87

XIV. Knowledge Development Presentation Four 3-93

XV. Practical Application Four 3-97

XVI. Training Dive Five 3-99

XVII. Training Dive Six 3-105

XVIII. Practical Application Five 3-109

XIX. Training Dive Seven 3-110

XX. Training Dive Eight 3-113

AppexdixAppendix Table of Contents A-1

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This symbol signifies notes addressed

to you the instructor


DSAT Tec Trimix Diver CourseInstructor Guide

ONE: IntroductionInstructional Philosophies and Course GoalsThe DSAT Tec Trimix Diver course is intended to

extend the depth range available to technical

divers trained and qualified to use air, enriched

air and oxygen for technical decompression dives

beyond 50 metres/165 feet in open water. As part

of the DSAT TecRec instructional umbrella, the

Tec Trimix Diver course reflects the training

philosophies exhibited by the prerequisite Tec

Deep Diver and Apprentice Tec Diver courses.

The approach is an instructional progression that

directly addresses the added hazards, greater

demands and challenges present in technical div-

ing, most of which become more pronounced in

the depth ranges typically associated with trimix

use.

DSAT TecRec courses consider two primary

philosophies in training technical divers:

• Technical diving is not for everyone. It should not be presented as a

goal for all divers to aspire to. Rather, DSAT TecRec courses are for the

small segment of divers looking for greater challenge and willing to

accept the costs, risks, training and physical fitness requirements neces-

sary. It may be perfectly appropriate to remind those who may not be

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suited to a particular TecRec course, or technical diving in general, that

they can enjoy a lifetime of novel diving adventures without ever leaving

recreational limits.

• No instructor is required to accept a particular individual into a scuba

course (provided the basis for not accepting someone does not violate

national or local discrimination laws involving race, gender, etc.). In

deciding whether it’s appropriate to accept someone into a technical div-

ing course, or to have someone continue in a course, the following points

are worth considering:

1. What comfort level does the individual demonstrate underwater?

Technical diving imposes task loading and higher potential risk, partic-

ularly in deep diving when gas supply and decompression may create

significant time pressure. Problems have a higher probability of being

more substantial than within the recreational diving envelope. A tech-

nical diving student needs to be able to control emotions and put

aside anxiety in the face of problems

and task loading. An individual who

exhibits undue stress during exercises,

a tendency to overreact, or inappropri-

ate emotional reactions may not be

ready for the psychological stresses of

technical diving. The clues might

include an inability to perform simple

tasks that they handled easily under

“relaxed” circumstances; unnecessarily

hasty or forceful responses to simple

problems; irritability or anger in the

face of minor obstacles, etc.

2. What skill level does the individual

demonstrate? Recreational diving princi-

ples, procedures and motor skills need

to be second nature before going into

technical diving. Previously-learned

technical diving skills need to be second

nature before going into trimix diving.

An individual who’s still mastering these points is not ready for higher

skill demands.

3. Do your observations match the certification level? Just because a stu-

dent has met prerequisite certification requirements doesn’t guarantee

the student’s ready for the next level. Individuals who have not applied

those skills for some time may not be at their prior level any longer.

Individuals coming from outside of the DSAT TecRec structure may

come from instructional systems that are less rigorous with respect to

performance.

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4. What is the individual’s physical fitness? Compared to recreational

diving, the physical demands of technical diving can be much higher,

especially before and after the dive, and during the dive in current or

any other situation requiring above normal exertion while swimming.

This means more load on the legs and cardiovascular system. There’s

substantially more equipment, translating to higher effort necessary to

move the mass and increased drag. Technical dive duration frequently

requires heavy exposure protection;

laden with tec gear and a full exposure

suit in a hot climate predive can risk

overheating and significant cardiovascu-

lar stress. For all these reasons, the

DSAT Tec Trimix Diver course requires

a physician’s approval prior to any

inwater training. See Section Two:

Course Standards for details on medical

screen requirements.

The greater the potential risk, the more important it is

to apply accepted instructional methodologies, educa-

tional and cognitive psychology and system teaching

principles in course design. DSAT TecRec courses,

including the Tec Trimix Diver course, depart signifi-

cantly in several ways compared to tec diver courses

not founded on performance-based, valid instructional

system design.

• Technical diving calls for a high level of knowledge development, motor

skill automaticity (the ability to do something without stopping to think

about it) and self confidence. To accomplish these, TecRec programs

emphasize in-depth, comprehensive knowledge development and extensive

application, practice and simulation underwater.

• DSAT TecRec programs emphasize training in the way you actually dive. In

accord with instructional system design philosophy, the courses exclude

anything that has no real application in tec diving. Including them would

simply interfere with learning.

• Technical diving has extensive equipment requirements. TecRec courses

approach their subject matter with the assumption that students have

their own equipment and/or are prepared to invest in it. This is particularly

true at the Tec Trimix level. (This does not eliminate rental options as

appropriate, though students should become familiar with the gear prior to

tec diving with it.)

• Because DSAT TecRec courses apply instructional system design from the

ground up to achieve specific training goals, the TecRec system does not

necessarily have the same certification levels as other tec training organi-

zations. Valid course design assigns breaks between courses based on

applicable groups of learned capabilities. This avoids certification levels

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with arbitrary divisions and little meaningful difference in training. This

also eliminates the situation in which students learn something during a

course but aren’t qualified to use it when certified. The only exceptions

are certifications planned for gaining experience and then continuing in

training, such as the Apprentice Tec Diver course.

DSAT Tec Trimix Diver Course GoalsThe DSAT Tec Trimix Diver course is intended for technical divers certified as DSAT

Tec Deep Divers (or qualifying certification from another training organization). The

course extends their depth range capabilities by training them in the use of trimix

(helium, oxygen and nitrogen). It’s goals are:

• To qualify the student to dive to 75 metres/245 feet using various trimix

blends, air, enriched air and oxy-

gen, using open circuit technical

diving equipment and procedures

required to manage the risks

involved.

• To train the student in the cogni-

tive and motor skills required for

technical trimix diving.

• To assure the student acknowl-

edges and understands the hazards

and risks of technical diving in

general and trimix diving in partic-

ular, as well as the limits of train-

ing received in the course.

• To train the student to prepare for

and respond to reasonably foresee-

able emergencies that may occur in

this type of technical diving.

• To provide skills applicable to further training and experience in tech-

nical diving.

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Course OverviewThe DSAT Tec Trimix Diver course applies the same performance-based instructional

system methodologies that PADI Instructors learn to use and apply in the PADI

Instructor Development Course (IDC). However, the knowledge development training

dives within the system are at the level appropriate for technical trimix diving.

Knowledge DevelopmentTechnical diving in general requires mastering significantly more procedural knowl-

edge and applied theory than in recreational diving, and trimix diving increases these

demands further. The Tec Trimix Diver course develops this knowledge through

independent student study with the Tec Trimix Diver Manual (required if available in

a language the student can understand), through application in knowledge develop-

ment sessions, and through application during training dive briefings, planning and

execution. (If the manual is not available in a language the student can understand,

knowledge development must be accomplished via lectures using the Tec Trimix

Lesson Guides.)

As with the Tec Deep Diver course, this course divides several topics into multi-

ple presentations sequenced amid the appropriate training dives. This enhances

learning because students study, apply and assimilate each topic in stages. Exercises,

knowledge reviews and exams provide tools for developing and assessing mastery at

each stage. You also assess mastery by noting student application of this knowledge

during the training dives.

The Tec Trimix Diver course builds upon the foundation laid by the Tec Deep

Diver course. The Knowledge Development required is therefore less extensive, and

oriented primarily to review and applying previously acquired

concepts to trimix diving. New material relates primarily to the

aspects of trimix diving that differ from diving with air and

enriched air. Students who demonstrate knowledge deficiencies

need remedial attention and must demonstrate mastery prior to

continuing in the Tec Trimix Diver course. If necessary, it is

appropriate to have the student repeat all or portions of the Tec

Deep Diver course prior to continuing with the Tec Trimix Diver

course.

Training DivesThe Tec Trimix Diver course refines the skills learned in the Tec

Deep Diver course, then expands upon them with knowledge

application through sequenced training dives. The dives begin in

limited open water (see Section Two: Course Standards for the

specifics on what qualifies as limited open water). Open water

dives follow, progressing from air/enriched air dives to trimix

dives.

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The dives apply material from previous knowledge development and builds upon

previous skill development. The general intent is to first develop skills independently,

next integrate and apply them in simulated trimix dives, and finally apply them in actu-

al trimix dives.

Although the material is sequenced and loaded to match the learning abilities

expected of most divers, some individuals may need more time to meet performance

requirements. As necessary you may repeat sessions, dives or portions of them, until

students meet all performance requirements. Section Two: Course Standards, defines

mastery for this course.

Most of the core skills needed for trimix diving apply also to tec diving in general.

With this in mind, it’s essential that students have retained mastery from the Tec Deep

Diver course. The Tec Trimix Diver course builds upon these skills. You will be review-

ing them and checking for retention and mastery. Students who demonstrate signifi-

cant skill weakness need remediation to mastery levels prior to continuing in the

Tec Trimix Diver course. If necessary, it is appropriate to have the student repeat all

or portions of the Tec Deep Diver course prior to continuing with the Tec Trimix Diver

course.

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Instructor Guide Section TWO: Course Standards

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Section TWO: Course StandardsThis section includes the general course standards, recommendations and

suggestions for conducting the DSAT Tec Trimix Diver course. Course standards that

you must follow appear in boldface to clearly separate them from supporting mate-

rial and suggestions. For readibility headers appear in bold-

face; this doesn’t imply that everything under such a header

is required by standards. Course standards appear as bold-

face statements or distinct line items within this guide.

Legal and RegulatoryConsiderationsDSAT TecRec programs, including the DSAT Tec Trimix Diver

course, are made available to qualified PADI Members in

more than 175 countries and territories. Be aware that in

some regions, regulations and laws may impose restrictions,

requirements and prohibitions regarding diving, diving as an

employee, diving for any form of compensation or all of

these. Because it involves decompression diving and depths

beyond 40 metres/130 feet, technical diving may fall under

commercial diving regulations in some jurisdictions. This is

particularly true of trimix diving, which may fall under mixed

gas diving requirements.

It is your responsibility to be aware of and follow any local regulations that

apply to recreational and technical diving and to teaching recreational and techni-

cal diving. Be aware that regulations may exist on a federal, state/provincial, county

or city level.

_____ I understand that I AM SOLELY RESPONSIBLE FOR ENSURING MY OWN SAFETY DURING

PARTICIPATION IN THIS ACTIVITY and agree that: 1) the facility(ies), organization(s) or supervisory

personnel offering this activity, ___________________, or their employees; 2) the organizers or

promoters of this event; 3) Diving Science and Technology Corp. (DSAT); and 4) International PADI

Inc. (PADI), its affiliate or subsidiary corporations, any of their respective employees, officers,

agents or assigns (1 through 4 hereinafter referred to as "Released Parties"), may not be held liable

or responsible in any way for any injury, death or other damages to me or my family, heirs, or

assigns, that may occur as a result of my participation in this activity, or as a result of the negligence

of any party, including the Released Parties, whether passive or active._____ I declare that I am in good mental and physical fitness for diving, that I am not under the

influence of alcohol, nor am I under the influence of any drugs that are contraindicated to diving. If

I am taking any medication, I declare that I have seen a physician and have approval to dive under

the conditions of this activity while under the influence of the medication/drugs._____ I understand that all types of scuba diving, including Technical Diving, are physically strenu-

ous activities and that I will be exerting myself during this activity; and if I am injured as a result of

heart attack, panic, hyperventilation, etc. that I assume the risk of said injuries and that I will not

hold the Released Parties responsible for the same._____ I will inspect all of my equipment prior to every use during this activity, ensuring that I have

all necessary equipment, and that it is functioning properly. I will not hold the Released Parties

responsible for my failure to inspect my equipment prior to diving._____ I further save and hold harmless the Released Parties from any claim or lawsuit for personal

injury, property damage or wrongful death, by me, my family, estate, heirs, or assigns, arising out of

my participation in this activity, including both claims arising during the activity or after I complete

the activity.

_____ I further declare that I am of lawful age and legally competent to sign this liability release,

or that I have acquired the written consent of my parent or guardian. I further agree that if any por-

tion of this Agreement is held to be invalid for any reason that the remaining provisions shall

remain in full force and effect.

I, ______________________________________, understand and agree that the terms herein

are contractual and not a mere recital, that this instrument is a legally binding document,

and that I have signed this document of my own free act, after reading and understanding

the entire Liability Release and Express Assumption of Risk agreement.__________________ _______________________________________________________

(Date)

(Signature of Participant)

__________________ _______________________________________________________

(Date)

(Signature of Parent or Guardian if applicable)

__________________ _______________________________________________________

(Date)

(Witness)

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G Product No. 10266 Version 1.1 (07/03)

© International PADI, Inc. 2003

Liability Release and Express Assumption of Risk

for Technical Diving

Please read carefully, fill in all blanks and initial each paragraph before signing.

I, _________________________________________, HEREBY DECLARE THAT I AM A CERTIFIED

(Participant)

SCUBA DIVER, TRAINED IN SAFE DIVING PRACTICES INCLUDING THE USE OF NITROX, AND AM

AWARE OF THE INHERENT HAZARDS OF SCUBA DIVING.

_____ I further state that I am an experienced diver and have been certified by the following

training organization(s): ____________________________ and that I am aware of the required

certification or equivalent experience required to participate in technical diving activities. I have

been a certified diver since __________, and have been diving for ________ years, with a total of

approximately ________ dives, to a maximum depth of _________ metres/feet (circle one).

_____ I further declare that I have been advised and thoroughly informed of the inherent hazards

of participating in technical and recreational scuba diving activities, and in consideration of being

allowed to participate in this activity, I hereby assume all risks in connection with said activity, for

any harm, injury or damage that I may suffer while I am participating in this activity, including all

risks connected therewith, whether foreseen or unforeseen.

_____ I further declare that I am properly trained, thoroughly informed, and completely under-

stand the inherent hazards of Technical Scuba Diving activities, including the risk of serious injury

or death. Further, I understand that diving with compressed air, oxygen-enriched air (nitrox) trimix,

and 100 percent oxygen involves certain inherent risks that include but are not limited to: decom-

pression sickness, embolism, oxygen toxicity, inert gas narcosis, marine life injuries, fire and/or

explosion hazards, and barotrauma or hyperbaric injuries which can occur and require treatment

in a recompression chamber. I further understand that Technical Scuba Diving activities may be

conducted at a site that is remote, either by time or distance or both, from such a recompression

chamber. I still choose to participate in such Technical Scuba Diving activities, despite the possi-

ble absence of a recompression chamber in proximity to the dive site.

_____ I further declare that I understand Technical Diving involves risks which exceed those

encountered in recreational scuba diving. These risks may include but are not limited to: depths

which exceed the limits of recreational diving; decompression procedures; over-head environ-

ments and/or the risk of entanglement which may prevent direct ascent to the surface in the event

of an emergency; sudden loss of visibility; necessity for computing both nitrogen and oxygen

loading to plan dives; and the need for specialized training, equipment, and planning for different

types of Technical Scuba Diving. I understand that Technical Scuba Diving may involve a greater

risk of serious injury or death than recreational scuba diving, and I assume the risk of this activity.

Section TWO: Course Standards Instructor Guide

Instructor RequirementsTo conduct the Tec Trimix Diver course, you must be a renewed, teaching status

PADI Instructor who is certified as a DSAT Tec Trimix Instructor.

Qualifying as a DSAT Tec Trimix Instructor is similar to, but not identical to, quali-

fying as a DSAT Tec Deep Instructor. You may qualify by successfully completing a

DSAT Tec Trimix Instructor Training course conducted by a PADI Course Director who

is certified as a Tec Trimix Instructor Trainer, or by applying directly to PADI. In both

cases you must meet the minimum requirements listed.

Requirements to Qualify Through a DSAT Tec Trimix Instructor Training CourseTo enroll in a DSAT Tec Trimix Instructor Training course, you must meet the

following criteria:

1. Be a renewed PADI Master Scuba Diver

Trainer or higher level PADI Instructor.

2. Be a DSAT Tec Deep Instructor, or have

successfully completed the DSAT Tec Deep

Instructor Training Course including the

instructor examinations.

3. Be certified as a DSAT Tec Trimix Diver or

have a qualifying full trimix certification

from another organization. (Contact your

PADI Office for information about qualifying

certifications)

4. Have a minimum of 200 logged dives, with

at least 20 technical decompression dives

requiring at least one stage/deco cylinder.

Of these, at least 10 must have been made deeper than 40 metres/130

feet using trimix.

Upon successfully completing the DSAT Tec Trimix Instructor Training course,

before sending your application to PADI, you must meet the following criteria:

1. Be a renewed PADI Master Scuba Diver Trainer or higher level PADI

Instructor who is a DSAT Tec Deep Instructor.

2. Be certified as a DSAT Tec Trimix Diver or have a qualifying full trimix

certification from another organization. (Contact your PADI Office for

information about qualifying certifications.)

3. Have assisted with at least one Tec Trimix Diver course. If you have a

qualifying certification as a trimix instructor with an other organization,

having taught or assisted with one of those courses meets this require-

ment. (Contact your PADI Office for information about qualifying certifica-

tions.)

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4. Have a minimum of 350 logged dives, with at least 50 decompression

dives deeper than 40 metres/130 feet beyond those required for certifi-

cation as a technical diver. At least 30 must be deeper than 40

metres/130 feet using trimix as the bottom gas, with at least 10 of these

deeper than 50 metres/165 feet using trimix with less than 21 percent

oxygen.

5. Have successfully completed the Tec Trimix Instructor Standards Exam

and Tec Trimix Instructor Theory and Practical Application Exam.

6. Be 21 years old.

Your application must include documentation or other proof of meeting these

requirements by including photocopies of certifications, qualifications, etc. Log

entry copies or print outs must specify dates, depths, location, times and gases

used. Verification and signatures provided by witnesses (divers and instructors of

courses assisted) must provide the same information. See the DSAT Tec Trimix

Instructor Application in the Appendix for details on documentation requirements.

Requirements to Qualify by Applying Directly to PADITo apply directly to PADI for certification as a DSAT Tec Trimix Instructor,

you must meet the following criteria:

1. Be a renewed PADI Master Scuba Diver Trainer or higher

level PADI Instructor who is a DSAT Tec Deep

Instructor.

2. Be certified as a DSAT Tec Trimix Diver or have

a qualifying full trimix certification from anoth-

er organization. (Contact your PADI Office for

information about qualifying certifications.)

3. Have assisted with at least one Tec Trimix Diver

course. If you have a qualifying certification as

a trimix instructor with an other organization,

having taught or assisted with one of those

courses meets this requirement. (Contact your

PADI Office for information about qualifying certi-

fications.)

4. Have a minimum of 350 logged dives, with at

least 50 decompression dives deeper than 40

metres/130 feet beyond those required for cer-

tification as a technical diver. At least 30 must be deeper than 40

metres/130 feet using trimix as the bottom gas, with at least 10 of these

deeper than 50 metres/165 feet using trimix with less than 21 percent

oxygen.

5. Have successfully completed the Tec Trimix Instructor Standards Exam

and Tec Trimix Instructor Theory and Practical Application Exam.

6. Be 21 years old.

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Applicant AcknowledgementI certify that the information contained here is true and correct to the best of my knowledge and

understand that this certification is subject to approval by PADI.Applicant Signature_______________________________________________ Date___________________Signature

Day/Month/Year

Instructor Signatures: The verifying Instructors must be a DSAT Tec Trimix Instructor or a PADI Instructor

with a qualifying certification.

Logged Dive Verification: I have verified that the applicant has logged at least 350 dives with at least 50 decompres-

sion dives deeper than 40 metres/130 feet, not including those required for certification as a technical diver.

Verifying Instructor _____________________________________ PADI No. _______________ Date ___________________

Signature

Day/Month/Year

Logged Trimix Diver Verification: I have verified that the applicant has logged at least 30 dives deeper than 40

metres/130 feet using trimix as the bottom gas, with at least 10 of these dives deeper than 50 metres/165 feet using trimix

with less than 21 percent oxygen.Verifying Instructor _____________________________________ PADI No. _______________ Date ___________________

Signature

Day/Month/Year

Course Assistance Verification: I have verified that the applicant has assisted with at least one DSAT Tec Trimix Diver

course.* If applicant has a qualifying certification as a trimix instructor with another organization, having taught or assisted

with one of those courses meets this requirement. (Contact your PADI office for information about qualifying certifications

and proper documentation.)Verifying Instructor _____________________________________ PADI No. _______________ Date ___________________

Signature

Day/Month/Year

Tec Trimix Instructor Exams: I have verified that the applicant has successfully completed the Tec Trimix Instructor

Standards Exam and Tec Trimix Instructor Theory and Practical Application Exam.Verifying Instructor _____________________________________ PADI No. _______________ Date ___________________

Signature

Day/Month/Year

If Applicable:Dive Center/Resort Name ____________________________________ Store No. ___________ Phone (_____)___________ *When meeting this requirement by qualifying certification enclose a copy of your trimix instructor certification and

contact your local PADI Office regarding any additional required documents.

TEC TRIMIX INSTRUCTOR APPLICATION

PLEASE PRINT OR TYPE

□ Check here if this is a change of address

Name_____________________________________________________________ PADI No. _____________________

FirstInitial

Last

Mailing Address __________________________________________________________________________________

City____________________________________________________ State/Province____________________________

Country__________________________________________ Zip/Postal Code _________________________________

Home Phone (______) ___________________________ Business Phone (______) ____________________________

Fax (_____) _____________________________ Email Address ____________________________________________

Sex: □ M □ F Birthdate _____________________ Occupation _____________________________________

Day/Month/Year

Requirements: To apply for the DSAT Tec Trimix Instructor rating you must meet the following requirements.

Refer to the DSAT Tec Trimix Diver Instructor Guide for specifics. Direct questions on qualifying certifications to

the PADI Training and Quality Management Department.

□ PADI Master Scuba Diver Trainer (or higher) Rating □ DSAT Tec Trimix Diver (or qualifying certification*)

□ DSAT Tec Deep Instructor□ I am at least 21 years old.

* If submitting qualifying certification from another training organization, please be sure to attach photocopies of the certification.

PAYMENT METHOD

Application Fee____________________________ � Check No._________________________

Check for PADI Americas only – Must be payable to PADI in US dollars, and drawn on a US bank.

� American Express � Discover Card � MasterCard � VISA � JCB

Switch/Solo Issue No. ___________________________ (Not Valid in USA)

Expiration Date ______________________ (Valid from Date – UK Only) __________________

Card No. ________________ ________________ ________________ ________________

Cardholder Name ________________________________________________________________

Please Print

Authorized Signature _______________________________________________________

Cardholder Address _______________________________________________________

(If different from applicant.)

_______________________________________________________________________________________________________________________

MAIL TO YOUR PADI OFFICE

Attn: DSAT Tec Trimix Instructor Certification

See current price list for mailing information. Please be sure to

enclose all required materials (see checklist).

Rec’d ________________________ Ent ______________________

Shp’d________________________

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Tape/Attach a

4.5cm x 5.7cm

1.75” x 2.25”

Head-and-Shoulders Photo

PRINT NAME ON

BACK OF PHOTO

Coin machine photos OK

Do not send old cards

NO DARK GLASSES

CHECKLIST

□ Application filled-in completely

□ Requirements completed

□ Successfully completed Tec Trimix

Standards and Theory/Practical Exams

□ Verification of logged dives

□ Verification of course assistance

□ Enclosed processing fee (see current price list)

□ Applicant and Instructor signatures

OFFICE USE ONLY

Reviewer _______________________ Certification Date _________________

G Product No. 10170 Version 1.0 (07/03)



Your application must include documentation or other proof of meeting these

requirements by including photocopies of certifications, qualifications, etc. Log

entry copies or print outs must specify dates, depths, location, times and gases

used. Verification and signatures provided by witnesses (divers and instructors of

courses assisted) must provide the same information. See the DSAT Tec Trimix

Instructor Application in the Appendix for details on documentation requirements.

Certified Assistant RequirementsTo qualify as a certified assistant for any dives of the DSAT Tec Trimix Diver course,

an individual must:

1. Be a renewed PADI Divemaster or higher level PADI Member.

2. Be a PADI Enriched Air Diver.

3. Be a DSAT Tec Trimix Diver or have a qualifying full

trimix certification from another training organiza-

tion. (Contact your PADI Office for information about

qualifying certifications.)

4. Have made at least 250 dives, with at least 40 tech-

nical decompression dives deeper than 40 metres/

130 feet of which at least 20 are trimix decompres-

sion dives, beyond those required for certification.

The individual must also have experience diving

with trimix to the actual depth of each training dive.

5. Be 18 years old.

To qualify as a certified assistant for only the Assessment Dive

and Training Dives One through Three, an individual must:

1. Be a renewed PADI Divemaster or higher level PADI

Member.


3. Be a DSAT Tec Trimix Diver or have a qualifying full trimix certification

from another training organization. (Contact your PADI Office for informa-

tion about qualifying certifications.)

4. Have made at least 20 technical decompression dives to 40 metres/130

feet or deeper, beyond those required for certification.

5. Be 18 years old.

To qualify as a certified assistant for only the Assessment Dive and Training Dive

One, an individual must:

1. Be a renewed PADI Divemaster or higher level PADI Member.


3. Be a DSAT Tec Deep Diver or have a qualifying technical air/enriched air

deep diving certification from another training organization. (Contact

your PADI Office for information about qualifying certifications.)

4. Be 18 years old.

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Course PrerequisitesPrerequisites for the DSAT Tec Trimix Diver course establish the minimums for

entering the course. It is your responsibility to ensure that the student meets the

prerequisites, through remedial work if necessary, before starting the course. It’s

recommended that you preassess potential students’ skill and knowledge in a con-

fined water session and/or discussions that apply what they know. You can combine

remediation with preassessment, refreshing student capabilities to mastery prior to

beginning the Tec Trimix Diver course.

Before starting the Tec Trimix Diver course,

students must meet the following prerequisites.

1. Certified as a PADI Rescue Diver or

have a qualifying certification in diver

rescue and accident management

from another organization. (Contact

your PADI Office for information about

qualifying certifications.) Students who

meet this through a qualifying

nonPADI certification need to provide

proof of CPR and first aid training

within the previous two years.

2. Minimum age: 18 years

3. Certified as a DSAT Tec Deep Diver or

have a qualifying certification in deep decompression diving using

air/enriched air from another organization. (Contact your PADI Office for

information about qualifying certifications.) Students who qualify

through a qualifying certification other than DSAT Tec Deep Diver must

read the entire DSAT Tec Deep Diver Manual and complete the

Knowledge Reviews prior to beginning the Tec Trimix Diver course.

(See the section on Knowledge Development Preassessment.) This require-

ment is to assure student familiarity with TecRec philosophies and

methodologies, as well as to refresh their knowledge.

4. Have a minimum of 150 logged dives.

Equipment RequirementsDuring the DSAT Tec Trimix Diver course, students and instructional staff (exclud-

ing staff functioning solely as support diver for the decompression/simulated

decompression phase of the dives) must be fully equipped in technical diving gear,

meeting the philosophies and intent described in the course presentation outlines

(see Section Three), the DSAT Tec Deep Diver Manual and the DSAT Tec Trimix

Diver Manual. This course is performed with open circuit equipment that includes,

per diver, but is not necessarily limited to:

• Double cylinders (minimum 12 l/70 cf each, with larger preferred) with

isolator manifold

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• Primary and secondary regulators, one with two metre/seven foot hose

(approx.) for gas sharing, and one with SPG

• Stage/decompression cylinders with regulator, SPG, mounting hardware

and proper labeling/markings. Two per diver will be required

• Backup decompression cylinders as appropriate and required for the

environment

• BCD and harness – redundant buoyancy control is required (double

bladder BCD or dry suit if suitable for weight

of equipment worn)

• Depth gauge/computer and backup depth

gauge/computer

• Timing device and backup timing device

• Trimix decompression information (tables/

trimix computer) and backup decompression

information

• Exposure suit appropriate for environment and

dive duration. (If students will use dry suits,

they should be trained/experienced with their

use in recreational and technical diving prior

to using them for trimix training or diving.)

• Argon dry suit inflation or other inflation system

as needed (students should not inflate dry suit

with trimix)

• Weight system (if needed)

• Jon line (if needed for current diving environ-

ments)

• Inflatable signal tube

• Reel

• Lift bag (bright yellow or per local community practice preferred)

• Knife/cutting device and backup

• Slate

• Backup mask (optional)

• Compass

• Lights (optional)

• Drift kit (if drift decompressing)

The following equipment should be available for practical use by all students and

instructional staff, though one per individual is not required. Items not in boldface

are recommended but not required.

• Computer with trimix capable decompression software and printer

Portable to dive site recommended

• Laminator (for laminating tables)

• Oxygen analyzer

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• Helium analyzer

• Ascent/descent line(s) from boat/float as necessary

• First aid kit

• Emergency oxygen

It’s recommended that you bring spare clips, pull ties, tank wraps, labels, tape and

other rigging accessories for assisting students with equipment configuration refine-

ments and adjustments. Students at this level should have their technical equipment

refined and set, but minor adjustments aren’t unusual.

Students may not use closed circuit or semiclosed circuit scuba in the Tec

Trimix Diver course.

Instructor MaterialsMaterials required by standards are identified in boldface.

You may find the optional materials useful when conduct-

ing the course as well.

• DSAT Tec Trimix Diver Manual

• DSAT Tec Trimix Diver Instructor Guide

• DSAT Tec Deep Diver Manual

• DSAT Tec Deep Diver Instructor Guide

• TecRec Equipment Setup and Key Skills video

• PADI Enriched Air Diver Manual

• PADI Enriched Air Diver video

• DSAT Tec Trimix Diver Lesson Guides

• Enriched air cylinder decal

• Contents stickers

• Enriched air fill log sheets

• DSAT Tec Trimix Diver Exams and answer sheets

• DSAT Tec Deep Diver Exams and answer sheets

• Enriched Air Diver Exam and answer sheets

• Tec Trimix Diver Statement of Understanding and Learning Agreement

• PADI Diver Protection Program enrollment forms

• TecRec Dive Planning Slate

• TecRec Dive Planning Checklist slates

• DSAT Tec Trimix Diver Instructor Cue Cards

• DSAT TecRec Deep Stop Calculation Table slate

Student MaterialsBecause technical trimix diving requires a large knowledge development load,

student divers in the DSAT Tec Trimix Diver course are required to have personal

copies of the Tec Trimix Diver Manual and the Tec Deep Diver Manual unless the

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Manual

TEC TRIMIXDIVER

TEC TRIMIXDIVER


manuals are not available in a language the student diver understands. In that

case, you provide course information through class sessions, predive briefings, etc.

Students use the manual for independent study, and for reference and review of the

tables during diving planning both during the course and after certification. The fol-

lowing materials may also be used for study, remediation or additional information.

• PADI Enriched Air Diver Manual

• Encyclopedia of Recreational Diving (book or CD-ROM)

• “Oxygen Exposure Management,” by Dr. R. Vann in Proceedings ofRebreather Forum 2.0

• NOAA Diving Manual, Fourth Edition

• PADI Divemaster Manual, current edition

• Computer with trimix capable decompression software

• TecRec Dive Planning Slate

• TecRec Dive Planning Checklist slates

• TecRec Deep Stop Calculation Table slate

Paperwork and AdministrationStudent divers in the Tec Trimix Diver course must complete the

following paperwork before beginning any inwater training.

• Liability Release and Express Assumption of Risk for

Technical Diving

• Tec Trimix Diver Statement of Understanding and

Learning Agreement

• Medical Statement. Prior to Training Dive One, the

student must have a physician’s approval and signature

on the Medical Statement, even if the student answers

“no” to all medical conditions listed. If the student

received a physician’s approval and signature on a

Medical Statement within the last year and has had

no medical condition change, and if you have that

Medical Statement on file, then the student diver does

not need to see a physician again.

Insurance RequirementsWhen teaching the DSAT Tec Trimix Diver course, DSAT Tec Trimix Instructors

must have professional liability insurance that does not exclude diving deeper

than 40 metres/130 feet, making planned decompression dives, or using enriched

air, oxygen or helium blends. This does not apply in areas that are excluded by

your PADI Office. If not required in your area, it’s always recommended. Some insur-

ance policies may require an endorsement or other special provision to provide cov-

erage. Check with your PADI Office if you’re unsure about your professional liability

insurance requirements or whether your policy provides the appropriate coverage.

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It’s recommended that students enrolled in the Tec Trimix Diver course carry

diver medical insurance such as the PADI Diver Protection Program, Platinum, or other

dive accident insurance that provides coverage for medical care following a dive acci-

dent, including recompression and transportation, without exclusions for coverage

due to depth or gases used.

Certification ProceduresWhen the student successfully completes all the Tec Trimix Diver course require-

ments, the instructor who conducts the final open water dive and evaluates final

student performance issues the certification by submitting a completed PIC enve-

lope to the appropriate PADI Office.

Course Sequence and Preassessment RequirementsThe DSAT Tec Trimix Diver course structure applies educational and learning princi-

ples based on how people acquire, store, organize and later retrieve and use what

they learn. The structure avoids dumping everything about a

single topic in one session with the expectation that students

will learn it. When developing an extensive knowledge frame-

work, as in this course, such an approach neglects developing

the mental structures that people use to effectively store and

retrieve information. The “dump it all on them at once”

approach doesn’t permit topics and motor skills to integrate

efficiently, making it hard for students to recognize and under-

stand the interrelationships. This interferes with developing

seamless motor skills and procedures that draw upon interre-

lated information.

Instead, the DSAT Tec Trimix Diver course structure

sequences information to introduce multiple topics at once.

The course covers each topic in steps, gradually building

depth and integrating them, with recall, application and rein-

forcement in the corresponding training dive(s). This creates a

learning pyramid similar to those applied to PADI programs.

For the Tec Trimix Diver course, the sequence is:

1. Student diver studies assigned section of the DSAT Tec Trimix Diver

Manual, answering the Tec Exercises throughout.

2. Student completes the Knowledge Review at the end of the section.

3. Instructor reviews the Knowledge Review for completeness and accuracy.

4. Using the Tec Trimix Lesson Guides as appropriate, instructor provides

remedial training in weak areas, reviews and reinforces key points and

has student apply material during Practical Application (briefings and/or

class sessions).

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5. Student recalls and applies material in the section’s Training Dive(s),

meeting performance requirements specific to the material and previous-

ly learned principles.

6. After completing the Knowledge Development sections, the diver com-

pletes the Tec Trimix Diver Examination.

7. Student diver reviews any questions missed with the instructor.

Because the instructional design depends upon building knowledge and skills in

sequence, the student must complete Knowledge Development sections in order,

and meet all performance requirements for each prior to the corresponding

Practical Applications and Training Dive(s) as sequenced in the course outline

(Section Three). The student diver must complete all Practical Applications in

order, and meet all the performance requirements for each

prior to the corresponding Training Dive(s). The student

diver must complete all Training Dives in order, and meet all

performance requirements for each Training Dive prior to

progressing to the next Training Dive.

Students may continue into the next Knowledge

Development section and corresponding Practical Application

before completing the dives that correspond with the previous

Knowledge Development section. It’s recommended that you

have students review material covered previously if there’s

more than a few days interval between completing a

Knowledge Development section and Practical Application and

the corresponding Training Dive(s).

Section Three, the course outline, sequences Knowledge

Development sections, Practical Applications and Training

Dives in their required order.

Knowledge DevelopmentPreassessmentBecause knowledge development in the Tec Trimix Diver

course builds on the foundation laid by the Tec Deep Diver course, student divers

must be able to meet the knowledge development (and motor skill) performance

requirements of that course prior to beginning the Tec Trimix Diver course. It is your

responsibility to assess student knowledge retention prior to beginning the Tec Trimix

Diver course. To accomplish this:

1. Students who qualify through a qualifying certification other than DSAT

Tec Deep Diver must read the entire DSAT Tec Deep Diver Manual and

complete the Knowledge Reviews prior to beginning the Tec Trimix

Diver course. You must review them for completeness and accuracy, pro-

viding remedial training as necessary. If the manual is not available in a

language the student can read, the student must still complete the

Knowledge Reviews for your review and remedial training as necessary.

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2. Assess Tec Deep Diver certified students with one of the following methods:

• Review their Knowledge Reviews and exam answer sheets from the

Tec Deep Diver course, confirming retention, mastery of problem

areas and providing remedial training as necessary.

• If the Knowledge Reviews are unavailable, have them complete the

following Knowledge Review questions from the Tec Deep Diver

Manual:

– Knowledge Review Chapter One, Questions 2, 10

– Knowledge Review Chapter Two, Questions 2, 11, 14, 23, 24, 25

– Knowledge Review Chapter Three, Questions 3, 5, 13, 18

– Knowledge Review Chapter Four, Questions 7, 10, 11

– Knowledge Review Chapter Five, Questions 1, 2

– Knowledge Review, Chapter Six, Questions 6, 7

• Have the student complete Tec Deep Diver Exam 2.

Any deficient areas require remedial training until the student demonstrates mas-

tery prior to beginning the Tec Trimix Diver course.

Training Dive StandardsThe following standards apply to all inwater training in the Tec Trimix Diver course.

Confined and Limited Open WaterYou must conduct Training Dive One in confined water or

limited open water. This dive focuses on reviewing and

refining existing technical diving procedures and motor

skills in preparation for trimix diving, and introducing new

motor skills specific to trimix diving. The philosophy is to

minimize environmental influences and allow the student

to focus on equipment and procedures.

Definition of Confined WaterFor the purposes of the Tec Trimix Diver course, con-

fined water is defined as either a swimming pool, or an

open water site that offers swimming-pool-like conditions

with respect to water motion (waves/current) and depth,

with a minimum depth of 2.5 metres/8 feet.

Definition of Limited Open WaterBecause Tec Trimix Diver students have extensive training and experience behind

them, you may conduct Training Dive One in limited open water. For the purposes of

the Tec Trimix Diver course, limited open water is defined as an open water site,

fresh or salt, no deeper than 10 metres/33 feet. A platform or other bottom that is

10 metres/33 feet or shallower in otherwise deeper water meets this requirement if it

provides ample space to meet the performance requirements and for control. There

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should be no appreciable current or significant waves.

There should be direct access to the surface and suffi-

cient visibility to not negatively affect student comfort or

skill development. Conditions should be sufficiently calm

and temperature sufficiently warm such that they are not

significant factors. It’s often helpful, but not essential, to

have water shallow enough to stand up in immediately

available for briefing/debriefing.

In opting to use limited open water, keep in mind that

the goal is to permit student divers to concentrate on their

equipment and developing motor skills and procedural

skills. Such a site must have access to an insensitive bot-

tom because bottom contact is likely to be frequent. If

there’s any question about student familiarity with the

environment, it’s a good idea to orient them to the site with

an orientation dive prior to the training dives.

Open Water Training StandardsFor the purposes of the Tec Trimix Diver course, open water is defined as a body of

water considerably larger than a swimming pool with the adequate depth and con-

ditions for meeting the performance requirements of each training dive. The envi-

ronment may have no physical overhead barriers that prohibit a direct vertical

ascent. These may include, but are not limited to, the ocean, lakes, springs and

quarries. Student divers should be confident they can handle the demands imposed

by the environment while applying and mastering the required procedures and motor

skills. Qualified instructors following the Cave Environment Training Option with

qualified students (see that section in this guide) are permitted to train in the cave

environment, but must still have access to adequate open water to complete the

required open water skills for each training dive.

Ratios and DepthsThe ratios, minimum depths and maximum depths vary for Training Dives One

through Eight. Follow the ratio and depth requirements, which change with the dive,

as listed in each training dive outlined in Section Three. A summary of all the dive

requirements appears in the Appendix. Ratios listed are for optimum circumstances –

reduce ratios for less than optimum conditions, to meet student needs or to accommo-

date other considerations. All dives require direct supervision by the instructor

(and assistant as required) in the ratios listed. Although divers at the Tec Trimix

Diver level will conduct most of their dives with minimal instructor direction, the

instructor must be present to observe and assess performance and to provide assis-

tance if necessary. All ratios listed for this course are for optimum circumstances

(e.g., good visibility, minimal current or waves, students with high aptitude, etc.).

Reduce the ratio as necessary for adequate control based on logistical, environmen-

tal and instructional needs.

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Gas PlanningGas planning for each training dive with the accepted reserve for each diver (usually

thirds) is an integral part of training. The philosophy continues from the Tec Deep

Diver course that you plan your reserve based on all the required gas, including back

gas used for decompression. Given the depths involved in trimix diving, depending

upon the environment, instructors and staff may want to plan larger than normal

reserves to provide extra gas for handling problems. It’s recognized this may or may

not be feasible or reasonable depending upon the circumstances.

Drift Dive EnvironmentsThe technical diving community differs widely in the protocols for decompressing in

drift situations. The Tec Trimix Diver course includes lift bag drills and decompression

practice, but in many dive environments this is the backup procedure rather than the

primary procedure for decompressing, even with a current.

Unless doing so would be unsafe, when drift diving from a boat it’s recommended that

divers have a rope ascent line and float or marker that assists the boat in tracking the

divers throughout the dive. Lift bag skills may be practiced along this line with staff

controlling it if necessary while students handle the lift bag. It’s recommended that

student divers and instructional staff carry drift kits as

described in the Tec Deep Diver Manual and/or as used in

the local environment.

Water Skills AssessmentStudents entering the course with a qualifying certifica-

tion other than the Tec Deep Diver certification and

those with Tec Deep Diver certification who have not

logged a technical decompression dive requiring a

decompression cylinder to 40 metres/130 feet or deeper

in the previous six months must successfully complete

the Assessment Dive. (See Section Three, V. Assessment

Dive.) You may conduct the Assessment Dive in confined

water, limited open water or open water.

Definitions of MasteryTrimix divers need a high mastery level with respect to dive theory and dive skills.

The definitions of mastery in this course reflect this.

For knowledge development, mastery is defined as scoring 80 percent or higher

on the exam. The student must review any items missed until attaining complete

understanding. Students who score lower than 80 percent must retake the entire

exam. The student must complete all Knowledge Reviews accurately (revising and

correcting after remediation when necessary). The student must demonstrate accu-

rate, adequate knowledge application in all Practical Applications and during the

Training Dives. You may additionally assess knowledge through impromptu questions

or assignments.

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Skill development mastery is defined as performing all skills (procedures and

motor skills) fluidly, with little difficulty, in a manner that demonstrates minimal or

no stress. You may allow for the task loading imposed in each situation when judging

stress, bearing in mind that student divers need to perform

all routine and emergency skills and procedures in a man-

ner that leaves no reasonable doubt that they could reliably

perform them as required when diving independently.

For certification, the mastery requirements extend to

all prerequisite recreational and technical diving skills

and procedures. If a student diver has difficulty with any

prerequisite skill, whether it’s stage bottle handling or mask

clearing, the student must demonstrate mastery as defined

above prior to certification as a Tec Trimix Diver.

The Tec Trimix Diver course builds upon the foundation

laid by the Tec Deep Diver course. Therefore, a student

who demonstrates difficulty with prerequisite Tec Deep

Diver knowledge or skills requires remediation before

continuing in the Tec Trimix Diver course. Students

should not be learning knowledge or skills in the Tec Trimix Diver course that they

should have previously mastered. If necessary, it is appropriate to have such students

repeat all or portions of the Tec Deep Diver course to reestablish mastery.

Optional Dives for Tec Deep DiversTraining Dive Two is optional for students who were certified as Tec Deep Divers

within the previous six months, or who are certified as Tec Deep Divers and have

logged at least one technical decompression dive to 40 metres/130 feet or deeper

using at least one decompression cylinder in the previous six months. You may, at

your discretion, require Tec Deep Divers complete Training Dive Two for additional

experience, skill assessment, refinement, logistics or other reasons as appropriate.

Training Dive Four is optional for students who are certified as Tec Deep

Divers.

Divers entering the Tec Trimix Diver course with a qualifying non DSAT prereq-

uisite certification must successfully complete all training dives as outlined. You

may, at your discretion, have Tec Deep Divers in the course complete Training Dive

Four for additional experience, skill assessment, refinement, logistics or other reasons

as appropriate.

Cave Environment Training OptionYou may conduct the DSAT Tec Trimix Diver course in cave diving environments if the

following conditions are also met.

Instructor Requirements1. The instructor must be certified as a DSAT Tec Trimix Instructor.

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2. The instructor must have a qualifying full cave instructor certification

from a qualifying cave diver training organization. (See your PADI Office

for more information about qualifying certifications and organizations.)

3. The instructor must have made at least 20 trimix dives in cave environ-

ments.

Certified Assistant Requirements1. The individual must meet the certified assistant requirements.

2. The individual must have a qualifying full cave diver certification from

a qualifying cave diver training organization. (See your PADI Office for

more information about qualifying certifications and organizations.)

3. To qualify as a certified assistant for Training Dives 3-8, the individual

must have made at least 20 trimix dives in cave environments.

Student Requirements1. The student must meet all other prerequisites and requirements for the

Tec Trimix Diver course.

2. The student must have a qualifying full cave diver certification from a

qualifying cave diver training organization. (See your PADI Office for

more information about qualifying certifications and organizations).

3. The student must have at least 60 cave dives logged,

not including any cave training dives.

Environment RequirementsCave environments used for the course must have sufficient

open water for all required course skills. This includes lift bag

deployment, neutrally buoyant gas shutdowns, deco stops

without bottom contact, etc.

Equipment and Gas Requirements1. Cave diving equipment configuration must be consis-

tent with the standardized technical rig. The light

canister is worn on the right hip to control the long

hose in place of the lift bag reel.

2. Open water skill-related equipment (lift bag, ascent line, etc.) may be

staged in the open water adjacent to the cave or just inside, etc. as appro-

priate. However, students must stow their open water equipment in

their rigs as it would normally be worn in open water prior to begin-

ning the open water skills. This is because retrieving and deploying the

equipment is part of skill mastery.

3. Gas selection follows the requirements for each dive in Section Three.

At no time shall the END exceed 40 metres/130 feet within the overhead

environment. Training Dive Two, if conducted in an overhead environ-

ment, may not exceed 40 metres/130 feet.

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Instructor Guide Section THREE: Course Outline

Section THREE: Course OutlineThis outline provides the content, structure and sequence for the DSAT Tec TrimixDiver course. Here you find recommendations for conduct, sequence and student per-formance requirements. The outlines for the Knowledge Development Presentationsappear in presentation format, written as you would deliver to your students. Notes toyou, the DSAT Tec Trimix Instructor, appear in brackets within these.

I. Course SequenceA. The outline matches the

required course sequence.B. Students must complete the

performance requirementsfor Knowledge Developmentsections in order.

C. Student divers must com-plete the performancerequirements for eachKnowledge Development sec-tion before the correspon-ding Practical Application.

D. Student divers must com-plete the performance requirements for all Knowledge Developmentsections and Practical Application sessions, including the exam, thatprecede a Training Dive in the outline. Note that the Assessment Dive(optional for Tec Deep Diver certified students) appears after KnowledgeDevelopment One and Practical Application One, but you may conduct itprior to those sessions, provided the students meet the course prerequi-sites, medical requirements, etc.

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Section THREE: Course Outline Instructor Guide

E. Students must complete the performance requirements for eachTraining Dive before progressing to the next Training Dive.

F. For schedule and logistics flexibility:1. Student divers may progress through Knowledge Development sections

and Practical Applications (in order) even ifthey have yet to complete the Training Dives.

2. Student divers may let their independentstudy in the Tec Trimix Diver Manual continueahead of the Knowledge Development andPractical Applications that they’ve completed.

II. Use of the Outline and MaterialsA. Use of the DSAT Tec Trimix Diver Manual is

required, unless it is not available in a lan-guage the student understands.1. Assign students the relevant sections to read

in the manual, answering the exercise ques-tions and completing the Knowledge Reviewsprior to each Knowledge Development presen-tation and Practical Application session.

2. If the manual is not available in a languagethe student understands, you must delivercontent through teaching presentations using the KnowledgeDevelopment presentation outlines and the Tec Trimix Diver LessonGuides. Keep in mind that this will require more time than listed in therecommended course hours. Student divers must still meet allKnowledge Development performance requirements and demon-strate mastery as described in Section Two. It’s recommended thatstudents have a personal copy of the manual even if they’re not avail-able in a language they can read to provide ready access to the tablesin its appendix. If they do not have the manual, you will need to pro-vide copies of these tables for their use during and after the course.

B. Although the Knowledge Development presentations cover all the contentrequirements for each Knowledge Development section, it’s recommend-ed that you use prescriptive teaching presentations, much like those youuse with PADI courses, based on the outlines.1. Review student Knowledge Reviews and then base your presentation

on areas that showed difficulty, on areas that require elaboration toadapt the material to local circumstances and student needs, and ontopics that you need to repeat for emphasis.

2. Knowledge Development leads to Practical Application, which givesstudent divers opportunities to apply what they’ve learned for practiceand to enhance future retention and recall. Because PracticalApplication draws upon previous Knowledge Development, it’s impor-tant to retrain students with knowledge difficulties before they beginthe Practical Application that follows.

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C. Practical Applications provide students with hands-on practice beforeactually applying concepts in dive planning and diving. In some cases,the Practical Applications apply as preparation for upcoming dives.You may assign Practical Applications as independent projects, thoughyou may find it advantageous to conduct them in group sessions.1. Keep guidance to a minimum, except

when student divers ask for or show thatthey need it. The idea is to let themdevelop the mental strategies for prob-lem solving and solution generation asthey tackle each task.

2. The Practical Applications direct stu-dents to work in teams, with the entire

team successful or not. As in the TecDeep Diver program, this is intended tobuild team-orientation and team planningas needed for technical trimix diving.Encourage students to assist each otherin mastering materials and in overcominglearning difficulties. However, be certainthat all student divers demonstrate mas-tery on required performances. Whennecessary for logistics or due to classsize, staff members may function as team members.

3. Note that the Trimix Diver Exam follows Practical Application Four.This is to allow students to apply their knowledge for better under-standing and application prior to being tested on it.

D. The Training Dives appear in the outline sequenced amid prerequi-site Knowledge Development and Practical Application.1. The standards for each dive vary in terms of depths, ratios, etc. as

well as performance requirements. See the outline for each dive forthe individual dive standards.

2. Training Dives have several goals in the Tec Trimix Diver course:a. To refresh and refine prerequisite skills, procedures and equip-

ment configuration in preparation for the more precise divingdemanded by helium gases.

b. To allow student divers to transfer what they learn duringKnowledge Development and Practical Application to actual divecircumstances.

c. To allow knowledge and skills to integrate into a unified set ofmotor skills and procedures for dive preparation, dive planning,making the dive, handling dive problems and creating solutionsduring the dive.

d. To allow students to demonstrate their performances for you soyou can assist development and assess mastery.

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3. The dives in the Tec Trimix Diver course are sequenced for instructionalprogression:a. Initial dives review prerequisite knowledge and skills and introduce

new knowledge and skills as individual tasks.

b. The next dives integrate the new and old knowledge and skills duringsimulated trimix dives. Students practice and apply skills in context.

c. The final dives are actual trimix dives duringwhich students primarily demonstrate mastery.

III. Knowledge Development Presentation OneA. Introductions [Encourage a relaxed atmosphere and

begin interaction that will be the basis for teamwork.]1. [Introduce yourself, staff and anyone else involved in the course.

Provide a bit of your background, including some things that don’tinvolve diving. Have your staff do the same.]

2. [Have students introduce themselves. Ask them to tell everyone howthey got into tec diving, and then one thing about themselves not relat-ed to diving that everyone probably wouldn’t know. This is usually agood ice breaker.]

3. [Collect Knowledge Reviews from Section One of the DSAT Tec Trimix

Diver Manual. For students who’ve qualified for the course with a pre-requisite certification other than DSAT Tec Deep Diver, collect all theKnowledge Reviews from the Tec Deep Diver Manual as well. You’llreview the Knowledge Reviews to assess mastery and tailor your subse-quent presentation accordingly. You can do this during a break or whilestudents complete paperwork, etc.]

B. Course Goals and Your Responsibilities1. The goals of the Tec Trimix Diver course are:

a. To qualify you to plan and make dives with open cir-cuit scuba using various trimix blends, air, enrichedair and oxygen, using the technical diving equip-ment and procedures required to manage therisks involved.

b. To train you in the cognitive and motor skillsrequired for technical trimix diving.

c. To assure you acknowledge and understandthe hazards and risks of technical diving ingeneral and trimix diving in particular, aswell as the limits of training received in the course.

d. To train you to prepare for and respond to reasonably foresee-able emergencies that may occur in this type of technical diving.

e. To provide skills applicable to further training and experience in technical diving.

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39

Chapter ONE

Knowledge Review –Chapter OnePlease complete this review, and remove it from the manual to hand in to your instructor. If there’s

something you don’t understand, review the related material. If you still don’t understand, be sure

to have your instructor explain it to you.

1. Is a gas blend of 19 percent oxygen, 33 percent helium and 48 percent nitrogen a

trimix? If so, is it a normoxic trimix, and how would you write the abbreviation for it?

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

2. What are three benefits and three drawbacks of diving with trimix?

Benefits1. ________________________________________________________________

2. ________________________________________________________________

3. ________________________________________________________________

Drawbacks1. ________________________________________________________________

2. ________________________________________________________________

3. ________________________________________________________________

3. Below what depth is trimix the broad community standard for all diving? Below

what depth for overhead environments or complex environments? To what depth is

the typical range for new, beginning trimix divers, assuming experience at that

depth during training?__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

4. Trimix can be made several ways. Describe how trimix is made by partial pressure

blending with enriched air.

__________________________________________________________________

__________________________________________________________________

ON

EY e s i t i s t r i m i x . I t i s n o t n o r m o x i c t r i m i x .

Y o u w o u l d a b b r e v i a t e i t T M x 1 9 / 3 3 .R e d u c e d n a r c o s i s

R e d u c e d o x y g e n e x p o s u r e

R e d u c e d b r e a t h i n g r e s i s t a n c e

E x p e n s eL o n g e r D e c o t i m e s

M o r e c o m p l e x l o g i s t i c s a n d p l a n n i n gB e l o w 1 6 5 f e e t t r i m i x i s t h e b r o a d c o m m u n i t y

s t a n d a r d f o r a l l d i v i n g .

B e l o w 1 3 0 f e e t f o r o v e r h e a d o r c o m p l e x e n v i r o n m e n t s .

T o 2 4 5 f e e t i s t h e r a n g e f o r n e w , b e g i n n i n g t r i m i x

d i v e r s .

T h e b l e n d e r a d d s p r e m i x e d e n r i c h e d a i r t o a

c y l i n d e r w i t h h e l i u m t o p r o d u c e t h e d e s i r e d t r i m i x .

[This section address the Tec Trimix Diverstudent. Notes to the

instructor appear in brackets.]


2. While taking the Tec Trimix Diver course, you have these obligationsand responsibilities:a. Follow the instructor’s directions and dive plans strictly, and to not

separate from the instructor or your dive team.

b. To maintain adequate physical and mental health, and to alert theinstructor to any problems you have with either.

c. To accept the risk of technical and trimix diving, and for specificrisks unique to each dive environment, and to immediately notifythe instructor if this risk becomes unacceptable to you.

3. Failing to meet these obligations and responsibilities can have theseconsequences:a. In the worst case, you can be seriously injured, disabled or killed.

b. You will have failed to demonstrate the attitude and matu-rity required for tec diving, and will not qualify for certifi-cation.

C. Course Overview, Logistics and Administration1. Schedule [Explain anything that you have not previously

covered with respect to course scheduling, includingstudy assignments and due dates, sessions and trainingdives. It’s recommended you have these printed outand go over them with students when they enroll inthe course.]

2. Students sign the Tec Trimix Diver Statement ofUnderstanding and Learning Agreement. [Discusswhat the agreement doesn’t cover, such as your poli-cies regarding make ups for missed assignments or dives, etc.]

3. Certificationa. Upon successfully completing all course requirements, you’ll

receive the DSAT Tec Trimix Diver certification.

b. Certification as a DSAT Tec Trimix Diver will mean that you’re quali-fied to:

• Plan and make decompression stop dives using trimix as a bot-tom gas and trimix, enriched air and oxygen as decompressiongases within the limits of your training and experience.

• Purchase trimix and purchase/rent equipment required for divingwith trimix.

c. Certification as a DSAT Tec Trimix Diver also means that youassume all the risks and consequences of technical diving, trimixdiving and diving in general.

4. Class Requirementsa. Course costs [Explain all costs associated with the course. Collect

outstanding funds due as appropriate, explain refund policies, etc.]

b. Equipment and material requirements [Explain what’s required forthe course, and of that, what students must provide and what youwill provide.]

padi.com 3-5

Tec Diver Statement of Understanding

and Learning Agreement

This statement informs you of hazards, risks and your responsibilities for participating in the DSAT Tec Diver

course. Your signature acknowledges that you accept these risks and responsibilities.

I, ___________________________________________________, understand that as a DSAT Tec Diver I should:

1. Maintain good mental and physical health for diving.

Refrain from being under the influence of alcohol or

drugs when tec diving. Stay proficient in diving

skills, in particular, the skills required for certifica-

tion as a DSAT Tec Diver.

2. Engage only in diving activities consistent with my

training and experience.

3. Use complete, well-maintained, reliable equipment

for which I have appropriate training.

4. Adhere to the team diving concept, but always be

prepared to complete any dive without the assis-

tance of a team mate. Although self sufficient, the

responsible tec diver dives as part of a team and

adheres to team diving principles.

5. Maintain the proper attitude during training in which

I agree to:• Follow the instructor’s directions and dive plans

strictly, and not to separate from the instructor or

my dive team.• Refrain from tec diving outside this course until I am

fully qualified and certified.

• Accept the risk for this type of diving, and for spe-

cific risks unique to each dive environment, and to

immediately notify the instructor if this risk

becomes intolerable for me.

• Recognize the desirability of carrying diver accident

insurance that covers tec diving (if available in my

local area), and recognize that my instructor may

require me to have it.

6. Demonstrate self sufficiency – plan each dive as

though it will be necessary to make the dive and

handle all emergencies alone.

7. Demonstrate discipline and an attitude consistent

with responsible technical diving – I will not cut cor-

ners, bend the rules, disregard dive plans, omit safe-

ty equipment or exceed the limits of my training.

8. Obtain an orientation when diving in new environ-

ments.9. Know, obey and respect local diving laws and regula-

tions including private land owner relations.

10. Accept the responsibility for my personal safety,

while accepting and acknowledging the risks, and

demands tec diving imposes.

11. Stay informed on and dive according to the state

of the art in diving, tec diving, dive rescue, dive

equipment and other influences on my safety as a

tec diver.12. Accept that technical scuba diving has many gen-

eral risks and hazards that either don’t exist in

recreational diving, or aren’t as severe, including:

• No direct access to the surface in an emergency

due to decompression requirements.

• Hypoxia/hyperoxia resulting from switching to the

wrong gas, which can lead to drowning.

• Narcosis, which can lead to poor judgment/bad

decisions that can cause an accident.

• DCS due to improper gas analysis, missed deco

stops, loss of deco gas and individual susceptibili-

ty. DCS can cause permanent injury or death.

• Omitted procedures due to task loading, which

can lead to accidents, DCS, air embolism, oxygen

toxicity, or drowning.

• Drowning or air embolism due to BCD failure.

• Extensive equipment requirements with redundant

configurations, which can lead to ergonomic com-

plexity, increased risk of error and a physical bur-

den.13. I accept that a significant difference exists between

recreational scuba diving and technical scuba div-

ing, and that in technical scuba diving, even if you

do everything right, there is still a higher inherent

potential for an accident leading to permanent

injury or death.14. I accept that physical fitness affects my perform-

ance and ability as a tec diver. Lack of the physical

fitness required can affect my safety by limiting my

ability to respond to an emergency, or by directly

leading to injuries. It is my responsibility to stay fit

to dive, and to dive with the limits of my fitness.

I have read the above statements and have had any questions answered to my satisfaction. I understand the impor-

tance and purpose of these practices and recognize they are for my own safety and well being.

I understand that failing to ahere to the above statements will put me at risk, and may be grounds for my dismissal

from the Tec Deep Diver course. I acknowledge that the instructor is not permitted to and will not certify me if I

don’t meet all course performance requirements or if I demonstrate an attitude or behavior incompatible with

responsible technical diving practices.

__________________________________________________ ___________________________

Participant Signature

Day/Month/Year

padi.comG Product No. 10267 Version 1.0 (07/03)



c. Course prerequisites [Confirm the prerequisites in Section Two ifthese were not handled during course registration or as otherwisenecessary.]

d. If you’ve qualified to participate in the Tec Trimix Diver coursethrough a qualifying certification other than the DSAT Tec DeepDiver certification, you must read the entire Tec Deep Diver

Manual and complete the Knowledge Reviews prior to beginningthe Tec Trimix Diver course. [This isn’t required if the Tec Deep

Diver Manual isn’t available in a language the student can understand,but the student must still complete the Knowledge Reviews, receivingremedial instruction as necessary.]

5. Administrationa. [Have student divers read, complete and sign the Liability Release

and Express Assumption of Risk for Technical Diving (or the techni-cal diving release specified by your PADI Office for your localarea). The release must be signed before any inwater training.

b. Prior to any inwater training the student must have physician’sapproval and signature on the Medical Statement, even if the stu-dent answered “no” to all medical conditions listed on the form. Ifthe student received a physician’s approval and signature on aMedical Statement for another course in the last year and has hadno medical condition change, and if you have that MedicalStatement on file, then the student does not need to see a physicianagain.

c. Diver insurance [It’s recommended that you require students in theDSAT Tec Trimix Diver course to have diver insurance such as thePADI Diver Protection Program, Platinum or equivalent as available inyour area.]

D. Trimix Diving Risks

Learning Objectives: By the end of this section, you should be able

to answer these questions:

1. What ten risks and hazards does technical diving with trimix

present that either don’t exist or aren’t as severe in recreational

diving and air/enriched air technical diving?

2. What are the limits of your training as a Tec Trimix Diver?

3. What risks do you face if you exceed these limits?

4. How do you responsibly extend your limits with trimix diving?

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[Note: This is a good place for a break prior to getting intothe actual course material.]


1. In the Tec Deep Diver course, you learned risks and hazards that tecdiving presents that either don’t exist or aren’t as severe in recreationaldiving. There are also risks specific to diving with trimix.a. Helium differs from nitrogen in its properties. It is less forgiving of

some procedural errors, such ascending above stop depth. Anecdotalsources indicate a slightly higher DCS rate for diving with helium; thisis currently debated and unclear, but nonetheless a risk you mustaccept.

b. More risk of the unknown than air/enriched air diving. There’s agrowing field experience, but every trimix dive is somewhat experi-mental because there’s been little formal testing of it, and thereforemore unknown risk.

c. If you deplete, lose or have a failure in your decompression gases,you’re unlikely to be able to decompress adequately with your bottom trimix.

d. Gas blend inaccuracy leading to DCS due todecompression calculation error. Traditionally,trimix is analyzed based on the oxygen compo-nent; blending procedures must be followedcarefully to assure an accurate blend. Not awidespread problem, but the risk is present.(Note: The recent introduction of helium ana-lyzers reduces this concern.)

e. Vestibular DCS (inner ear DCS) is rare, but most commonly associat-ed with deep dives using helium. Usually occurs with dive depthsdeeper than typical trimix diving, but the risk is there. Can alsooccur, but even more rarely, with air/enriched air.

f. Hypothermia – primarily a risk if forced to use trimix in your dry suitbecause helium carries away heat (more about this later); longerdeco times are also an issue, especially if your suit leaks.

g. Hypoxia – deeper dives using trimix may require using bottom mixesthat have too little oxygen at the surface. Breathing such a mix at thesurface or too shallow can cause unconsciousness, followed bydrowning, without warning.

h. Hyperoxia – Due to depth and gases, trimix deco times tend to belonger than air/enriched air diving with higher oxygen exposure, pos-ing more risk of CNS and/or pulmonary oxygen toxicity. Middle earoxygen exposure during and following decompression can cause amiddle ear squeeze (prevented by being aware and gently equalizingperiodically, even when remaining at a constant depth).

i. Isobaric counterdiffusion – DCS caused by switching to a light gas fol-lowing breathing a heavy gas. The risk also involves potentiallysevere skin DCS from using trimix in your dry suit. (More about thislater.)

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j. Difficult or impossible to be rescued – deeper dives and longerdecompressions common to trimix diving greatly complicateattempts to rescue a diver. In some circumstances, team mates oryour instructor may not be able to even attempt a rescue withoutunreasonable risk of personal harm, due to low gas or decompres-sion requirements. This is a risk you must accept both in thiscourse and after as a certified trimix diver.

2. Limits of Tec Trimix Diver traininga. The Tec Trimix Diver certification qualifies you to initially dive to a

maximum of 75 metres/245 feet or the maximum depth at which youtrained (whichever is shallower) using open circuit technical divingequipment with trimix as a bottom gas, and trimix, enriched air andoxygen for decompression.

b. Stay within the limits of your experience and training. Initial divesafter certification should be well within these. Plan simple dives togain experience.

c. Extending your limits responsibly with trimix (depth, duration, com-plexity) requires many dives. Build experience gradually and conser-vatively. Dive with more experienced teammates.

d. Failure to stay within the limits of your training and experienceposes risk of permanent injury or death to you and/or teammates!

E. Introduction to Trimix Diving



1. What is trimix?

2. What is the nomenclature for identifying a trimix?

3. What is meant by “normoxic” trimix?

4. What are three benefits of diving with trimix?

5. What are three general drawbacks of diving with trimix?

6. What are the generally accepted ranges for trimix?

7. How is trimix made?

8. How do you analyze trimix?

1. Trimix is a blend of oxygen, helium and nitrogenused for deep technical diving.a. Nomenclature: “Trimix” followed by the num-

ber for the oxygen percentage, then the heliumpercentage. Abbreviated “TMx”

b. E.g. TMx 18/50 = 18 percent oxygen, 50 percenthelium, balance nitrogen

c. Trimix with 21 percent oxygen is called “normoxic” trimix because ithas the same (normal) oxygen fraction as air does.

d. Trimix has also been made with gases other than helium (e.g. neon),but for this course and your qualification, trimix is oxygen, heliumand nitrogen.

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e. Fractions of helium and oxygen vary depending on dive require-ments. You’ll learn about determining these as part of this course.

2. Benefits of diving with trimix: these are the three primary reasonsdivers use trimix for deep diving.a. Reduced narcosis (helium is non narcotic).

b. Reduced oxygen toxicity (gas blended to have less than 21 percentoxygen when going deeper than 55 metres/185 feet).

c. Less dense for reduced breathing resistance at depth.

3. General drawbacks of diving with trimix: In addition to risks listed ear-lier, trimix has a few drawbacks.a. Expense. Trimix costs considerably more than air and enriched air

because helium costs more.

b. Longer decompression times. For the depths and durationsinvolved in tec diving, trimix dives typically require longer decom-pression than the same dive with air/enriched air nitrox.

c. More complex logistics and planning. Diving with trimix may havemore complexity, require more hardware, planning and preparation.

4. There are differing opinions as to how deep you can go before trimix isconsidered required. Broadly:a. Air/enriched air are considered acceptable for open water diving,

with a simple dive objective and in good conditions to 50 metres/165 feet.

b. Below 40 metres/130 feet, trimix is the broad community standardfor overhead environments or complex objectives. The more chal-lenging the environment, the more appropriate it is to use trimix.[Note: Some divers apply these guidelinesbeginning at 30 metres/100 feet.]

c. Below 50 metres/165 feet, trimix is consideredthe broad community standard for all diving.[Note: Some dive communities acceptair/enriched air diving to 55 metres/185 feet inoptimum, open water conditions.]

d. The maximum depth for trimix has yet to befully established.

• Typical range for new, beginning trimixdivers is to 75 metres/245 feet, or the maxi-mum depth experienced during training.

• Experienced trimix divers sometimes usetrimix as deep 90 metres/300 feet.

• Dives between 90 metres/300 feet and 120 metres/400 feet are not unusual for veryexperienced trimix divers.

• The maximum depth for this course is 75 metres/245 feet.

padi.com 3-9


• Qualifying to dive deeper requires time and experience. You’lllearn more about this later.

5. Trimix Blending

a. Trimix is made by blending helium, air/enriched air and/or oxygen.

b. Partial pressure blending: Based on the required mix, blender addsrequired helium, oxygen and air in steps to a cylinder. [Demonstrateblender software if available.] Oxygen is analyzed at each step tocontrol final blend.

c. Partial pressure blending with enriched air: Blender mixes premixedenriched air nitrox with helium in cylinder.

d. Membrane blending/continuous flow with partial pressure: Blenderfills cylinders with required helium, then tops to full pressure withEANx required for final blend from membrane or continuous flowsource.

e. Continuous flow with helium, oxygen and air: Gases flow into mixchamber in the right proportion, then into compressor for pumpinginto cylinders. Requires helium analyzer as well as oxygen analyzer.

6. Analyzing trimixa. You analyze trimix using an oxygen analyzer the same

way you analyze enriched air nitrox.

b. The blender analyzes oxygen at each stage whenblending after allowing adequate time for gases tomix. If each step has the correct oxygen, the final blend can bedetermined accurate by oxygen analysis alone.

c. If oxygen is off by more than one percent, adjust your dive comput-er or dive tables accordingly, or have the cylinders reblended withthe correct mix.

d. Helium analyzers are expensive but available. If available, you use itin addition to the oxygen analyzer. You always analyze the oxygencontent of every cylinder you will use.

• Note that without a helium analyzer, you must know

what the target blend was to analyze the final mix.

• Blending trimix in cylinders partially filled withtrimix (to save helium) tends to compound minor blending errorsunless you have a helium analyzer.

• This is why the practice without a helium analyzer is to complete-ly drain trimix cylinders and blend in empty cylinders when usingonly an oxygen analyzer is available. (Depending on mix gasesavailable, a single “top up” is sometimes considered acceptable.)

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[Note: This is a brief overview. If student divers havequalified as trimix gas blenders and have already completed their training, you may omit this topic.]

[Note: Demonstratewith trimix usingstandard oxygen analyzer.]

[Note: If available,demonstrate use ofhelium analyzer.]


e. You’ll practice analyzing trimix beginning in Practical ApplicationTwo.

F. Equipment I – Rigged for Trimix Diving



1. Why might you carry more than two stage/deco cylinders on a

trimix dive?

2. What are the proper markings on trimix cylinders?

3. What are the two ways you can carry four stage/deco cylinders?

4. Why can’t you inflate your dry suit from your back gas when

trimix diving?

5. Why would you put a low pressure inflator hose on a decom-

pression cylinder containing air or enriched air nitrox?

6. How do you set up an independent inflation system, and where

do you typically put it?

7. What is the advantage of using argon as a dry suit inflation gas?

1. The standardized technical rig – you’ll be diving with the equipmentconfiguration you learned in the Tec Deep Diver course, which is theemerging general community standard for deep tec diving.[Note: Refer students to the Tec Deep Diver Manual for details.]a. Note that due to depth and rapid gas consumption, trimix dives

tend to be made with high capacity double cylinders.

b. Due to weight of all cylinders, as well as gas weight in high capacitycylinders, redundant buoyancy control is essential. If a dry suitwould not provide adequate backup buoyancy or if using a wet suit,then twin bladder BCD is required.

• using a wet suit with steel stage/deco cylin-ders makes a twin bladder BCD essential dueto significant negative buoyancy

• some divers have a low pressure inflatorhose on one of their stage/deco cylindersthat they can attach to a BCD inflator shouldthey exhaust their back gas in an emergency(as discussed later, it can also be used on adry suit)

2. Stage/decompression cylindersa. As a Tec Deep Diver, you’ve learned to carry

two stage/deco cylinders

• two cylinders usually more than adequate for volume and rangeof air/enriched air decompression and extended no stop diving,and for many trimix dives

b. As a Tec Trimix Diver, you may be diving with more than twostage/deco cylinders.

• Trimix dives tend to be deeper, requiring larger deco gas volumes.

padi.com 3-11


• On longer, deeper dives, three or four different deco gases may benecessary to supply the required volumes, and may reduce decotime by optimizing the fraction of oxygen.

• Some trimix blends may have very low oxygen content and not besuitable for breathing at shallow depths – you may need a travel

gas – a higher oxygen content deco/stage gas you use until reach-ing the appropriate depth for your back gas.

• More than two deco cylinders is more typical after you gain expe-rience, and more common in some environments, like cave diving,than in others.

c. Wearing four stage/deco cylinders

• May be worn all left or right and left, as with two cylinders.

• Essential to have a personal standard: wear cylinders the sameway all the time, with same cylinders in same place.

• All left – Common to stack two and trailtwo by top hook on hip D-ring.

• Right/left – typical to stack two eachside, or wear one each side and trailother two (one side or both) by tophook on hip D-ring.

• At times, it’s useful to hook only topclip to shoulder D-ring, esp. if you’llshortly move the cylinder to trail bytop clip on hip D-ring.

• You’ll practice handling up to fourcylinders. However, the majority ofintermediate depth trimix dives generally require only two decogases. Remember to simplify your rig and logistics as much aspossible. If two will do the job, use two.

d. Deco cylinder types

• Because they’re light and easy to handle underwater, many diversprefer the “aluminum 80” (11 litre) as the optimum typestage/deco cylinder, especially for trimix dives that require morethan two deco cylinders and for all left configuration.

• Using aluminum 80s, it’s quite feasible to handle four or morestage/deco cylinders, though drag is still an issue, especially ifyou must wear them the entire dive.

• Aluminum 80s or cylinders with comparable buoyancy character-istics are required for all left configuration.

• In some local areas, only steel cylinders or other substantiallynegative cylinders are readily available; in these areas, using onlytwo deco gases is the standard practice, even with trimix.

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3. Trimix markingsa. Cylinders with trimix are clearly marked with a label that says

“Trimix.” Color coding for trimix isn’t standardized like enriched airand oxygen, and the practices may vary.

• Essential to clearly identify “Trimix” in all cases.

• Cylinders should be kept isolated so that they cannot be usedaccidentally by unqualified divers.

b. Cylinders also marked with analyzed content, maximum depth anddiver’s name, all visible to teammates when worn.

c. In some locations, formal tank cylinder labels/tape are common forthis purpose. In other dive communities, divers simply write theinformation on gray (duct) tape; and yet other communities maycombine these practices.

d. The essential point is that to avoid accidents caused by confusinggases, all cylinders need proper markings in accord with local prac-tices.

4. Argon inflation systemsa. Because helium conducts heat rapidly, you can’t use trimix in your

dry suit. Helium in the dry suit also poses a DCS risk due to isobariccounterdiffusion (more about this in later sections), so an alterna-tive inflation system is used.

b. If diving in a dry suit, you use a small separate inflation cylinder,typically mounted on the left doubles cylinder, valve down foraccess while worn and to reduce entanglement hazard. LP hoserouted under harness to eliminate slack. (A few divers wear onright, depending on dry suit valve orientation.)

c. Argon is preferred inflation gas because it insulates better than airand has little risk of isobaric counterdiffusion. No second stage onregulator so it cannot be breathed accidentally; regulator shouldhave overpressure relief valve. Cylinder clearly marked with argondecal.

• One reported study found no difference in the insulating qualitiesbetween argon and air, though divers widely report a difference.

d. Some trimix divers also have a LP hose on an air or enriched airdeco cylinder in case they exhaust or have a problem with theargon system.

padi.com 3-13

[Note: The next section reviews techniques learned in the TecDeep Diver course. Remind student divers that they will be practic-ing and demonstrating the skills they learned in the Tec Deep Divercourse during the Training Dives. Refer them to the DSAT Tec Deep

Diver Manual for skill descriptions and reminders.]


G. Techniques and Procedures I



1. What is the general recommendation regarding how deep you

take a cylinder, and what is the issue in trimix diving with

regard to this recommendation?

2. What are the procedures for gas switches with up to four deco

cylinders?

3. How precise should a decompression stop be?

1. Gas switchesa. During the Tec Deep Diver course, you learned that switching to the

wrong gas is one of the most common causes of tec diver deaths.

b. You learned to use the NO TOX mnemonic toremember the steps for a proper gas switch in thecorrect order. [Refer students to the Tec Deep Diver

Manual and the TecRec Equipment Setup and Key

Skills video for details.]

c. When switching to or from trimix, you can confirmthat you’ve gone on or off of trimix by speaking intoyour regulator and listening for helium distortion.

2. Remember, the general recommendation is to nevertake a cylinder deeper than you can safely breathefrom it (maximum depth). a. This isn’t feasible in many open water environments

due to concerns about relocating the cylinders. (It’sessential that you be able to relocate them.)

b. If you can follow this guideline without serious risk of losing thecylinders, it minimizes the probability of switching to the wrong gas.

c. The issue with this recommendation in trimix diving is that you’rehighly unlikely to be able to adequately decompress without yourdeco cylinders. Therefore, the priority is to not risk losing them.

3. Handling three or four cylinders worn on both sides.a. Traditional to wear oxygen and next highest oxygen deco on right,

lowest oxygen/travel gas left (remember Right – Rich, Left – Lean).You’ll learn more about travel gas later.

b. Several handling options popular:

• Stacking all four, two per side: breathe top left, bottom left, topright, bottom right (common to move top cylinders back to trailon hip D-ring after use).

• Wearing two and trailing two: breathe worn left, switch withtrailed left and breathe, breathe worn right, switch with andbreathe trailed right.

• IMPORTANT: Be consistent, always use the same arrangement andalways follow the NO TOX switch procedure.

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4. Handling three or four cylinders worn all on left side.a. Most common to wear two and trail two.

b. The cylinder you’re breathing is always on top.

c. Move cylinders as you switch.

d. Preplanning reduces moves.

• If staging cylinders at deepest depth you can breathe them: wearlowest and second lowest oxygen (lowest may be deco or travelgas), trail oxygen and highest oxygen to easily stage. You switchas you retrieve, shifting used cylinder to trail and wearing cylin-der you’re breathing.

• If not staging (wearing whole dive), one option is to wear lowestand second lowest oxygen cylinders with the lowest (first used)on top, and trail other two. When through with the bottle on top,trail it and switch. After switching, bring up next gas to be usedunder the cylinder in use (one in use is always on top).

• If not staging (wearing whole dive) some divers prefer to wearonly lowest oxygen cylinder (first used) with all others trailed.Switch to trailed cylinders in order.

• IMPORTANT: Be consistent and follow NO TOX procedure onevery gas switch.

e. Remember that carrying only two cylinders simplifies handling andprocedures. If you only need two cylinders to provide adequate gassupply with reserve, there’s no reason to use three or four.Especially as a new trimix diver, the majority of your dives will onlyrequire two.

5. In both all left and left/right configuration, top hooking to chest D-ringallows you to wear two and breathe from a third (top hooked) if you’llnot be using it long. Commonly used with travel gas that will be stagedshortly, and/or using travel gas briefly until switching to a higher oxy-gen deco gas.

6. Decompression stopsa. In the Tec Deep Diver course, you learned that precision is essential

when making decompression stops.

b. As you’ll see, this is particularly important when diving with trimix.Because it diffuses rapidly, helium is less tolerant of poor depthmanagement during decompression.

c. You’ll practice making precision deco stops using buoyancy controlfor extended periods, with and without a visual reference. You mustvary no more than .6 metres/2 feet from the stop depth.

• aim for no more than half that variation

• requires constant attention when you don’t have a physical contact

• must pay attention to gas, times and teammates at same time

d. Think of the surface as a deco stop. Before immediately exerting

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yourself by swimming, climbing, etc., whenever possible rest for fiveto ten minutes first. Continue breathing high oxygen deco gas.

H. Emergency Procedures I


to answer this question:

1. Where can you find descriptions of skills for review?

1. During the course, you’ll be practicing skills you mastered in the TecDeep Diver course and applying them to the higher complexity of trim-ix diving.

2. You should be prepared to practice the following skills during thetraining dives:a. gas sharing with long hose, swimming and stationary, with and with-

out mask

b. valve shut down drill

c. unconscious diver

d. lift bag deployment

3. You can find descriptions of these skills in the Tec Deep Diver Manual ifyou want to review them. You can also see them in TecRec Equipment

Setup and Key Skills video.I. Decompression I



1. What are the five reasons that the use of desktop decompres-

sion software is standard practice in trimix diving?

2. What are the two main differences between desktop decompres-

sion software for air/enriched air/oxygen and for trimix?

3. What are the two basic categories of decompression models

found in desktop decompression software?

4. What are the basic attributes of each of the two categories of

decompression models?

1. The trend in tec diving is to use desktop decompression software,along with multigas dive computers, to plan and make dives.a. This approach maximizes adaptability to specifics of situation

b. Desktop decompression software allows plans based on known realprofiles rather than square profiles – especially beneficial incaves/wrecks or following topography.

c. Divers may increase the conservatism as appropriate for their indi-vidual circumstances and risk tolerance.

d. Desktop decompression software more accurately reflects what amultigas computer will allow, making it more suitable for planningmultigas computer dives and backup tables for multigas computerdives.

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2. Virtually all trimix divers use desk-top decompression softwarea. Theoretically, there are hundreds

of possible trimix blends.Software lets you write a table forwhat you’re actually using ratherthan for a range of possibleblends.

b. Desktop deco software simplifiesgas use calculations and simpli-fies dive planning by allowingyou to quickly compare differentpossible profiles, including using different gases and gas switchdepths.

c. Software allows you to add deep stops or use trimixes for decom-pression; this isn’t as straightforward with preprinted tables.

d. Software easily generates contingency tables for the dive, includingtables for more or less depth/time combinations, and for decom-pressing without deco gases (if possible).

e. Even using a multigas trimix computer you need desktop deco soft-ware for dive planning and generating backup tables, etc.

• You don’t dive multigas computers blindly – you need to knowwhat to expect ahead of time.

• The generated tables may prove more efficent, logisitically feasi-ble or have a more readily applicable deco schedule than thecomputer.

• At this writing, desktop software allows more user choice andmodel sophisitication than most multigas trimix computers –though this may change with time.

f. Do not use tables for military or commercial divers. The tec com-munity consensus is that these are not appropriately designed fortec divers and tec diving purposes. The potential risk appears to behigher, which may be appropriate for commercial and militarydivers with unlimited gas supply and recompression on site, but isnot for tec divers.

3. The main differences between desktop decompression software forair/enriched air/oxygen diving and trimix diving are the ability toselect trimix in the gas choices, and deeper maximum depth calcula-tions allowed.a. The software you already have can probably be upgraded to trimix

either online or over the telephone.

b. You may have options in different versions of trimix software (seemanufacturer of specific software).

4. Decompression models used in desktop decompression software

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a. Most common decompression models (a.k.a. algorithms) are neo-Haldanean – models based on Haldanean dissolved gas concepts.

• assumes no bubbles form – an assumption we know isn’t entirelycorrect

• deco strategy is to get the diver to the shallowest allowable depthfor shortest decompression (the shallower the diver, the morerapidly gases dissolve out of the tissue)

b. Of these, variations of the Buhlmann model are most common

• widely used in dive computers

• conservative

• versatile – easily modified for different applications

• has a large base of successful testing and field use

c. Some desktop decompression software now uses bubble dynamicsmodels.

• assumes some subclinical bubbles form, and growth of these bub-bles, if not controlled, causes DCS

• deco strategy is to emphasize deeper and more frequent stops tominimize bubble formation for shortest decompression (oncebubbles form, they take longer to eliminate than dissolved gas)

• characterized by predicting shorter deco times than mostBuhlmann models, but also shorter no stop times

• lacks same level of testing and field experience, but nothing atthis writing has suggested that such models aren’t reliable

• basis for deep stops procedure that has become the norm regard-less of deco model being applied (more about this later)

d. Desktop deco software and multiple gas trimix computers offerusers the choice of Buhlmann models or bubble models (ReducedGradient Bubble Model [RGBM], Varying Permeability Model [VPM],etc.); some versions offer a choice within the same software or divecomputer.

J. Gas Planning I


to answer this question:

1. What are the two ways you’ll determine the gas volumes you

require, including reserves, for a trimix dive?


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[Note: This guide and program reference “ata” (atmospheres) asthe unit of pressure that’s used most commonly by the dive com-munity when referencing partial pressures. Although not preciselythe same as the metric bar, for practical purposes within thescope of this program they may be considered interchangeable.]


1. Gas volume, oxygen exposure planninga. You determine your gas volumes and reserves based on your

planned dive schedule and SAC rate, just as you learned in the TecDeep Diver course, with a few differences.

• Oxygen exposure limits and emergency procedures are exactlythe same as you’ve already learned for air/enriched air diving.

• Use Trimix Oxygen Management Tables for determining trimixPO2s, CNS percent and OTUs.

• Use Equivalent Air Depth and Oxygen Management Tables (seethe Tec Deep Diver Manual appendix) for determining PO2s, CNSpercent, OTUs and EADs for EANx and oxygen.

• Trimix schedules commonly have multiple deep stops more than3 metres/10 feet apart. Calculate ascents between these untilreaching stops separated by 3 metres/10 feet. At that point, usethe add-one-minute-every-third-stop method.

• Be aware that effective breathing habits have more effect on trimix diving due to the depth. Deviations from normal breathingrhythms can affect your gas plan substantially. Get in the habit ofslow, deep breathing that maximizes gas exchange in the lungs.Avoid the tendency to breathe shallow and fastwhen under stress and working hard – stop whatyou’re doing and reestablish slow, deep breathing.

b. You calculate your oxygen exposure following theseguidelines as well.

c. Desktop decompression software also calculatesthese, though you need to determine your SAC bot-tom (working) rate and deco rates to get accuratevolume calculations.

2. To be successful in the Tec Trimix Diver course, you willneed to be able to determine volumes, SAC, oxygenexposure, reserves and maximum depths (based on oxy-gen) much as you learned in the Tec Deep Diver course.a. Tec Trimix Diver course will emphasize using desktop

deco software for this, but you will also plan a fewdives manually, including on the exam.

• Manually determining these may be necessary ifyou have deco schedules available in the field, butno desktop deco software to calculate your personal gas con-sumption, etc.

b. If necessary, you can find the material on these for review and torework problems in the Tec Deep Diver Manual. [Note: You maywish to work the following sample gas planning problem to reviewthis with students. This sample uses trimix to show that there’s nodifference using it in these aspects of planning.]

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Depth (m) Conversion Depth (ft) ConversionFactor Factor

3 1.3 10 1.3

5 1.5 15 1.5

6 1.6 20 1.6

9 1.9 30 1.9

12 2.2 40 2.2

15 2.5 50 2.5

18 2.8 60 2.8

21 3.1 70 3.1

24 3.4 80 3.4

27 3.7 90 3.7

30 4.0 100 4.0

33 4.3 110 4.3

36 4.6 120 4.6

39 4.9 130 4.9

42 5.2 140 5.2

45 5.5 150 5.5

48 5.8 160 5.8

51 6.1 170 6.2

54 6.4 180 6.5

57 6.7 190 6.8

60 7.0 200 7.1

63 7.3 210 7.4

66 7.6 220 7.7

69 7.9 230 8.0

72 8.2 240 8.3

75 8.5 250 8.6

78 8.8 260 8.9

81 9.1 270 9.2

84 9.4 280 9.5

87 9.7 290 9.8

90 10.0 300 10.1

METRIC IMPERIAL

TRIMIX SAC CONVERSION FACTORS

Multiply your SAC rate by the factor to determine your gas comsumption rate at depth.


METRIC

Example: You’re planning to dive to 55 metres for 20 minutes using TMx 21/35. Your decom-pression schedule, which has the deep stops precalculated, calls for a 10 mpm ascent rate,with a one minute stop at 33 metres using EANx36, followed by one minute at 21 metres, oneminute at 18 metres, one minute at 15 metres, two minutes at 12 metres and five minutes atnine metres with EANx50. The final stops use pure oxygen for two minutes at six metres and17 minutes at five metres. Your SAC rate is 19 litres per minute for the working part of thedive and 16 lpm when decompressing. Assuming a one third reserve, determine your gas volume requirements, OTUs and CNS clock using the appropriate tables.

Dpth Tme SAC CnFct Vol. Gas PO2 OTU OTUs CNS/ CNS%mins min

55 20 19 6.7 2546 TMx21/35 1.41 1.64 32.8 .83 16.6%

44 (a) 2 19 5.5 209 TMx21/35 1.16 1.25 2.5 .48 .96%

33 1 16 4.3 69 EANx36 1.55 1.85 1.85 2.22 2.22%

27 (a) 1 19 3.7 70 EANx36 1.33 1.53 1.53 .67 .67%

21 1 16 3.1 50 EANx50 1.55 1.85 1.85 2.22 2.22%

18 1 16 2.8 45 EANx50 1.4 1.63 1.63 .67 .67%

15 1+1 16 2.5 80 EANx50 1.25 1.4 2.8 .55 1.1%

12 2 16 2.2 70 EANx50 1.1 1.16 2.32 .42 .84%

9 5 16 1.9 152 EANx50 .95 .92 4.6 .33 1.65%

6 2+1 16 1.6 77 oxygen 1.6 1.92 5.76 2.22 6.6%

5 17 16 1.5 408 oxygen 1.5 1.78 30.26 .83 14.11%

TMx21/35 2755 litres used X 1.5 = 4132 litres requiredEANx 36 139 litres used X 1.5 = 209 litres requiredEANx50 397 litres used X 1.5 = 596 litres requiredOxygen 485 litres used X 1.5 = 728 litres required

OTUs = 87.9 CNS% = 47.6%

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IMPERIAL

Example: You’re planning to dive to 180 feet for 20 minutes using TMx 21/35. Your decom-pression schedule, which has the deep stops precalculated, calls for a 30 fpm ascent rate,with a one minute stop at 110 feet and one minute at 80 ft using EANx36, followed by oneminute at 60 feet, one minute at 50 feet, two minutes at 40 feet and five minutes at 30 feetwith EANx50. The final stops use pure oxygen for three minutes at 20 feet and 16 minutes at15 feet. Your SAC rate is .8 cubic feet per minute for the working part of the dive and .65 cfmwhen decompressing. Assuming a one third reserve, determine your gas volume require-ments, OTUs and CNS clock using the appropriate tables.

Dpth Tme SAC CnFct Vol. Gas PO2 OTU OTUs CNS/ CNS%mins min

180 20 .8 6.5 104 TMx21/35 1.36 1.56 31.2 .67 13.4%

145 (a) 2 .8 5.5 8.8 TMx21/35 1.16 1.27 2.54 .48 .96%

110 1 .65 4.3 2.8 EANx36 1.56 1.87 1.87 2.22 2.22%

95 (a) 1 .8 4.0 3.2 EANx36 1.45 1.7 1.7 .83 .83%

80 1 .65 3.4 2.2 EANx36 1.23 1.37 1.37 .55 .55%

60 1 .65 2.8 1.8 EANx50 1.41 1.64 1.64 .83 .83%

50 1+1 .65 2.5 3.3 EANx50 1.26 1.41 2.82 .55 1.1%

40 2 .65 2.2 2.9 EANx50 1.11 1.17 2.34 .48 .96%

30 5 .65 1.9 6.2 EANx50 .95 .92 4.6 .33 1.65%

20 3+1 .65 1.6 4.2 oxygen 1.61 1.93 7.72 2.22 8.88%

15 16 .65 1.5 15.6 oxygen 1.45 1.71 27.36 .83 13.9%

TMx21/35 112.8 cf used X 1.5 = 169.2 cf requiredEANx 36 8.2 cf used X 1.5 = 12.3 cf requiredEANx50 14.2 cf used X 1.5 = 21.3 cf requiredOxygen 19.8 cf used X 1.5 = 29.7 cf required

OTUs = 85.16 CNS% = 45.28%

DISCUSSION QUESTION (metric and imperial):

Might it be worth recalculating this dive without EANx36 as a deco gas? Why or why not? Is PO2 an issue?

[ANSWER: Since it’s only used a few minutes, you can simplify logistics by eliminating the cylinder.Also, switching that deep raises your PO2 to almost 1.6 ata – which is better to avoid after 20 minutes at 1.4 ata (working PO2 limit). However, there could be a benefit with respect to gas volume and decotime for contingency scenarios, perhaps with switching to EANx36 planned for no deeper than 24 metres/80 feet.]

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K. Team Diving I



1. What are four benefits of team diving, and how does each of

these relate to trimix diving?

2. In what ways does trimix increase the importance of compati-

ble gases within a team?

1. During the Tec Deep Diver course, you learned that tec diving is a teameffort with four primary benefits, each of which relates to trimix diving.a. Team diving has a higher likelihood of mission success based on

detailed dive planning.

• Trimix diving will increase the complexity of dive planning makingteam planning even more valuable.

b. Team diving fosters preparedness and resources for handling com-plex emergencies.

• Potential emergencies in trimix diving can be more logisticallycomplex due to depths and gas demands.

• Team resources enhance the ability to overcome these complexi-ties.

c. Team diving reduces accidents by providing a “backup brain” foreach other during predive checks and throughout the dive.

• Compared to tec diving with air/enriched air, trimix diving oftenhas more equipment, tables and plans to check and confirm.

• There are more critical steps such as gas switches, deep stops,ascent rates, etc. in a trimix dive with more potential for accident.Teams double check and confirm with each other through thesecritical steps.

d. Team diving provides the cama-raderie that comes from facing achallenge together.

• Trimix dives tend to be longer,deeper and more challengingthan air/enriched air tec dives.

• Therefore, the camaraderietends to be deeper and moremeaningful as well.

2. All team members diving with thesame gases is important in trimix diving.a. There’s less flexibility in deco schedules with trimix, so gas compati-

bility is important for allowing teammates to double check eachother’s schedules and NO TOX gas switches.

• gas switches should be made at the same depths

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• depth changes and stop times should be the same (or very similar)

• teammates signal each other when making switches

b. In an emergency, deco gases may be shared without concern abouthow it’s affecting the deco schedule.

c. Predive, teammates can check each other by matching – each diverhas the same gases in the same number of cylinders with the samelabeling.

d. Because the deco schedule will be the same (or very similar), usingthe same gases keeps the team together.

L. Thinking Like a Trimix Diver I



1. When planning a trimix dive, what aspects of the dive should

you be thinking about in a Good Diver’s Main Objective Is To

Live?

2. What makes simulation an effective training tool for learning

to dive with trimix?

3. How might you use simulation as a tool following this course?

1. When planning a trimix dive, you should be thinking about theseaspects of A Good Diver’s Main Objective Is To Live. (See theTec Deep

Diver Manual for a review of these dive planning steps.)a. Good – Gas

• How much gas volume will I need? Is itpractical to carry that many cylindersin the environment?

• Can I accomplish the mission within thegas volumes I can carry? How manydives will it take?

• How will the mission objective and con-ditions affect my breathing? Can I main-tain my normal breathing pattern?

• Have I simplified the decompression asmuch as possible?

b. Diver’s – Decompression

• Do I have adequate backup decompres-sion information?

• Would I be able to decompress if I couldn’t relocate staged deco cylinders?

• How well does a next deeper depth/next longer time schedulestack up against my planned gas volumes?

• Is trimix the appropriate gas for this dive?

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A GoodDiver’s

MainObjective

Is To Live!


c. Main – Mission

• Is the mission reasonable given the depth and decompression?

• Is trimix the appropriate gas for this dive?

• Is the mission worth the dive? Could I be more effective or lowermy risk by making two dives instead of one?

• Is the risk worth the benefit?

d. Objective – Oxygen

• Is the oxygen exposure for planned and contingency dive withinaccepted limits?

• Have I looked closely at the accumulating oxygen exposurethroughout decompression?

e. Is – Inert gas narcosis

• Will narcosis be a significant factor giventhe gas being used, the depth, the individ-uals, the conditions and the mission?

• Should a higher helium blend be used?

• Is trimix significantly advantageous?

f. To – Thermal

• Given the exposure protection, water tem-perature and dive duration, will diversmaintain adequate warmth?

• Is there a backup inflation method if argonsystem fails/exhausts without putting trim-ix in a dry suit?

• Can you reasonably simplify by making thedive in a wet suit?

g. Live – Logistics

• Does the dive require surface support? How much?

• Are support divers well briefed and prepared to assist with trimixactivities?

• Are all cylinders clearly marked and identified?

• Will there be deco software available at the dive site?

• Have all team members agreed on the gas blends to use?

• Do you have the gases and/or mixing hardware to accomplish allthe dives required?

2. Simulation for training.a. Effective diver training begins with degrees of simulation.

• As an Open Water Diver you simulated running out of air to prac-tice alternate air source use.

• During the Tec Deep Diver course, you made simulated decom-pression dives before making actual decompression dives.

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b. During this course, you’ll be simulating trimix dives before makingactual trimix dives.

c. Simulation makes an effective training tool for potentially hazardoussituations like technical diving.

• allows you to form habits with procedures before you’re in a criti-cal situation with them

• with minimal risk, you can make and learn from the same mis-takes that would be very hazardous on an actual trimix dive

• you can respond to emergencies without the actual risk of theemergency

• you can form automatic responses to situations for faster properaction when needed

• you can try, retry and practice techniques and procedures with-out the time or expense of actual trimix dives

d. During simulation training, the idea is to do everything as closely aspossible to what you would do on an actual trimix dive.

e. Obviously, you eventually have to make actual trimix dives.However, simulation allows you to learn and practice much of whatyou need to know with less risk, cost and time.

f. After you’re a certified Tec Trimix Diver, you may find it useful tosimulate dives in shallow water for reasons that might include:

• to refresh skills if you’ve not been tec diving in awhile.

• to try out new procedures, equipment or equipment configura-tions before trusting them in an actual decompression situation.

• to rehearse a complex mission.

• to allow divers to familiarize themselves with each other for sub-sequent team dives.

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IV. Practical Application OnePractical Application One has three primary purposes: 1) to give you theopportunity to check students’ equipment configurations and make adjust-ments if necessary, 2) to team build and establish camaraderie among thestudents, and 3) to get students familiar with the basics of using desktopdeco software.

To successfully complete this Practical Application, the student will be

able to:

1. Working within the student’s assigned team, rig gear, including

required stage/deco cylinders, so that it conforms with the stan-

dardized technical rigging philosophy covered in the Tec Deep

Diver course, plus meets any environment specific equipment

requirements specified by the instructor.

2. Given a dive depth, bottom time, trimix blend, two decompression

gas blends, a working SAC rate and a deco SAC rate, use desktop

decompression software to generate a decompression schedule

and contingency decompression schedules, each with gas volume

requirements (including reserves), turn pressure, OTUs and CNS

clock oxygen exposure.

3. Given a dive depth, bottom time, trimix blend, four decompression

gas blends, a working SAC rate and a deco SAC rate, use desktop

decompression software to generate a decompression schedule

and contingency decompression schedules, each with gas volume

requirements (including reserves), OTUs and CNS clock oxygen

exposure.

A. Divide the class into teams of two to four individuals. Staff membersmay participate as team members if necessary for logistics and sizing,but they should be cautious to participate as equals rather than as teach-ers/leaders.

B. In teams, have students set up their gear – everything, including mask,fins, gauges, cylinder markings and exposure suit – as if for a tec dive.They’re to rig their gear to meet the standardized technical configura-tion they learned in the Tec Deep Diver course.1. If appropriate for logistics, you may use this as equipment set up for

the Assessment Dive and/or Training Dive One.2. Encourage students to work together as a team. They may assist each

other with configuration revisions and improvements.3. This should be pretty routine for student divers at this training level.

Students qualifying for the DSAT Tec Trimix Diver course with a certifi-cation other than DSAT Tec Deep Diver may have some configurationrevisions necessary to meet this requirement.

4. Note any students with significant difficulties or problems. Any suchstudent should have remedial training, as necessary, before continu-ing in this course.

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C. Have students work in teams with desktop decompression software.1. Assign a dive depth, bottom time, trimix blend and two deco blends.2. Have team determine decompression schedule, OTUs, CNS clock

and gas volume requirements (with thirds reserve) and turn pres-sures for each student based on each student’s working and decoSAC rates, and cylinders used. You may assign SAC rates for studentdivers who don’t know theirs. a. Although working in a team, each student should take a turn

working at the keyboard to enter the data and generate theschedules, volumes, etc.

b. Each team should be able to show you a single decompressionschedule with the different gas volume requirements for each student. (Three gas volume requirement reports.)

c. You may have students use this schedule for the simulated decom-pression in Training Dive One.

3. Have team determine contingency decompression schedules basedon the next deeper depth, next longer time and next deeper depthand longer time, along with gas volume requirements for each

student diver.a. Although working in a team, each student should take a turn

working at the keyboard to enter the data and generate theschedules, volumes etc.

b. Each team should generate three contingency decompressionschedules, with the different gas volume requirements: the nextdeeper depth, the next longer time and the next deeper depthand longer time, for each student. (E.g. a team of three would havethe three schedules, plus nine gas volume requirement reports tocover the differing SAC rates of each student.)

4. Assign a dive depth, bottom time, trimix blend and four decoblends.

5. Have team determine decompression schedule, OTUs, CNS clockand gas volume requirements (with thirds reserve) and turn pres-sures for each student based on each student’s working and decoSAC rates and cylinders used. You may assign SAC rates for studentswho don’t know theirs. a. Although working in a team, each student diver should take a

turn working at the keyboard to enter the data and generate theschedules, volumes, etc.

b. Each team should be able to show you a single decompressionschedule with the different gas volume and turn pressurerequirements for each student. (Three gas volume requirementreports.)

c. You may have student divers keep this schedule for use as the sim-ulated trimix dive in Training Dive One. If, due to local practices,

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each student will only have two deco cylinders in Training DiveTwo, then you may also assign a two deco gas dive for them to planas the simulated trimix dive, but they must still demonstrate theplanning of a four gas dive to meet the requirements of thisPractical Application.

6. Have team determine contingency decompression schedules basedon the next deeper depth, next longer time and next deeper depthand longer time, along with gas volume requirements for each

student.

a. Although working in a team, each student should take a turnworking at the keyboard to enter the data and generate the schedules, volumes, etc.

b. Each team should generate three decompression schedules withthe different gas volume requirements on all three contingenciesfor each student. (Nine gas volume requirement reports.)

c. You may have students keep these schedules for use in the simulat-ed trimix dive in Training Dive Two.

7. At your discretion, you may have students calculate one or more pro-files manually for practice, to simulate not having access to desktopdeco software for individual gas supply calculation, and to comparewith the software results (which will differ somewhat).

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V. Assessment Dive

The Assessment is required for students entering the Tec Trimix Diver

course with a qualifying prerequisite certification from another train-

ing organization. It is required for Tec Deep Diver certified students

who have not made a technical decompression dive requiring a decom-

pression cylinder to 40 metres/130 feet or deeper within the previous

six months. You may require Tec Deep Diver certified students to com-

plete this dive in any case for assessment, refresher or other purposes.

Some students may

request it as well. It is rec-

ommended that prior to

this dive, you schedule

ample time for students

entering the Tec Trimix

Diver course with a quali-

fying prerequisite certifi-

cation to read the Tec

Deep Diver Manual and

view the TecRec

Equipment Setup and Key

Skills video.

The Assessment Dive is

sequenced in the course

outline as following

Knowledge Development

One and Practical

Application One. However, you may sequence it prior to either or both of

those, provided students have met the course prerequisites, medical

requirements, etc.

To successfully complete the assessment dive, the student will be

able to:


stage/deco cylinders, and plan the dive following the A Good

Diver’s Main Objective Is To Live procedure, and perform

predive checks following the Being Wary Reduces All Failures

procedures.

2. Working in a team, perform a bubble check, descent check and

S-drill.

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[Note to instructor: This assessment dive has the primary

goal of letting you assess whether a student diver has the

skill level expected of a Tec Deep Diver. Use this dive to

observe each student diver, being alert for any who may need

remedial training prior to further training.]


3. Respond to a simulated out of gas emergency, as both donor

and receiver, with receiver switching to donor’s long hose sec-

ond stage, then swimming 30 metres/100 feet and maintaining

contact with the teammate.

4. Shut down both manifold valves and the isolator valve, switch-

ing second stages to maintain a breathing supply, beginning

with any valve chosen by the instructor, within 60 seconds.

5. Deploy a lift bag from the bottom in water too deep in which to

stand.

6. Tow a simulated, unresponsive breathing diver horizontally 6

metres/20 feet.

7. On the bottom, independently don, remove and redon two

stage/deco cylinders.

8. Maintain neutral buoyancy and avoid bottom contact while

swimming 60 metres/200 feet wearing two stage/deco cylinders.

9. While simulating an ascent with abbreviated stop times along a

bottom, perform gas switches to two worn deco cylinders fol-

lowing the NO TOX procedure.

10. Simulate a four stop decompression ascent along a line switch-

ing deco cylinders at each simulated stop following the NO TOX

procedure, including a final stop of at least 10 minutes main-

tained only through buoyancy control (no physical contact),

staying within plus/minus 1 metre/3 feet of stop depth during

gas switches and within plus/minus .6 metres/2 feet variation

after gas switches.

11. Don and remove two stage/deco cylinders at the surface in

water too deep to stand in.

12. Demonstrate time, depth and gas supply awareness by record-

ing depth, SPG pressure and time at intervals set before the dive

by the instructor.

A. Assessment Dive Standards

1. The Assessment Dive is a no stop dive conducted in confined water,

limited open water or open water. (See Section Two, Course

Standards for definitions of these.) The maximum depth is 18 metres/

60 feet. It’s recommended that the site provide ready access to water

shallow enough to stand up in. If conducting this dive in open water,

the intent is to use conditions well within students’ experience and

abilities so that you can clearly observe their skill performance with-

out substantial environmental effects.

2. Ratios – 6 students to 1 instructor, with 2 more students permitted

with a certified assistant to a maximum of 8. (See Section Two for

specific requirements necessary to qualify as a certified assistant in

this course.) These are maximums – reduce ratios as necessary to

accommodate student diver characteristics and environmental/logisti-

cal considerations.

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3. Students and instructor must be equipped as described in the Tec

Deep Diver course, with accommodation for environmental needs.

This includes but is not limited to:

a. Manifolded double cylinders with dual, independent regulator

posts.

b. Technical diving BCD, redundant

buoyancy device (double bladder

BCD, or dry suit if appropriate for

weight of gear worn) and harness

as described in the equipment

requirement section, and following

the rigging philosophies described

in the Tec Deep Diver course.

c. Two stage/decompression cylin-

ders configured as described in the

equipment requirement section,

and following the rigging philoso-

phies described in the Tec Deep Diver course.

4. Gas requirements. Student divers and staff may use air or

enriched air, any suitable blend, in sufficient supply to accom-

plish the dive objectives, and all breathable to 18 metres/60 feet.

If all are the same or similar blends, have students mark the deco

cylinders with simulated gases of differing oxygen content and

simulated maximum depths. These may be blends such as EANx 32,

36, 50 and oxygen, with students marking cylinders with the real

blend and then noting SIM: EANx32, etc. Back gas should be simu-

lated or actual 21 percent oxygen.

B. Predive Planning, Briefing and Preparation – suggested sequence

1. Predive briefing

a. Group in teams, student divers set up their rigs, analyze gases,

but do not yet don exposure suits.

• Encourage teamwork.

• Inspect each rig for correct setup, ample gas supply, etc. Pay

particular attention to proper cylinder markings written and

placed so team can read them while worn.

b. Dive site overview

• Depth, temperature, entry/exit points, noteworthy features.

• Facilities – parking, lockers, boat dry and wet areas, where to

find emergency equipment, etc.

c. Dive overview

• Depth/time limits (limited open water)

• It’s recommended that you have students write down the dive

overview and notes on a slate for reference during the dive,

and to have them do this for each dive.

padi.com 3-31


• Skill overview – describe each skill’s performance requirements.

Since these are skills that divers should have already, it’s recom-

mended that you have students plan the dive sequence, demonstra-

tions, etc. This should be well within their capabilities.

– don stage/deco cylinders at surface in water too deep to

stand in

– bubble check, descent check

– S-drill: signal, out of gas – use long hose as donor and as

receiver, swim horizontally 30 metres/100 feet

– gas shutdown drill

– unresponsive diver tow underwater 6 metres/20 feet

– deploy lift bag

– simulated decompression ascent (abbreviated stop times

acceptable) along bottom performing NO TOX gas switches at

each simulated depth

– simulated decompression ascent along line, with final 10

minute neutral buoyancy stop with gas switch

• provide students with the four stop schedule they’ll follow

– remove deco cylinders at the surface in water too deep to

stand in

• Time, depth and gas supply awareness – assigned by instructor.

– May be depths, times, pressures, turn pressures, etc. Goal is to

get divers to constantly monitor time, depth and gases.

– Staff should not remind divers to do this.

– Teammates are encouraged to assist each other with this.

– Students must do this no matter what else is going on, short of

a real emergency.

• Review hand signals, emergency protocols, descent and ascent pro-

cedures, final details. Assign each team to complete individual dive

plans.

d. Teams plan dives and gear up

• Teams go through A Good Diver’s Main Objective Is To Live and

plan dive. Have them plan based on a four stop deco schedule

you provide. They should generate an entire plan with deco sched-

ule and gas volume requirements for each diver. You may have

them do this by hand or use desktop deco software. Allow ample

time for proper planning, which may take an hour or more. The

final plans should include gas volume requirements for all divers

and may be presented on the TecRec Dive Planning Slate and/or on

a computer printout. It’s also recommended that you have students

laminate copies of the deco schedule to carry on the dive. The dive

should include a mission (measuring, assembling something, figur-

ing out a puzzle, etc.) they can reasonably expect to complete with-

3-32 padi.com


in the bottom time of the simulated dive.

• Teams gear up and finish their checks with Being Wary

Reduces All Failures.

– Student divers use TecRec Equipment Checklist to confirm

each other’s equipment setup.

– Touch drill while geared up and seated, students reach back

and touch (grasp) regulator and isolator valves as if to

close/open them.

– Teammates adjust equipment/assist each other as necessary.

C. Assessment Dive — sequence may vary depending upon the dive plan

1. Entry – appropriate for environment

a. Divers check their weight if necessary due to environment or gear

change.

b. Don stage/deco cylinders in water too deep to stand in.

c. Divers bubble check teammates. It’s a good idea to have spare

O-rings at hand.

2. Descent to insensitive bottom

(limited open water)

a. Descent check

b. Position class for skills

3. Dive skills – instructor demos (if nec-

essary) and has students perform.

a. S-drill: Out of gas drill as donor

and receiver – pairs swim horizon-

tally 30 metres/100 feet maintain-

ing contact, then switch roles.

Watch for signalling, smooth

deployment, hose trapping and

other problems that interfere with

a seamless drill.

b. Gas shut down drill – On bottom,

student divers close and reopen both regulator valves and isola-

tor valve, switching second stages to stay with the open valve,

within 60 seconds. You may have some students start with second-

ary regulator and others with primary. This is a skill that tends to

deterioritate with disuse; it’s acceptable to allow a student to repeat

the drill to meet the requirement, but if unable to do so after two or

three times, separate remedial training may be necessary.

c. Unresponsive diver tow underwater

• Diver makes self and “victim” neutrally buoyant, hold reg in

victim’s mouth and tows over bottom 6 metres/20 feet.

• Be prepared to assist if student makes self or “victim” too buoy-

ant. Watch for holding second stage in victim’s mouth.

padi.com 3-33


• Caution student divers to not overexert or get out of breath – swim

at a pace that avoids overexertion.

d. Deploy lift bag

• Student divers practice retrieving bags, reels and sending up bag.

• In a pool, use deepest water possible.

• Watch for buoyancy control problems.

• This is a skill that students without Tec Deep Diver training fre-

quently need remediation on.

e. Simulated decompression ascent (abbreviated stop times) along

bottom performing NO TOX gas switches at each simulated depth

• As necessary designate areas that represent the “bottom” and deco

stops appropriate for switches to deco gases (as simulated or

actual).

• Working in teams, student divers start at the “bottom” and

“ascend” to each “stop” and NO TOX gas switch to each simulated

EANx/oxygen mix.

• After all teammates complete a switch, students wait one minute

before ascending to next stop. Full stop duration isn’t being simu-

lated.

• After final stop, divers replace cylinders to their personal standard

starting positions, then descend to “bottom” and repeat drill.

• Watch closely that students actually follow all NO TOX steps exact-

ly and in order. Have those who fail to repeat the drill until they

perform all stops following the procedure correctly.

• Repeat this drill until all divers handle cylinders and make switches

correctly and fluidly.

f. Simulated decompression ascent along line,

with final 10 minute neutral buoyancy stop

with gas switch

• Deploy a vertical weighted line with buoy

as an ascent line. Mark the line (knot, clip,

cable tie, etc.) with simulated or actual

stops at 12 metres/40 feet, 9 metres/30

feet, 6 metres/20 feet and 5 metres/15 feet.

• All stops should be far enough off the bot-

tom that students do not make bottom

contact.

• You may mark only one or two stops (depending upon the pool/lim-

ited open water depth) and have student descend and reascend to

simulate their continued ascent.

• At each stop, working as a team, students signal and NO TOX

switch to the appropriate deco gas and decompress according to

the schedule you give them.

3-34 padi.com


• Student divers should not vary more than 1 metre/3 feet from the

stop depth during gas switches nor more than .6 metres/2 feet after

completing gas switch. Encourage teammates to help each other

maintain depth during switches and decompression.

• The final stop should include 10 minutes maintained at stop depth

by buoyancy control only – no physical contact (visual reference

acceptable). This may be difficult for some divers. You may need to

repeat this one or more times before progressing to Training Dive

One.

g. Remove deco cylinders at the surface.

• Student divers establish positive buoyancy and hand cylinders up

to surface personnel, or hang them on a gear line, as they remove

them in the water.

4. Exit water (as appropriate for environment).

D. Post Dive

1. Performance review. After giving divers some time to rest, get a drink,

etc., but while memories remain fresh, have teams identify what hap-

pened, what they learned, what worked and what didn’t, etc. Comment

and fill in missing information as necessary, but have students critique

themselves constructively while you guide the process.

2. Have divers show you their slates with the recorded

times/depths/SPG readings assigned prior to the dive.

3. Divers disassemble and stow their gear as appropriate.

4. Student divers log dive for your signature.

5. Divers who do not meet the performance requirements must retrain

until they demonstrate mastery before beginning Training Dive One.

As appropriate, this can be an extra session (to handle one or two prob-

lem skills) or repeating portions, or even all of, the Tec Deep Diver course

(to handle multiple problem skills, a failure to follow procedures, etc.).

VI. Training Dive One

To successfully complete this training dive, the student will be able to:



Diver’s Main Objective Is To Live procedure, and perform predive

checks following the Being Wary Reduces All Failures proce-

dures.

2. Working in a team, perform a bubble check and descent check.

3. With minimal assistance, remove and replace four stage/deco

cylinders on the bottom, and swim 60 metres/200 feet wearing

four stage/deco cylinders with adequate buoyancy control to

minimize bottom contact or unplanned ascent.

4. Swim at least 18 metres/60 feet sharing gas with the long hose as

both a donor with a mask and a receiver without a mask.

padi.com 3-35


5. With minimal assistance, remove and replace four stage/deco

cylinders while wearing no mask.

6. As part of a team, respond appropriately to spontaneous drills

throughout the dive, including but not limited to free flowing

regulator, failed manifold, teammate switching to wrong gas

and failed lift bag.

7. Shut down both manifold valves and the isolator valve, switch-

ing second stages to maintain a breathing supply, beginning

with any valve chosen by the instructor, within 45 seconds.

8. Deploy a lift bag from the bottom in water too deep in which to

stand.

9. Conduct a simulated trimix dive, including simulated midwater

decompression stops and gas switches along a line or other

vertical reference, not varying more than

.6 metres/2 feet from each stop depth.

10. While maintaining stop depth varying no

more than 1 metre/3 feet, shut down both

manifold valves and the isolator valve,

switching second stages to maintain a

breathing supply, beginning with any valve

chosen by the instructor, with no time

limit (gas shutdown drill).

11. At the surface while in full tec gear includ-

ing at least two stage/deco cylinders, tow

a simulated unresponsive, non breathing

diver also in full tec gear including at

least two stage/deco cylinders, 60

metres/200 feet while removing all equip-

ment from self and towed diver, and giving

rescue breaths every five seconds.

12. Demonstrate time, depth and gas supply

awareness by recording depth, SPG pres-

sure and time at intervals set before the

dive by the instructor.

A. Training Dive One Standards

1. Training Dive One is a no stop dive conducted in confined water or

limited open water. (See Section Two, Course Standards for definitions

of these.) The maximum depth is 10 metres/30 feet.

2. Ratios – 6 students to 1 instructor, with 2 more students permitted





cal considerations.

3-36 padi.com

TRAINING DIVE ONE

• Entry • Descent• Descent check• Remove stage/deco cylinders on

the bottom• Long hose, no mask swim• Replace four stage/deco cylinders

and swim 60 metres/200 feet.• Remove and replace four stage/

deco cylinders with no mask.• Gas shutdown drill• Lift bag deployment• Simulated trimix dive with simulat-

ed decompression and ascent• Unresponsive, non breathing diver

at the surface• Exit water

POST DIVE• Performance review• Divers disassemble and stow their

gear as appropriate.• Log dive for instructor signature.






posts.

b. Technical diving BCD, redundant buoyancy device (double blad-

der BCD, or dry suit if appropriate for weight of gear worn) and

harness as described in the equipment requirement section, and

following the rigging philosophies described in the Tec Deep

Diver course.

c. Two stage/decompression cylinders configured as described in

the equipment requirement section, and following the rigging

philosophies described in the Tec Deep Diver course. This dive

orients students to handling four cylinders, which is accomplished

by having students share cylinders for the skill. You may assign

each student four cylinders at your option for the four cylinder

handling exercises; if you do so, then aluminum cylinders are

recommended.

4. Gas requirements. Student divers and staff may use air or enriched

air, any suitable blend, in sufficient supply to accomplish the dive

objectives, and all breathable to 10 metres/30 feet. If all are the

same or similar blends, have students mark the deco cylinders with

simulated gases of differing oxygen content and simulated maximum

depths. These may be blends such as EANx 32, 36, 50 and oxygen, with

students marking cylinders with the real blend and then noting SIM:

EANx32, etc. Back gas should be a simulated trimix but actually air

or enriched air and marked accordingly. The

simulated gas designations should match the

gases for the trimix deco schedule students

will follow during Training Dive Two.

B. Predive Planning, Briefing and Preparation –

suggested sequence

1. Predive briefing

a. Group in teams, student divers set up their

rigs, analyze gases, but do not yet don expo-

sure suits.


• Inspect each rig for correct setup, ample

gas supply, etc. Pay particular attention to

proper cylinder markings written and

placed so team can read them while worn.



• Facilities – parking, lockers, boat dry and wet areas, where to find

emergency equipment, etc.

padi.com 3-37


c. Dive overview (no decompression dive)

• Depth/time limits (limited open water)


overview and notes on a slate for reference during the dive, and

to have them do this for each dive.

• Skill overview – describe each skill, the performance requirement

and how you’ll conduct it, including signals, etc.

– don stage/deco cylinders at surface

– bubble check and descent check

– remove stage/deco cylinders on the bottom

– no mask long hose gas sharing as donor and receiver

– replace stage/deco cylinders on the bottom, swim 60 metres/

200 feet neutrally buoyant

– no mask remove and replace four stage/deco cylinders

– gas shutdown drill within 45 seconds

– lift bag deployment

– simulated trimix dive with midwater decompression

– midwater gas shutdown drill

– unresponsive, non breathing tec diver at the surface

• Surprise drills including but not limited to free flowing regula-

tor, failed manifold, teammate switching to wrong gas and

failed lift bag will take place throughout the dive.

• Time, depth and gas supply awareness – assigned

by instructor.

– May be depths, times, pressures, turn pressures,

etc. Goal is to get divers to constantly monitor

time, depth and gases.

– Instructor will not remind divers to do this.

– Teammates are encouraged to assist each other

with this.

– Student divers must do this no matter what else

is going on, short of a real emergency.

– This exercise stops after the simulated dive and does not con-

tinue through the unresponsive diver at the surface exercise.

• Review hand signals, emergency protocols, descent and ascent

procedures, final details. Assign each team to complete individual

dive plans.



plan dive. Have them plan based on a decompression schedule

they generate from a depth, trimix and four deco gases (as simu-

lated) that you provide. They should generate an entire plan

3-38 padi.com


with deco schedule, contingency schedule, gas volume require-

ments, turn pressures and oxygen exposure for each diver. You

may have them do this by hand or use desktop deco software, or

you may have them use the schedule and plans from Practical

Application One, if appropriate. Allow ample time for proper plan-

ning, which may take an hour or more. The final plans should

include gas volume requirements for all divers and may be pre-

sented on the TecRec Dive Planning Slate or on a computer print-

out. It’s also recommended that you have students laminate

copies of their tables to carry on the dive.

• Teams gear up and finish their checks with Being Wary Reduces

All Failures.

– Students use TecRec Equipment Checklist to confirm each

other’s equipment setup.



close/open them.


C. Training Dive One – suggested sequence

1. Entry – appropriate for environment, deep water entry recommended.


change.

b. Divers don stage/deco cylinders at surface with minimal assis-

tance.


O-rings at hand.

2. Descent to insensitive bottom (limited open water)

a. Descent check

b. Position class for skills

3. Dive skills – for each, instructor demos, then has student divers perform.

a. Remove stage/deco cylinders on the bottom

• Students place cylinders in a secure place, checking that the

valves are closed.

b. Long hose, no mask swim

• Receiver removes mask and signals “out of gas.”

• Donor provides long hose, both swim together for 18 metres/

60 feet.

• Repeat until all students conduct drill as both donor and receiver.

c. Replace four stage/deco cylinders and swim 60 metres/200 feet.

• Unless students have four cylinders each, have teammates share

cylinders for this and the next skill, then switch.

• Students don cylinders using all left/right-left, trailed/untrailed

cylinder configurations as preferred and/or briefed.

padi.com 3-39


• For right-left, remind divers “right-rich, left-lean.”

• Allow students ample time to try different configurations. Remind

them they’ll need to settle on one configuration they like and

stick with it as a personal standard.

• After they’re comfortable with configuration, students swim in a

circle, line or course, accompanied by teammates and/or staff,

60 metres/200 feet.

• Goal is to familiarize students with handling four cylinders so

they learn to maintain adequate buoyancy control to minimize

bottom contact or unplanned ascent. It also introduces them to

the drag and complexity of wearing four stage/deco cylinders.

d. Remove and replace four stage/deco cylinders with no mask.

• Student divers remove mask, then remove and replace all cylin-

ders to their correct configuration.

• Successful performance requires little or no assistance.

• Allow ample time.

e. Gas shutdown drill

• Student divers should be able to complete in 45 seconds.

f. Lift bag deployment

• Student divers should be able to do this with little difficulty.

• Have students retrieve and restow lift bags for use during simulat-

ed trimix dive.

g. Simulated trimix dive

• Bring divers to the surface in water too

deep to stand. They make the dive as

though the bottom time starts when they

reach the bottom.

• Start the dive. Divers reach the bottom

and conduct their mission.

• Divers are to deploy a single lift bag per

team to ascend along. They should do

this following the schedule.

• If necessary for logistics and time, you

can brief students to simulate a longer

bottom time than actual. (E.g., for a 20

minute bottom time, tell them to have an

actual bottom time of 10 minutes but to simulate decompression

for 20 minutes.)

• After they deploy the lift bag, mark the line (knot, clip, cable tie,

etc.) with simulated stops at 12 metres/40 feet, 9 metres/30 feet,

6 metres/20 feet and 5 metres/15 feet. Teammates assist reel diver

with depth control.

• Do not shorten decompression stops.

3-40 padi.com


• All stops should be far enough off the bottom that student divers

cannot make bottom contact.

• You may mark only one or two stops (depending upon the

pool/limited open water depth) and have students descend and

reascend to simulate their continued ascent.

• At each stop, working as a team, student divers NO TOX switch to

the appropriate deco gas and decompress according to the sched-

ule you give them. If students are wearing four cylinders, you may

have them do four switches and handle cylinders accordingly.

• Students should not vary more than 1 metre/3 feet from the stop

depth during gas switches nor more than .6 metres/2 feet after

completing gas switch. Teammates signal and help each other


• During the decompression, have each student complete the gas

shutdown drill. Students must not vary more than 1 metre/3 feet

from stop depth. Teammates may assist depth control. There is

no time limit.

• Divers complete the entire decompression and surface. Watch for

stop depth control and proper NO TOX gas switches.

4. During Training Dive One, every team should have to respond

correctly to each of the following emergencies at least once:

• free flowing regulator

• failed manifold

• teammate switching to wrong gas

• failed lift bag

a. These may occur at any point, including during the simulated trimix

dive (during the simulated trimix dive you may want to avoid prob-

lems that would cut the dive short, however).

b. Brief students ahead of time how you will assign problems (slate,

holding in purge button, etc.).

c. You may repeat spontaneous problems and assign additional ones as

you see fit.

5. Unresponsive, non breathing diver at the surface

a. Explain to students that this is simply a review of what they have

already been trained to do as PADI Rescue Divers, but a chance to

apply it to a tec diving situation.

b. In pairs of rescuers and victims, rescuer initiates as if they have just

surfaced together.

c. Watch for initial check for breathing, establishing buoyancy, calling

for help, two slow initial breaths, breaths every five seconds, and

maintaining and protecting an open airway.

d. Rescuer removes own and victim’s equipment and tows victim

60 metres/200 feet. Assign gear handlers as appropriate.


padi.com 3-41


D. Post Dive






2. Have divers show you their slates with the recorded times/depths/

SPG readings assigned prior to the dive.


4. Students log dive for your signature.

VII. Knowledge Development Presentation Two

A. Equipment II – Fullface masks and multigas dive computers

Learning Objectives: By the end of this section,

you should be able to answer these questions:

1. What is the primary advantage of using a

fullface mask for trimix diving?

2. What are two primary considerations in

using a fullface mask for trimix diving?

3. What are two primary advantages of diving

with a multigas trimix computer?

4. How do you plan dives with a multigas com-

puter?

5. How do you backup a multigas computer

when diving with trimix?

1. Fullface masks

a. The primary advantage of using a fullface mask is to reduce drown-

ing risk in the case of a CNS convulsion or other loss of conscious-

ness such as hypoxic blackout.

• may allow additional comfort in colder water

• may be fitted with voice communication electronics

• CNS risk may be higher during trimix dive due to longer decom-

pressions; fullface mask may reduce the risk of drowning should

CNS toxicity occur

b. Considerations when using fullface masks with trimix

• gas switches – you will need to switch gases, at least for air

breaks

– use of valving and switch blocks not favored in tec diving due

to configuration complexity and error potential

– a conventional fullface mask may require entirely removing the

mask one or more times during the dive – not typically preferred

for tec diving

• gas sharing – fullface mask should not interfere with the ability to

provide gas to a teammate in an emergency

3-42 padi.com


– conventional fullface masks are not typically well suited to gas

sharing in a conventional tec diving manner

• using fullface masks compatible with tec diving

– a fullface mask compatible with tec diving allows use of stan-

dard second stages and no significant procedural changes

– at this writing, at least one version (the Kirby Morgan

M-48) exists

– with M-48, you can breathe

from a standard second stage,

or second stage with M-48

mouthpod attached

– with M-48, you use mouthpods

for easy gas switches with full-

face mask risk reduction

– divers not using M-48 mask

can still breathe from the

M-48 mouthpod (it has a

mouthpiece)

– usual tec procedure with M-48

is to use standard second

stage (no mouthpod) for bot-

tom gases (long hose, secondary and travel gases) and mouth-

pods for deco gases (highest CNS risk)

2. Multigas trimix computers

a. At this writing, several multigas trimix computers have entered the

market

• You can program these computers with seven or more gas

blends: oxygen, enriched air, air or trimix.

• During the dive, the computer calculates your decompression

based on the actual dive depth, time and gases you use (switch

the computer as you switch gases per manufacturer instructions)

• Some interface with desktop deco software.

b. Two primary advantages of diving with multigas trimix computers

• Precision – Your deco schedule is based on your actual dive pro-

file; especially useful in caves, wrecks and other dives that follow

varied contours.

• Simplifies some emergency situations

– if you switch to a low oxygen gas because of CNS concerns, the

computer calculates your decompression based on the lower

oxygen gas (as opposed to simply stopping the deco clock)

– with a deco gas problem (lost, runaway regulator, etc.), com-

puter calculates deco with the gases you have (including back

gas if necessary)

padi.com 3-43


– extra gas compatibility in an emergency – you program com-

puter with additional gases (e.g. Your team is using four gases

but your computers allow seven: TMx 21/50, EANx36, EANx50

and oxygen. However, there’s also EANx32 and air available;

you set these in two of the “extra” gas choices so that comput-

er can calculate your decompression with them should they be

needed in an emergency.)

c. Planning dives with multigas trimix computers

• You plan dives using desktop deco software.

– multigas dive computers do not calculate gas supply require-

ments

– predive planning modes don’t usually allow easy comparison of

differing gases, depths, etc.

– you usually want backup tables anyway (they’re required with

only a single computer)

• With experience, you’ll learn which desktop deco software algo-

rithm (if the type you’re using offers a choice) most closely

matches your multigas dive computer – generally start conserva-

tive.

d. Backing up a multigas trimix computer

• Simplest method is to have two multigas trimix computers, ideally

the same model, or at least two with same decompression model

(also most expensive option)

– Two computers, even of the same model, are seldom exactly

identical in their profile (though they shouldn’t differ much);

obviously you decom-

press according to the

more conservative one.

• With only one computer,

you carry contingency

tables you generate with

desktop deco software dur-

ing predive planning.

• Many divers carry contin-

gency tables even if they

have the two computers,

since they’re generating

them anyway as part of

dive planning.

3-44 padi.com


B. Gas Planning II – Properties of helium, ENDs, choosing bottom and deco

gases, hypoxic gas blends



1. What four characteristics of helium relate to its use as a dive

gas?

2. What are the two primary advantages of helium as a dive gas?

3. What are four disadvantages of helium as a dive gas?

4. What is isobaric counterdiffusion and how do you avoid it?

5. How can putting trimix in your dry suit cause a decompression

problem?

6. What is an END (Equivalent Narcotic Depth), and how do you

determine it?

7. What four considerations do you apply in selecting a trimix?

8. What is meant by “ideal mix”? For what reasons is the “ideal

mix” often not ideal?

9. What is meant by a “hypoxic” trimix?

10. What is a “travel gas”?

11. When do you need a travel gas?

12. What is the recommendation regarding using air or enriched

air for a repetitive dive after a trimix dive?

1. The following characteristics of helium relate to its use as a dive gas:

a. Helium doesn’t dissolve in lipids as readily as nitrogen or oxygen.

Solubility in lipids is associated with a gas’ narcotic potential.

b. Helium is less dense than nitrogen or oxygen.

c. Helium diffuses more rapidly than nitrogen or oxygen.

• Graham’s Law of Diffusion states that the relative rates of diffu-

sion of two gases is inversely proportional to the square roots of

their densities.

• helium’s density (grams/litre) approx = .18, square root .42

• nitrogen’s density (grams/litre) approx = 1.3, square root 1.14

• oxygen’s density (grams/liter) approx = 1.4, square root 1.18

• All else being equal, helium diffuses more than 2.5 times as fast as

oxygen or nitrogen.

d. Helium conducts heat faster than nitrogen/oxygen do.

2. Primary advantages of helium as a dive gas:

a. Helium doesn’t cause narcosis (at least within the depths frequent-

ed by tec divers), which is one of the primary purposes of trimix.

• theorized that this is due to poor lipid solubility (Meyer-Overton

hypothesis)

• can cause High Pressure Nervous Syndrome (HPNS – effect on the

nervous system characterized by tremors, nausea, dizziness,

fatigue, muscle twitching), but typically at depths well below the

padi.com 3-45

norm for tec diving (but within commercial diving heliox range –

generally below 125 metres/400 feet)

b. Helium requires less effort to breathe when diving deep due to its

lower density. This reduces fatigue and saves energy.

3. Disadvantages of helium as a dive gas:

a. Within the depths/times common to tec diving, helium’s rapid diffu-

sion makes trimix dives longer than comparable air/enriched air

dives because more gas goes into solution and must come out of

solution during decompression.

• This is because the pressure gradient driving the helium into

solution into body tissues at depth will be greater than the pres-

sure gradient driving the helium out of solution during

ascent. Therefore, the high gradient plus rapid

diffusion means more helium goes into solution

than would nitrogen, all things being equal.

During ascent, however, the gradient is less, and

not enough to force the helium to dissolve out of

solution as fast as it went in despite its diffusion

rate. Helium may therefore ingas so much faster

than outgas that it takes longer to decompress than

with a comparable dive made using a comparable

amount of nitrogen.

• EXAMPLE: According to one desktop deco software set on a

conservative Buhlmann algorithm, a dive to 60 metres/200 feet for

40 minutes, with deco on EANx36, EANx50 and oxygen:

– 80 minutes deco using air as bottom gas

– 91 minutes deco using TMx21/35 as bottom gas

– 123 minutes deco using TMx21/70 as bottom gas

• Note that all three examples have the same oxygen (21 percent)

and therefore the same fraction of inert gas; the deco time rises

with more helium and less nitrogen.

• Note that because of helium’s rapid diffusion, very long dives that

approach saturation have shorter decompression times with trim-

ix than with a comparable air/enriched air. However, the bottom

times for this are several hours long – beyond what’s common in

tec diving. Using the same model and deco gases as above, a dive

to 60 metres/200 feet for 720 minutes requires deco of:

– 48 hours, 50 minutes using air as bottom gas

– 34 hours, 04 minutes using TMx21/35 as bottom gas

– 28 hours, 49 minutes using TMx21/70 as bottom gas

b. Helium’s rapid diffusion makes it less forgiving compared to air in

case of decompression errors.

• Because helium diffuses rapidly, it forms bubbles more easily.


3-46 padi.com

Helium Atom


• This means less error tolerance of decompression errors, such

ascending past stop depth (even despite returning immediately),

because bubbles can form more quickly.

• Helium mixes are known for producing DCS symptoms while still

decompressing. This is relatively rare with oxygen-nitrogen

blends (except when large amounts of decompression have been

omitted).

c. Helium’s rapid diffusion rate makes isobaric counterdiffusion (a.k.a.

inert gas counterdiffusion) a theoretical concern.

• An issue if switching from a slow diffusing gas to a fast diffusing

gas during decompression, such as making an air/enriched air

dive and using trimix during decompression.

• Helium diffuses into the tissues faster than nitrogen diffuses out,

making the total dissolved inert gas high, possibly leading to bub-

ble formation and DCS.

• Not generally a significant issue with the standard practice of

switching from a fast diffusing gas (helium in TMx) to a slow dif-

fusing gas (nitrogen in EANx) during decompression. (Note: Inner

ear DCS commonly results after switching to air or EANx from

heliox. The theory is that because heliox trapped in the ear is in

gas form, it doesn’t diffuse out rapidly, but nitrogen diffuses in,

raising the inner ear’s inert gas pressure.)

• This is one reason why gas compatibility between teammates is

important – in a gas sharing emergency, it creates a risk for a

diver using EANx/air as bottom mix to breathe the long hose of

TMx diver.

• Isobaric counterdiffusion can also be an issue by causing DCS

through counter diffusion through your skin if you’re surrounded

by a rapidly diffusing gas (helium/TMx) while breathing a slow

diffusing gas (air/EANx). This is primarily an issue if you put heli-

um in a dry suit (which you wouldn’t do anyway). Not generally

an issue with argon (very slow diffusion) or wet suits.

d. As you already learned, helium’s heat absorbing characteristics (as

well as isobaric counterdiffusion) makes it inappropriate for a dry

suit inflation gas.

• As you know, trimix requires a separate inflation system, with

argon the most common because it has better insulating capabili-

ties than air/EANx.

• Some TMx divers put an inflator hose on an EANx deco cylinder

as a backup inflation source.

4. ENDs (Equivalent Narcotic Depths)

a. For a given depth using TMx, an END (Equivalent Narcotic Depth) is

the depth at which you would expect the same narcosis if diving

with air.

padi.com 3-47


b. END can be calculated assuming that oxygen is, or is not, narcotic.

• Because oxygen appears to be as or slightly more narcotic than

nitrogen, the prevailing method is to treat oxygen as narcotic.

• Desktop deco software usually determines ENDs. You may need to

select whether it treats oxygen as narcotic.

c. END is calculated by finding the absolute partial pressure (in msw

or fsw) of the nitrogen/oxygen portion of trimix at a given depth,

and then determining the depth at which that partial pressure is the

total pressure.

• METRIC

END = [(1 – fraction of He) X (D + 10)] – 10

EXAMPLE: What is the END at 50 metres when diving TMx 18/33?

END = [(1 – .33) X (50 + 10)] – 10

END = [(.67) X (60)] – 10

END = 40.2 – 10

END = 30.2 metres

• IMPERIAL

END = [(1 – fraction of He) X (D + 33)] – 33

EXAMPLE: What is the END at 165 feet when diving TMx 18/33?

END = [(1 – .33) X (165 + 33)] – 33

END = [(.67) X (198)] – 33

END = 132.7 – 33

END = 99.7 feet

• For simplicity, use the Equivalent Narcotic Depth table (metric or

imperial) in the Tec Trimix Diver Manual.

5. Several factors go into selecting the gases you will use on a given dive,

as well as at what depth you will make gas switches. The gases you

choose will be a judgment that balances these four considerations:

a. Narcosis

• What is the planned depth?

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TRIMIX EQUIVALENT NARCOTIC DEPTH TABLE – METRIC

Fraction Depth MetersHe 24 27 30 33 36 39 42 45 48 51 54 57 60 63 66 69 72 75 78 81 84 87 90

10% 21 23 26 29 31 34 37 40 42 45 48 50 53 56 58 61 64 67 69 72 75 77 8011% 20 23 26 28 31 34 36 39 42 44 47 50 52 55 58 60 63 66 68 71 74 76 7912% 20 23 25 28 30 33 36 38 41 44 46 49 52 54 57 60 62 65 67 70 73 75 7813% 20 22 25 27 30 33 35 38 40 43 46 48 51 54 56 59 61 64 67 69 72 74 7714% 19 22 24 27 30 32 35 37 40 42 45 48 50 53 55 58 61 63 66 68 71 73 7615% 19 21 24 27 29 32 34 37 39 42 44 47 50 52 55 57 60 62 65 67 70 72 7516% 19 21 24 26 29 31 34 36 39 41 44 46 49 51 54 56 59 61 64 66 69 71 7417% 18 21 23 26 28 31 33 36 38 41 43 46 48 51 53 56 58 61 63 66 68 71 7318% 18 20 23 25 28 30 33 35 38 40 42 45 47 50 52 55 57 60 62 65 67 70 7219% 18 20 22 25 27 30 32 35 37 39 42 44 47 49 52 54 56 59 61 64 66 69 7120% 17 20 22 24 27 29 32 34 36 39 41 44 46 48 51 53 56 58 60 63 65 68 70

Fraction Depth ImperialHe 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300

10% 69 78 87 96 105 114 123 132 141 150 159 168 177 186 195 204 213 222 231 240 249 258 26711% 68 76 85 94 103 112 121 130 139 148 157 165 174 183 192 201 210 219 228 237 246 254 26312% 66 75 84 93 102 110 119 128 137 146 154 163 172 181 190 198 207 216 225 234 242 251 26013% 65 74 83 91 100 109 118 126 135 144 152 161 170 178 187 196 205 213 222 231 239 248 25714% 64 73 81 90 99 107 116 124 133 142 150 159 167 176 185 193 202 210 219 228 236 245 25315% 63 72 80 89 97 106 114 123 131 140 148 157 165 174 182 191 199 208 216 225 233 242 25016% 62 70 79 87 96 104 112 121 129 138 146 154 163 171 180 188 196 205 213 222 230 238 24717% 61 69 77 86 94 102 111 119 127 135 144 152 160 169 177 185 194 202 210 218 227 235 243

TRIMIX EQUIVALENT NARCOTIC DEPTH TABLE – IMPERIAL


• What is the maximum tolerable narcosis for the dive and mis-

sion? (Recommended general maximum END is 40 metres/

130 feet; the highest accepted maximums are

50 metres/165 feet for open water in good conditions, and

40 metres/130 feet for complex dives and overhead environments.

In many areas it is common to use a maximum of 30 metres/

100 feet because it doesn’t require much more helium.)

b. Oxygen exposure

• What is the bottom oxygen partial pressure?

• What are the total CNS “clock” and OTU exposures for the entire

dive?

c. Decompression issues

• What will the decompression duration be? Is that a thermal con-

sideration?

• Is there ample gas for the decompression and reasonably possi-

ble contingencies?

d. Logistics

• What gases are available?

• Do some gas blends have substantial advantages (available pre-

mixed to save time/cost, tables already prepared for specific

blends, etc.)?

• What is best for the team in choosing compatible mixes?

6. The “ideal” trimix is defined as the trimix that has an oxygen percent-

age that yields a PO2 of 1.4 and an END of 40 metres/130 feet at the

planned depth. For a given set of deco gases it is the trimix with the

theoretically shortest decompression for that depth based on using

the highest possible oxygen content and the lowest possible helium

content.

a. You can find the ideal by using the Maximum Depth Table and the

Equivalent Narcotic Depth table (metric or imperial).

• On the Maximum Depth Table, follow the 1.4 column to the

desired depth, or next greater depth if the exact depth isn’t list-

ed; follow the row left to the oxygen percentage in the right col-

umn. This tells you the oxygen the blend should have.

• On the Equivalent Narcotic Depth Table, follow the depth column

for the planned depth to 40 metres/130 feet or the next shallower

depth if 40 metres/130 feet isn’t listed, then follow the row left to

the helium percentage in the right column.

– EXAMPLE: What is the ideal trimix for 64 metres/210 feet?

– In the Maximum Depth Table, in the 1.4 column find

64 metres/210 feet. Go left to find 19 percent.

– Find the 66 metre (rounding up from 64)/210 foot depth col-

umn on the Equivalent Narcotic Depth Table, and follow it

padi.com 3-49


down to 40 metres/130 feet. Go left to find 34 percent (met-

ric)/33 percent (imperial) helium (slight difference due to

rounding in metric)

– The ideal trimix would therefore be TMx19/34 metric/TMx19/33

imperial

– You can also use a calculator to find the ideal mix.

b. The ideal trimix is often not ideal.

• Doesn’t consider oxygen exposure – may be useful to have less

oxygen to minimize CNS “clock” and OTUs, especially when mak-

ing repetitive dives or multiday dives. Better to deco longer than

to push your oxygen limits.

• Mission may call for more conservative narcotic limit of 30 metres/

100 feet END or shallower.

• Ideal trimix is seldom a blend that divers commonly use.

7. Hypoxic trimix

a. “Hypoxic” means “low oxygen.”

b. “Hypoxic trimix” means a trimix with less than 21 percent oxygen,

with 18 percent the recommended minimum for use at the surface.

As low as 16 percent can be breathed at the surface.

• Trimix with as little as 10.5 percent oxygen is common for deeper

exploration, especially in the 90 metre/300 foot range.

• Although the blend may have insufficient oxygen PO2 to breathe at

the surface, it will at depth due to increased partial pressure of

oxygen.

c. Hypoxic trimix is used to reduce oxygen exposure on deeper dives.

d. You may need a travel gas, which is simply a higher oxygen mix that

you use until reaching a depth deep enough to use the trimix.

• Failure to use a travel gas can cause you to lose consciousness

without warning due to hypoxia.

• You use a travel gas at least until you reach a depth at which you

have a PO2 of .16 ata or greater with bottom gas. (Use the Trimix

Oxygen Management Table to determine how deep you have to

descend to reach a PO2 of .16 ata or greater).

– EXAMPLE: Using TMx 14/33, how deep do you have to descend

for a PO2 of .16 ata or greater? On the 14 percent Trimix Oxygen

Management Table, follow the oxygen partial pressure column

down until you find the first PO2 of .16 or higher, in this case

.18. Follow the row left to find 3 metres/10 feet. You would use

travel gas until reaching 3 metres/10 feet.

• Community practice is to use some of the lowest oxygen deco gas

(consumption included in gas planning), especially when descent

is direct and short.

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– In previous example, use EANx36 or other deco gas until you

pass 3 metres/10 feet.

• Travel gas may be an intermediate depth trimix or enriched air

nitrox.

– Common when you have a long descent or a long swim at an

intermediate depth before descending to the bottom depth.

– Use of intermediate travel gas can reduce deco time by allow-

ing higher oxygen content for long intermediate level.

– EXAMPLE: Dive planned on a wreck to 69 metres/230 feet for

25 minutes bottom time using TMx14/40. However, you plan

10 minutes of the bottom time swimming along the upper hull

at 30 metres/100 feet before descending to the bottom depth,

so you use EANx32 from the surface until you descend from

30 metres/100 feet (not an isobaric counterdiffusion issue

because you continue descent).

• Travel gas may be used as a decompression gas, especially for

some of the deep stops (more about deep stops shortly)

– EXAMPLE: Dive planned to 75 metres/245 feet using TMx11/50

for 25 minutes. You have to use travel gas to 5 metres/15 feet

and you need the extra gas volume, so

you take TMx21/15 and use it to 48

metres/160 feet. On ascent, you use it

beginning with your second deep stop

at 42 metres/140 feet until switching to

EANx36 at 33 metres/110 feet.

– In the above example, note that the use

of “thin” TMx as a travel gas allows you

to stay on the higher O2 blend deeper

than if using air.

• Remember that if you need a travel gas on

the way down, you will need it on the way

backup. You will also need it for any

breathing at the surface (waiting for the

boat, etc.)

– Your back gas becomes unavailable on ascent at the depth you

needed your travel gas to reach on the way down.

– Back gas may be breathable for much of your decompression,

but you need to be aware of when you’re too shallow to use it

in an emergency.

– Even 10 percent oxygen gas is breathable as shallow as

6 metres/20 feet, so this is primarily an issue for the 5 metre/

15 foot and shallower stops with less than 10 percent oxygen

(blends this low in oxygen not likely needed for new trimix

divers).

padi.com 3-51


• Handle travel gas like any other stage/deco gas with respect to

NO TOX switches.

• You cannot go to back gas between switches when above your

back gas minimum depth, so you go to travel gas between deco

cylinders.

• If you expect a high exertion level, or you’re diving at altitude, 16

to 18 percent oxygen may be too low to use at the surface. In that

case, you might use a travel gas with 21 percent or more oxygen

at the surface.

e. As you recall from the Tec Deep Diver course, if you experience any

CNS oxygen toxicity symptoms, your first option is to switch to a

low oxygen gas to lower your PO2.

– Typically this is your back gas but use caution with a hypoxic

trimix.

– Assuming proper gas switches and staying on back gas at your

deep stops (more about these next), CNS oxygen toxicity is

most likely at shallow depths near the end of the dive with

your high oxygen deco gases.

– A hypoxic trimix back gas may not have enough oxygen if

you’re too shallow, such as at 5 metres/15 feet or shallower

using TMx10.5/50. You would need to switch to your travel gas

or lowest oxygen deco gas.

– With 14 percent or more oxygen in your back gas, you can use

back gas shallow as 3 metres/10 feet. As a beginning trimix

diver staying within the depth limits of this course (75 metres/

245 feet), you should seldom if ever need less than 16 percent

oxygen in your back gas.

8. Repetitive dive gas.

a. Some environments do make it feasible to make a repetitive dive.

b. You should make repetitive dives to the same or a shallower depth,

so your oxygen content can usually be the same or higher (if shal-

lower).

c. Helium content should be appropriate for the depth.

d. Many decompression experts recommend that you do not follow a

trimix dive with a repetitive dive that uses air or enriched air as the

bottom gas. Although the concerns are theoretical and not univer-

sally agreed upon, this is the conservative approach.

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C. Decompression II – Deep Decompression Stops, Air Breaks, Deco Gases

and Ascents



1. What is a deep stop?

2. What information supports the use of deep stops in trimix

diving?

3. What are three ways that you determine deep stops using

desktop deco software?

4. What are two ways to determine deep stops using a multigas

trimix dive computer that does not calculate deep stops?

5. As a general rule, what gas should you use at your first deep

stop and why?

6. What are air breaks? Why and how should you do them?

7. What are the most common decompression gases for trimix

diving?

8. Why is there some theoretical benefit to having a small percent-

age of helium in some of your deco gases?

9. What is the optimum way to ascend when making a trimix

decompression dive?

1. As you learned in the Tec Deep Diver course and as mentioned earlier,

deep stops have become common practice in tec decompression

diving.

a. Deep stops are stops for

one to five minutes (one or

two min most common)

between the bottom and

the first deco stop

predicted by most comput-

ers/software running a

neo-Haldanean model

(Buhlmann most common).

b. As noted previously, some

desktop deco software can

be set to put in deep stops.

2. Deep stops have not been

tested formally to any great

extent, but field experience

and theory support using

them, and they’re becoming more common.

a. Divers using deep stops report feeling less fatigued after a long

deco dive, which is attributed to less decompression stress.

b. Deep stops are used widely (depending on location), and there

have been no indications that they cause a problem.

padi.com 3-53


c. Bubble dynamics models all predict a benefit to making decompres-

sion stops deeper. The deep stops procedure is consistent with

these models.

3. With your desktop deco software, you can calculate deep stops three

ways.

a. Automatic deep stops – set the software to generate them; the deep

stops are generally indicated differently.

b. Use a bubble dynamics model if part of your desktop deco software.

• These are technically not “deep stops” but a model that begins

decompression deeper than modified neo-Haldanean models like

the Buhlmann model.

• Note that bubble dynamics models have less field experience and

predict shorter deco schedules than the neo-Haldanean models.

• Most conservative approach is to use deep stops with a neo-

Haldanean model.

c. Determine the deep stops and insert them as waypoints if your

desktop deco software does not generate them automatically.

• The first deep stop is the approximate halfway point between the

bottom and the first required stop.

• In trimix diving, it’s common to use

multiple deep stops because you’re

frequently ascending from a deeper

depth and have a longer decompres-

sion compared to tec diving with

air/enriched air.

• Each successive deep stop is the next

halfway point between the current

deep stop and the first required stop,

until reaching a stop that’s approxi-

mately 3 metres/10 feet deeper than

the first required stop.

• Deep stops should be entered into

your deco software (to cover gas

requirements and oxygen exposure as

well as deco considerations).

• Deep stops are typically one to five minutes, with one-two min-

utes most common. Be sure to enter the planned duration into

your desktop deco software and decompress accordingly because

deep stops may affect shallower stops.

• To find the deep stop depth (halfway point), subtract the first

required stop depth from the bottom or previous stop depth.

Divide this by two and subtract it from the bottom or previous

stop depth. If the answer isn’t a standard stop depth, it’s typical,

3-54 padi.com


but not essential, to round to the next deeper stop in 3 metre/10

foot increments: e.g. round 68 metres to 69, or 155 feet to 160

• You can also use the Deep Stop Calculation Table – find the bot-

tom or previous stop depth on the left and the first required stop

depth at the top. Round to next greater depth if exact depth not

shown. Where the two intersect find the halfway point. If not on a

typical 3 metres/10 foot stop increment, you may (but it’s not

essential) round to the next deeper 3 metre/10 foot increment

stop depth.

• EXAMPLE (based on table and rounding to next deeper 3 metre/

10 foot increment stop depth): You’re ascending from 60 metres/

200 feet. Your first required stop is at 9 metres/30 feet. What are

your deep stops?

– First deep stop is approximately 35 metres/115 feet (midpoint

between 60 metres/200 feet and 9 metres/30 feet).

– Second deep stop is 23 metres/75 feet (midpoint from

35 metres/115 feet, rounded to 36 metres/120 feet on table, and

9 metres/30 feet).

– Third deep stop is

17 metres/ 55 feet (round-

ed to 18 metres/60 feet).

– Fourth deep stop is

14 metres/ 45 feet (round-

ed to 15 metres/ 50 feet).

4. If using a multigas trimix comput-

er that doesn’t provide deep

stops, despite your preplanning

with desktop deco software, you

may have to determine deep stops

on the fly. This is because your

computer follows your actual pro-

file, and you may be ascending

from an actual bottom depth

slightly deeper (contingency situation) or shallower (multilevel pro-

file) than planned.

a. The first option is to calculate the stops in your head as described

before by subtracting your present depth (bottom or current deep

stop) from the first required stop shown by your dive computer,

dividing by two and subtracting that from your current depth. This

works, but is obviously not recommended.

b. A simpler procedure is to determine the stops with the Deep Stops

Calculation Table slate (as previously described) based on your cur-

rent depth (bottom or deep stop), and the first required stop shown

by your computer.

padi.com 3-55


c. Either way, you may round to the next deeper 3 metre/10 foot incre-

ment stop depth on the table, though this is optional.

d. The dive computer will automatically calculate your deep stops into

your decompression requirements.

5. Generally, you make your deep stops using back gas (your lowest

oxygen gas).

a. This helps oxygen exposure by reducing your PO2, which is general-

ly near 1.4 ata on the bottom.

b. Your first stop after a gas switch often puts your PO2 up to 1.6 ata,

so it’s wise to keep your oxygen exposure lower as long as possible

– the big depth change will be creating a decompression benefit

without raising oxygen. (Note that you can reduce your oxygen

exposure by planning gas switches for the depth at which the gas

has a 1.4 ata PO2.)

c. On some dives, your deep stops may be deep enough that you want

to stay on trimix to manage narcosis.

d. Even if a trimix travel gas or breathable deco gas (PO2 below 1.6

ata) is available, it is typically recommended to stay on lower oxy-

gen back gas until reaching a deep stop shallow enough for the trav-

el gas PO2 to be less than 1.4 ata or lower. This keeps oxygen expo-

sure low immediately following the deep portion of the dive.

e. May be possible to plan a deep stop as an extended second level of

a multilevel profile for more time on task.

6. Air breaks

a. As you learned in the Tec Deep Diver course, an air break is a break

from high oxygen deco gases to air (or lowest oxygen gas available)

for five minutes each 20 to 25 minutes maximum.

• reduces risk of CNS toxicity

• does not count as deco time on

an accelerated decompression

schedule

• switch multigas computers to

the break gas

• some desktop deco software

will automatically add air

breaks

• air breaks more frequently are

fine – some theory suggests

breaking more frequently makes

deco a bit more effective by

reducing oxidative stress on the

lungs to maintain optimum gas

exchange; many divers opt to break for two to five minutes each

10 to 12, which is fine.

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• 20 to 25 minutes is the maximum without a break, but more fre-

quent may be better

b. Total oxygen exposure is typically higher on a trimix dive due to

decompression time, so air breaks are even more important. To

manage oxygen exposure, it’s best to keep your PO2 on the low side

during the deep portion of the dive so you have adequate exposure

margin during decompression.

c. When diving air/enriched air, the break gas is always the lowest oxy-

gen gas (back gas), but this is not necessarily true with trimix.

• switching to trimix with a high helium content late in the dive

poses some theoretical risk of isobaric counterdiffusion, though

in practice this has not been a major issue

• the lowest oxygen deco gas without helium or with very low heli-

um may therefore be the appropriate choice

• there are varying opinions on this – be conservative

d. Based on bubble dynamics models, there’s a growing practice of

having some helium in the break gas. Thus, it may be appropriate to

break with a travel or deco gas trimix with five to 20 percent helium

(and least oxygen available). More about helium in deco gases

shortly.

• Use of helium in the break gas/deco gas varies somewhat interna-

tionally.

• The practice is most common with the more serious trimix dives

with longer decompression requirements.

e. Air breaks do not count as deco time when following a dive table

unless you entered them, with the appropriate gas, into your deco

software.

f. Air breaks count as deco time with multigas trimix computers –

switch on the fly to the break gas during the air break and the com-

puter adjusts your deco schedule accordingly.

7. Deco gases

a. As you know, practically speaking, trimix diving requires accelerat-

ed decompression.

b. The practice is to NO TOX switch to higher oxygen, low helium

gases as soon as possible to speed elimination of helium and

nitrogen.

• As a reminder, your PO2 should not exceed 1.6 ata while decom-

pressing.

• In planning your oxygen exposure, you can often greatly reduce

your OTUs and CNS clock by keeping the PO2 even lower as

much as possible while not significantly increasing your decom-

pression.

• To manage oxygen exposure, the first deep stop and commonly

the first two or three, are made with back gas to keep the oxygen

padi.com 3-57


exposure low following the higher oxygen exposure at the bottom

depth.

• EXAMPLE: Suppose you dive to 90 metres/300 feet using TMx14/50.

Your bottom PO2 is the maximum allowable 1.4 ata (not recom-

mended that you push limits; but to make a clear example).

Assuming your first deep stop is 70 metres/230 feet, staying on

TMx14/50 your PO2 falls to 1.1 ata., providing an oxygen exposure

break. If you switched to a travel/deco gas of TMx20/45, you’d

spike your PO2 to 1.6 ata., increasing your CNS toxicity risk.

c. The most common deco gases are:

• 100 percent oxygen from 6 metres/20 feet to the surface (recall

that it’s typical to make 6 metres/ 20 feet the last stop, or 5 me-

tres/15 feet if necessary to control oxygen exposure), EANx50

from 21 metres/70 feet and EANx36 from 33 metres/110 feet

• EANx32 and air sometimes used.

• In some areas, EANx80 and EANx40 are the common choices in

place of oxygen and EANx50, respectively.

• Other variations of EANx may be used if neces-

sary, of course, due to availability, logistics, etc.

• Remember that oxygen content is the primary

factor in a blend’s deco efficiency.

• Just because three or four deco gases are avail-

able doesn’t mean that’s the best dive plan – the

simplicity of two deco cylinders may be better.

d. Based on bubble dynamics theory, there’s a growing

trend of decompressing with five to as high as 20

percent helium in the deco gases (except for the

final stop on 100 percent oxygen).

• Because helium diffuses rapidly, the theory is that

a small amount of helium reduces helium’s off

gassing gradient in the lungs. This slows the

speed at which the pressure of the helium dis-

solved in the blood drops. This theoretically cre-

ates a lesser gradient between the tissues and the

blood, thereby reducing potential bubble forma-

tion during offgassing. Because of helium’s rapid

diffusion, it still leaves the body quickly compared

to nitrogen. The fewer bubbles, the more efficient

and effective the decompression is as well (theo-

retically).

• Helium in the deco gases may be important on

extreme dives where deco begins deep, to offset

narcosis and ease breathing resistance.

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• Isobaric counterdiffusion is not a substantial issue with this little

helium in the deco gas (the potential rises with the fraction of

helium, but doesn’t appear to be an issue with the low percent-

ages being used for this purpose).

• The typical deco gases correspond to the traditional EANx blends

with respect to oxygen content, such as TMx36/10, TMx50/10, etc.

• The benefits are largely theoretical, but it is becoming a common

practice with widespread anecodotal success, with no risks or

negative issues reported at this writing.

• In programming a multigas trimix computer or writing tables with

desktop deco software, you enter the appropriate trimix as the

deco gas so the deco algorithm accounts for the helium in the

deco schedule. Addition of helium slightly increases the deco

requirements with most models.

• Because helium in deco gases can significantly increase dive cost

(helium costs vary widely), in some areas helium in the deco

gases isn’t common on dives with relatively short decompression

obligations.

• You can also keep helium in your decompression by using deco

for stops shallower than you otherwise might. For instance, you

may plan to deco with EANx32 and EANx80; you can switch to the

EANx32 at 40 metres/130 feet, but instead, you plan your decom-

pression so you don’t switch until you reach 21 metres/70 feet.

This allows you to deco with helium longer, usually with minimal

extra hang time required.

e. In all cases, it’s important to balance the advantages and disadvan-

tages of different deco gas choices.

• To avoid high PO2s and high oxygen exposure (especially

multiday and repetitive diving), it may be wise to start each deco

gas use from slightly shallower (e.g., use EANx50 starting at

18 metres/60 feet instead of at 21 metres/70 feet)

• On shorter/shallower dives with only one or two deco gases, you

may want lower oxygen deco gas or gases so you can begin effi-

cient decompression deeper. (E.g. Instead of oxygen and EANx50,

you might want oxygen and EANx36 so you switch off the bottom

gas deeper for more efficient deco.)

• Desktop deco software allows you to easily compare the pros and

cons of differing gas combinations.

8. Ascents

a. You learned in the Tec Deep Diver course that ascents should be

gradual, controlled and within the prescribed ascent rate of the

deco model you’re using (generally not faster than 10 mpm/30 fpm).

b. Use your gauges to assist with your ascent rate – watch your time

padi.com 3-59


and track how fast you pass each 3 metres/10 feet. If you get ahead,

stop to allow the time to catch up.

c. Many divers stop or slow at each 3 metres/10 feet to keep their rate

in control.

d. Make deep stops a habitual part of ascents, even if not prescribed

by your desktop deco software or dive computer. Evidence increas-

ingly supports their benefit (enter them as waypoints in your deco

software).

e. It’s better to not skip stop depths even if a multigas computer or a

desktop deco table allows it – take a minute or so at each 3 metres/

10 feet (write them in as waypoints on deco software). E.g. After a

six minute stop at

18 metres/60 feet on

EANx50, the deco

software says you

can ascend directly

to 6 metres/20 feet.

Instead, enter and

make a one minute

stop for each

3 metre/10 foot stop

to 6 metres/20 feet.

f. Don’t neglect the

final part of your

ascent. The last

part creates the

biggest gas volume

changes. Go up slowly – take an entire minute or longer to ascend

the final 5 metres/15 feet. If you’ve decompressed properly this

shouldn’t be essential (so you can hurry in an emergency, for

instance), but it should reduce your risk by minimizing bubble for-

mation. Follow this with your surface deco stop.

g. With many stops in the profile, team work and communication are

essential, especially when ascending with a lift bag (teammates

monitor depth so reel diver can concentrate on depth control and

the reel).

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D. Techniques and Procedures II – Travel gas handling



1. Where do you wear travel gas when using it?

2. What is the procedure for beginning a dive on travel gas?

1. When using travel gas, you need to follow procedures

a. to avoid using back gas during descent and blacking out from

hypoxia.

b. to avoid failing to switch to back gas at depth and risking CNS

oxygen toxicity.

2. Whether you wear stage deco cylinders all left or right/left, travel gas

is normally upper (if wearing two on that side) left cylinder, the lowest

oxygen gas.

a. may be separate travel gas or lowest oxygen deco gas

3. You and your teammates begin dive by confirming for each other

that you’re breathing correct travel gas.

a. When diving with a hypoxic bottom mix, it’s a good idea to clip your

primary second stage as soon as you’re geared up so you can’t

instinctively stick it in your mouth at the start of the dive.

b. If conditions are rough, you may enter water with travel gas already

secured so you can breathe from it at the surface.

4. After teammates confirm that everyone’s

breathing travel gas, dive begins.

5. At depth, team switches to back gas together

at predetermined depth (part of dive plan).

a. commonly combined with descent check

b. if staging deco cylinders, switch to back gas

commonly made when you stage cylinder

c. entire team switches together and confirms

that all have gone off travel gas and on to

back gas

6. If travel gas will be used for decompression, during ascent it is treated

as any other deco gas (handling, NO TOX switches, etc.)

7. If isobaric counterdiffusion or ascending above a hypoxic trimix’s

usable depth are possible issues, you go to your travel gas instead of

your back gas between cylinders when NO TOX switching.

E. Emergency Procedures II – Lost deco gases and computer failure



1. What are your options if you lose your decompression gases on

a trimix dive?

2. How do you handle a failure of your multigas trimix computer

during a dive?

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1. Loss of decompression gases

a. As you learned in the Tec Deep Diver course, loss of deco gases

greatly limits your options and the emphasis must be on prevention.

• In many air/enriched air tec diving scenarios, you may have suffi-

cient back gas to decompress even without deco gases. This is

very unlikely in trimix diving.

• Never stage your deco cylinders if you have any real doubts about

being able to return to them, find them or anything else that

would prevent retrieval.

• Don’t rely exclusively on deco gases supplied by a dive boat; that

may be your preferred option, but you should have the gases you

need with you. The advantage of boat-supplied gas should be that

you don’t have to refill your carried bottles after each dive.

b. In the event you lose your deco gases on a trimix dive:

• Your best option is to have support divers bring down the gases

you need.

• If you have no support divers, or they

don’t have the gases, you may be able

to deco with your teammate’s reserves

as they finish with each cylinder. This

assumes they didn’t lose theirs, too.

You’ll finish deco later, since you’ll

have to wait for them to finish decoing

first.

• If there’s no decompression gas, deco

as long as you can as best you can

using your back gas. Trimix is very

inefficient, so it’s likely you’ll not

decompress sufficiently. However, the

more you decompress, the less severe

DCS is likely to be (but there are no guarantees).

c. Again, the emphasis is on prevention. There’s nothing wrong with

wearing your deco cylinders for the entire dive.

2. Multigas trimix computer failure

a. The simplest option is to complete the dive using your backup

multigas trimix computer.

b. If you don’t have a multigas trimix computer, decompress following

your backup tables with a depth gauge and bottom timer.

c. Use the following steps to enter your backup tables after a computer

failure during decompression.

• Find the contingency table for the time and maximum depth of

your dive.

• Find the decompression stop depth at which your computer

failed. Complete the time indicated by the table.

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• Finish your decompression following the table’s stop times.

• EXAMPLE: You’ve made a dive to 73 metres/240 feet for 18 min-

utes bottom time, but your actual profile is a gradual ascent

over a rising bottom so you started your direct ascent from

about 60 metres/200 feet. You decompress with your multigas

trimix computer, which requires

considerably less time than your

73 metres/240 feet for 18 minute

backup table. At the 12 metre/

40 foot stop, your computer fails.

You find the 73 metres/240 feet for

18 minutes schedule and complete

the time indicated by your tables

for 12 metres/40 feet. Complete

decompression according to the

table’s remaining stops.

F. Team Diving II – Safety/support divers

Learning Objectives: By the end of this

section, you should be able to answer

these questions:

1. What are the roles of a support diver on a trimix dive?

2. Why are support divers especially beneficial on a trimix dive?

3. What characteristics does an effective support diver have?

1. In the Tec Deep Diver course, you learned the duties of a support

diver. Some of these take on added advantages when trimix diving.

a. Checking on divers and assuring they have ample gas, etc.

• This is especially beneficial on a trimix dive because lost or

inadequate deco gas likely means insufficient gas to decom-

press adequately. The ability to bring down deco gas can

literally be life saving.

b. Shuttling gear by taking up exhausted cylinders, unneeded gear,

etc.

• Because trimix dives commonly employ more cylinders than

air/enriched air tec dives, this can be especially helpful .

c. Watching for and locating divers separated from their teams.

Notifying teams that missing divers are located.

d. “Baby-sitting” – hovering near decoing divers to be ready to

assist.

• With longer deco times typical, this is especially reassuring.

• Confirming gas switches, tables and runtimes allows you to

anticipate needs for extra gas, etc.

e. Sitting standby on the boat or shore, fully geared up or ready to

gear up, ready to go in to assist in an emergency.

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• If this support requires going to deep depth, support divers need to

be qualified and equipped for the depth.

• Standing by in the water (baby-sitting) is more common, but surface

standby may be advantageous when exposure is an issue (tempera-

ture, etc.) and the support diver should be fresh and ready to go.

f. Shuttling communications

between the divers and

surface support.

2. The characteristics needed

of a support diver depend

upon the dive requirements,

but generally include:

a. Qualified for the support

dive and depths

• a skilled recreational

diver can handle tasks

typically needed during

the upper decompres-

sion levels

• a Tec Trimix Diver may

be needed for deeper deco levels

• especially complex missions require greater qualification, such as

trimix and cave certification for support of long distance deep cave

dives

b. Good communicator

c. Creative problem solver – able to take care of what a diver needs

d. Patient – needs to be able to hang out and watch divers deco without

getting bored.

3. Support divers stay out of decompression, except on highly complex

dives where it’s planned for – in which case, the decoing support divers

may need support divers.

a. some groups distinguish between set up divers, whose mission sup-

ports another mission (such as staging in cylinders for exploratory

divers), from support divers, who aid returning divers during decom-

pression

G. Thinking Like a Trimix Diver II

Learning Objectives: By the end of this section, you should be able to

answer these questions:

1. Why does becoming a trimix diver put you in a position of dis-

tinction in the dive community?

2. What four responsibilities do you have in that role?

1. Whether you want it or not, becoming a Tec Trimix Diver sets you apart

in the dive community.

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a. As a new trimix diver, you will be “at the bottom of the top,” one of

the less-than-one-percent of divers qualified to dive in the sport’s

deepest ranges.

b. You will be among those who accept the sport’s greatest potential

risks.

c. Your level of expertise with respect to dive skill and knowledge will

be expected to be almost professional.

2. This distinction comes with responsibilities. These include:

a. Being a role model for other tec divers and recreational divers by

respecting and following all the rules and procedures for whatever

type of diving you’re doing.

• By now you know that these exist for safety. Disregarding them or

lip service is the mark of an amateur, not a Tec Trimix Diver.

b. Showing humility.

• Being a trimix diver is an accomplishment, but keep it in perspec-

tive. It’s diving deep, but it’s still just diving.

• Diving is a diverse, broad and evolving discipline. No one knows

everything about it and no one can; it reflects poorly on those

who think and act like they do.

• Don’t present your opinion or the opinion of someone else as

fact. In tec diving as in most things, there’s usually more than one

right way to do something. Be open minded so you can continue

to learn.

• Remember and understand where we’ve come from as a commu-

nity – it helps us see where we’re going.

c. Bringing up less experienced tec divers.

• It took other divers giving you a chance

as a teammate and student to get where

you are today. Do the same for those

coming up the ranks behind you.

• Pass your experiences on to the less

experienced. Chances are, you’ve avoided

mistakes because others who didn’t told

you about them.

d. Staying current.

• Much of what you know today will be obsolete tomorrow. Keep

informed about the latest advances in dive technology, safety,

medicine, decompression and procedures.

• Dive frequently to keep your skills proficient. If you’ve not been

diving in awhile, get in the water and refresh your skills before a

“big” dive.

• Develop a reference library and information sources you can

draw on.

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VIII. Practical Application Two

Practical Application Two has four primary purposes: 1) to formalize stu-

dent practice in analyzing trimix, 2) to further team building among the

student divers, 3) to continue developing student fluency with desktop

deco software, and 4) to build upon mission planning skills learned in the

Tec Deep Diver course.

To successfully complete this Practical Application, the student will

be able to:

1. Demonstrate the use of oxygen and (if available) helium analyzers

to determine the contents of trimix blends.

2. Working as a team and using desktop deco software, plan two trim-

ix dives, both with deep stops, one requiring a travel gas and three

deco gases and one requiring three or four deco gases but no travel

gas. The plans must include gas consumption, oxygen exposure,

decompression schedules, turn pressures and contingency decom-

pression schedules for each team member.

A. Trimix Analysis

1. Provide the class with two or more cylinders of trimix.

a. Working in teams, students each take turns using an oxygen analyz-

er to analyze the contents of all cylinders. Each cylinder should be

marked with the target blend.

b. Students should be able to tell you the oxygen content of each

cylinder, tell you whether the content is close enough to the target

blend to use as that blend, and what to do if not.

c. If available, have student divers also analyze the blends using a heli-

um analyzer.

• A point of discussion: the oxygen may be dead on, but the helium

may be off anyway. Does this lead to a serious dive planning con-

cern?

– Use desktop deco to compare deco profiles and ENDs.

– (Conclusion — if the oxygen content is accurate, the variation in

helium should not be sufficient to make a meaningful difference

in dive planning.)

• Give students a trimix cylinder without the target blend indicat-

ed. Ask them to determine the trimix with only the oxygen ana-

lyzer.

– They can’t — requires a helium analyzer.

– Ask them if they can even determine if it contains helium at all.

(Yes, but not with an oxygen analyzer — take a few breaths of it

and then talk; the helium speech distortion confirms helium.)

– Remind them, “When in doubt, throw it out!” If you can’t tell the

helium and nitrogen content, you can’t plan your decompression

or narcotic depth.

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B. Dive Planning

1. Divide student divers into teams. Ideally, these should be the teams

that will dive together in Training Dive Two.

2. Assign students two dives to plan. Provide them with the simulated

depth and time to plan based on the following.

a. The first dive should require a travel gas and deco gases. It is rec-

ommended that you assign a travel gas and two deco gases. This may

be the plan for the simulated trimix dive in Training Dive Two. You

may allow student divers to determine what the gases would be, and

the travel gas may be one of the deco gases (with the volume used on

descent considered in planning. See Training Dive Two for more

details. The actual dive will be an air/enriched air decompression

dive no deeper than 50 metres/165 feet, with actual decompression

gases but the bottom gas air/EANx simulated as trimix; the class will

decompress following the trimix schedule.)

Depending upon the planned actual dive depth

and bottom time, you may assign a deeper sim-

ulated depth and bottom time or use the actual

depth and bottom time. (See Training Dive Two

for more details.)

b. The second dive planned should require a

travel gas and three deco gases. It is recom-

mended that you assign three deco gases. The

travel gas may be one of the deco gases with

the volume planned accordingly.

c. Both dive plans must include:

• deep stops. If the software doesn’t generate

them, then students enter them manually as waypoints.

• gas supply requirements for each diver based on personal SAC

rates

• decompression schedule with runtime

• turn pressures

• contingency (bail out) decompression schedules

• oxygen exposure (OTUs and “CNS clock”)

3. After teams complete the desktop deco software planning and suc-

cessfully fulfill the required criteria, assign them a mission to plan in

Training Dive Two within the planned limits.

a. The mission is within your discretion, and may be based on the envi-

ronment and other local variables.

b. Choose something complex enough that it requires forethought and

teamwork, but simple enough to accomplish within the context of

learning new trimix skills and procedures. This could include:

• lay down a four equal-sized box grid using line

• measure something (reef section, wreck feature, etc.)

padi.com 3-67


• attach a lifting device to something with three different knots

required (but the actual lift is not made)

c. If the mission duration would be longer than available bottom time,

check that team revises plan to accommodate actual dive time.

d. Remind student divers that completing the mission is not the pri-

ority; completing the dive safely as planned is the priority.

4. Training Dive Two is optional for Tec Deep Diver certified students

who were certified in the previous six months or who have made at

least one technical decompression dive requiring a decompression

cylinder to 40 metres/130 feet or deeper in the previous six months,

but they must complete the planning practical application whether

they will actually make the dive or not.

IX. Training Dive Two

To successfully complete this training dive, the student will be

able to:





procedures.

2. Working in a team, plan and execute a simulated trimix accel-

erated decompression dive using a table and/or multigas com-

puter using air/enriched air as the bottom gas, and air,

enriched air and/or oxygen for decompression gases. The dive

will be an actual decompression dive,

but will follow a trimix decompression

schedule.

3. Deploy a lift bag from the bottom as a

team and ascend along the lift bag line

following the decompression schedule.

4. Working as part of a team, respond

appropriately to spontaneous simulated

emergencies presented by the instructor

throughout the dive.

5. Monitor and record depth, time and gas

supply information during decompression

to determine the deco SAC rate.

6. Working as a team, attempt to complete a

dive mission assigned by the instructor.





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TRAINING DIVE TWO

• Entry • Descent

• Descent check.

• Dive mission

• Lift bag deployment and ascent

• Exit POST DIVE• Performance review• Divers disassemble and stow their

gear as appropriate.• Log dive for instructor signature

POST DIVE• Performance review

• Divers disassemble and stow theirgear as appropriate.

• Log dive for instructor’s signature.


A. Training Dive Two Standards

1. Training Dive Two is conducted in open water

as a decompression dive. The minimum depth is

27 metres/90 feet and the maximum depth is 50

metres/165 feet.

2. Ratios – 2 students to 1 instructor, with 1 more

student permitted with a certified assistant to a

maximum of 3. (See Section Two for specific

requirements necessary to qualify as a certified

assistant in this course.) These are maximums –

reduce ratios as necessary to accommodate stu-

dent characteristics and environmental/logistical

considerations.

3. Students and instructor must be equipped as

described in the Tec Deep Diver course, with

accommodation for environmental needs. This

includes but is not limited to:


posts.





Diver course.

c. Two stage/decompression cylinders configured as described in

the equipment requirement section, and following the rigging

philosophies described in the Tec Deep Diver course.

4. Gas requirements. Student divers and staff may use air or enriched

air, any suitable blend. These may be blends such as air, EANx 32, 36,

padi.com 3-69

Note that Training Dive Two is optional for students certified as DSAT Tec Deep

Divers who were certified in the previous six months or who have logged at least

one technical decompression dive requiring a decompression cylinder to 40

metres/130 feet or deeper in the previous six months. It is required for student divers

entering the Tec Trimix Diver course with a qualifying prerequisite certification from

another training organization. You may require Tec Deep Diver certified students to com-

plete this dive in any case at your discretion, such as to improve mastery, allow additional

learning time, or simply for added experience with slightly more depth.

Training Dive Two is recommended for any students who are not showing the pol-

ished technique expected of trimix level divers, especially maintaining a tightly controlled

decompression stop depth. Use this dive to emphasize streamlining, buoyancy control

and body position. Assign additional skills that require deploying and properly restowing

gear, with an emphasis on a clean rig before and after the drill.


50 and oxygen. It is recommended that you have students simulate

starting the dive using one of the deco gases as a travel gas, figuring

the gas consumption into their dive plans. Back gas should be a simu-

lated trimix that cannot be breathed shallower than 3 metres/10

feet, but should actually be air or enriched air and marked accord-

ingly. The decompression gases should be the actual gases called for

in the decompression schedule.

5. Decompression planning. Trimix schedules call for

more decompression than air/enriched air dives

for the same depth and time, so decompressing

according to a trimix schedule is acceptable. The

dive must be planned according to a simulated

trimix schedule that requires at least four deco

stops and two deco gases. The actual required

decompression schedule may require fewer stops

and/or deco gases. Student divers should have the

actual schedule available for ending the dive

more quickly in a contingency situation.

The simulated decompression schedule

should include deep stops, either generated by

desktop deco software automatically or determined manually and

inserted as waypoints. Deep stops that would not be possible because

the simulated depth is deeper than the actual depth may be omitted.


1. Predive briefing

a. Group in teams, students set up their rigs, analyze gases, but do not

yet don exposure suits.


• Inspect each rig for correct setup, ample gas supply, etc. Pay par-

ticular attention to proper cylinder markings written and placed

so team can read them while worn.





c. Dive overview

• Depth/time limits

• It’s recommended that you have student divers write down the

dive overview and notes on a slate for reference during the dive,




– appropriate entry, don stage/deco cylinders (at surface or

before entering water)

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– students use travel or appropriate deco gas at surface

– bubble check

– descent

– NO TOX switch to back gas at planned depth; descent check

– dive mission

– lift bag deployment

– follow trimix deco schedule with NO TOX gas switches

• Spontaneous emergencies (surprise drills). The exact emergency

and timing is left to the instructor’s discretion, but there should

be at least two unannounced emergencies per team during this

dive.

– Suggested emergencies include lift bag failure, exceeded depth

or bottom time, free flowing regulator, etc.

– Since this is an actual decompression dive, do not assign

emergencies that could compromise buoyancy control or an

effective decompression schedule, e.g., failed BCD, unrespon-

sive diver, decompressing with no reference, etc. Midwater

gas shutdowns (free flowing regulator) should follow all

required decompression.

– Inform students that the simulated emergency ends when you

signal it, and that they may discontinue the emergency drill if it

affects their ability to properly decompress or control the dive.

– Tells students to signal when they’ve completed required

decompression, but not ascend to the surface until you signal

them to (except in a real emergency, of course) so that you can

assign further emergency exercises midwater after completing

decompression.

• Time, depth and gas supply awareness –

assigned by instructor.

– May be depths, times, pressures, turn pres-

sures, etc. Goal is to get divers to constant-

ly monitor time, depth and gases.

– Instructor will not remind divers to do

this.

– Teammates are encouraged to assist each

other with this.

– Students must do this no matter what else

is going on, short of a real emergency.



dive plans.

• Remind divers they are carrying gases that they cannot safely

breathe at the bottom depth.

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Teams plan dives and gear up



they generate from a depth, trimix and at least two deco gases.

The trimix will be simulated, but the deco gases should be the

actual gases they will use. They should generate an entire plan

with deco schedule, contingency schedule, gas volume require-

ments, turn pressures and oxygen exposure for each diver. You

may have them do this by hand or use desktop deco software, or

you may have them use the schedule and plans from Practical

Application Two as appropriate. Allow ample time for proper

planning, which may take an hour or more. The final plans should

include gas volume requirements for all divers and may be pre-

sented on the TecRec Dive Planning Slate or on a computer print-

out. It’s also recommended that you have students laminate

copies of their tables to carry on the dive. (Note: Remind divers

that losing their tables is not only potentially unsafe, but environ-

mentally unfriendly.)

• Teams gear up and finish their checks with

Being Wary Reduces All Failures.

– Students use TecRec Equipment Checklist

to confirm each other’s equipment setup.

– Touch drill while geared up and seated,

students reach back and touch (grasp)

regulator and isolator valves as if to

close/open them.

– Teammates adjust equipment/assist each

other as necessary.

C. Training Dive Two – suggested sequence

1. Entry – appropriate for environment, deep water

entry recommended.


change.


tance, or prior to entering water (as appropriate for environment

and logistics).


O-rings at hand.

d. Divers use appropriate deco gas as simulated travel gas at surface.

Teammates confirm correct gas use.

2. Descent

a. Descend and stop at planned depth for switch to back gas.

b. Student divers NO TOX switch to back gas.

c. Descent check.

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BeingWary

ReducesAll Failures


d. Stage cylinders at deco levels (if appropriate to environment).

e. Continue descent to insensitive bottom.

f. Position class for skills

3. Dive skills – for each, instructor demos (if

necessary), then has students perform

a. Dive mission

• The assigned mission should be simple

and reasonably within the students’

ability to carry out.

• Completing the mission is not required

because the primary dive goal is the

dive.

• The purpose is to give student divers a

chance to practice planning and carry-

ing out missions while managing tec

diving equipment and procedures.

b. Lift bag deployment and ascent and decompression with NO TOX

gas switches

• Each team deploys lift bag. It is recommended that they ascend

along the lift bag line, following the planned trimix decompression

schedule as a neutrally buoyant hang with a fixed line or reference

available.

• Watch for proper NO TOX gas switches.

• If necessary for logistics in a current, teams may also maintain con-

tact with an anchor line or other stationary object to prevent drift-

ing.

• Student divers should not vary more than 1 metre/3 feet from the

stop depth during gas switches nor more than .6 metres/2 feet after

completing gas switch. Encourage teammates to help each other


c. Spontaneous emergencies

• At least two emergencies per team, either on the bottom or during

decompression.

• Avoid assigning emergencies that could affect buoyancy control

and an accurate decompression schedule. Assign midwater emer-

gencies that could effect stop depth after completing all required

decompression.

• Remind students that the drill ends on your signal, or if the emer-

gency procedure affects their ability to decompress effectively or

control the dive in any way.

• It is acceptable if emergency drills compromise the mission. (The

lesson is that the mission is always the lowest priority in a dive –

coming back safely is the priority.)

padi.com 3-73


• Midwater emergencies (after completing all required decompres-

sion) should focus on realistic situations and emphasize stop

depth control while handling the problem. These can include hav-

ing divers face away from the line and maintain stop depth (loss

of line) or writing the procedures they would follow for an omit-

ted deco problem while maintaining stop depth without physical

contact.

4. You may have students stage cylinders as appropriate for local dive

environment or for additional cylinder handling practice.


D. Post Dive








3. Have divers calculate and show you their swimming and decompres-

sion SAC rates based on the information gathered during the dive.

4. Confirm divers surface with 1/3 (or other planned reserve) of all

gases remaining.



X. Knowledge Development Presentation Three

A. Emergency Procedures III



1. What are the procedures for missed decompression stops when

diving with trimix?

2. What are the procedures for delays in ascents when diving

with trimix?

3. What are the procedures for omitted decompression when

diving with trimix?

4. What should you do if you experience DCS symptoms under-

water?

5. What is the recommended first aid for DCI when diving with

trimix?

6. What should you do if you experience

CNS oxygen toxicity symptoms during

a trimix dive?

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[Note: Have student divers

review their TecRec Emergency

Procedures Slate while you go

through this section.]


1. The procedures for omitted decompression, delays in ascent, DCI first

aid and oxygen toxicity are the same for trimix as you learned in the

Tec Deep Diver course.

2. If you miss a decompression stop when diving with trimix:

a. Immediately redescend, ideally in less than one minute.

• Complete the stop plus one minute.

• Decompress according to normal

schedule.

b. If unable to redescend

• Stay at the next stop for combined

time of both stops.

• Extend 6 metre/20 foot stop and

final stop by 1.5 times normal deco

time

2. If you have a delay in ascent:

a. If you have a delay before reaching

your first stop

• Add delay to bottom time and decompress on new schedule.

• Extend final stop as much as practicable, gas allowing.

b. If you have a delay between stops

• Not critical if not longer than 2-3 minutes.

• Do not count delay time as deco time.


3. If you accidentally omit decompression:

a. If you omit decompression from 6 metres/20 feet or shallower, have

no DCS symptoms and return to stop depth in less than one minute

• Complete decompression as scheduled.


b. If you omit decompression from 6 metres/20 feet or shallower, have

no DCS symptoms and return to stop depth after more than one

minute

• Extend 6 metre/20 foot stop and final stop by 1.5 times normal

deco time.

• Extend final stop as much as practicable beyond the 1.5 times

deco time, gas allowing.

c. If you omit decompression from deeper than 6 metres/20 feet and

have no DCS symptoms

• Return to stop depth as quickly as possible (less than 5 minutes

ideally).

• Decompress according to schedule up to and including 12 metre/

40 foot stop.

• Extend 9 metre/30 foot stop and all shallower stops by 1.5 times

normal deco time.

padi.com 3-75


• Extend final stop beyond 1.5 times deco time as much as practica-

ble, gas allowing.

d. Omitted decompression procedures are based on dive circum-

stances in which there is no recompression chamber immediately

available, as is typical in technical diving. If a chamber is available,

it may be appropriate to follow chamber-based procedures for omit-

ted decompression as listed in the U.S. Navy Diving Manual.

e. Remember that trimix is less forgiving than air/enriched air with

respect to omitted decompression. Emphasize prevention.

4. DCS while underwater

a. It is rare to have DCS symptoms before surfacing when diving with

air/enriched air unless large amounts of decompression have been

skipped. Trimix is more likely to cause DCS symptoms prior to sur-

facing. If it happens, it is usually at or above the 6 metre/20 foot

level.

b. If you experience DCS symptoms under-

water

• Signal your teammates and/or support

divers that you suspect DCS.

• If possible and recompression is not

immediately available, complete your

decompression.

• Extend stops 6 metres/20 feet and shal-

lower on pure oxygen (with air breaks)

while your team completes decom-

pression, surfaces, contacts emergency

medical care and prepares for your transportation to the appro-

priate medical facility. If possible, a team member should stay

with you (this may be a judgment call based on how severe your

symptoms, how much support is available and what needs to hap-

pen at the surface).

• Stay on oxygen when you surface; minimize activity and stay lying

down as much as possible – let your teammates help you get your

gear off, etc.

• Continue with first aid for DCS until reaching appropriate medical

care. Take a copy of your dive schedule with you.

5. First aid for decompression illness when diving with trimix is the same

as for any other DCI incident.

a. Keep patient lying down. On the back is fine for a responsive

patient, or left side down (recovery position) for an unresponsive

breathing patient.

b. Monitor airway, breathing and circulation. Provide CPR as neces-

sary.

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• Automated External Defibrillators (AEDs) have yet to become

common on dive boats and at dive sites because of regulations,

the recency and changes in the technology and other issues.

• However, if available, legal to use in your area and you’re trained

to use it, an AED is an excellent extra step above the community

standard of care that may be used as necessary.

c. Administer emergency oxygen, ideally 100 percent oxygen with a

demand system.

• Weak patients and nonbreathing patients (with ventilations) may

require freeflow oxygen.

• Continue oxygen until the patient reaches emergency care or until

supply exhausts (responsive patients may be able to use oxygen

from a deco cylinder, or highest oxygen available if pure oxygen

runs out)

d. Responsive patients may drink water.

e. Contact emergency medical care and the diver emergency service

(DAN, etc.) that serves the area to get the patient into medical care

and ultimately to recompression. Statistics show that the sooner

recompression begins, the more likely a favorable outcome. Having

diver insurance can also reduce delays by minimizing concerns

about financial compensation for the treating facility.

6. CNS symptoms underwater

a. If you experience CNS symptoms underwater (remember convul-

sion, VENTID), immediately switch to low oxygen gas – back gas,

travel gas or lowest oxygen deco gas – remember the concerns

involving hypoxic trimix at shallow depth.

b. Ascend as much as possible immediately

without compromising decompression.

c. Stay on low oxygen gas for at least 15 min-

utes after all symptoms subside.

d. Keep your PO2 as low as reasonably possi-

ble without compromising your ability to

complete decompression due to gas supply,

etc. (this is made more feasible with multi-

gas computers).

e. Convulsions are more likely to be fatal than

DCS; if in doubt and necessary, better to

increase your DCS risk somewhat to mini-

mize CNS oxygen toxicity risk.

f. Keep in mind that a fullface mask reduces

the risk of drowning in the case of a convul-

sion; use of full face masks compatible with

tec diving like the M-48 is becoming more common.

padi.com 3-77

B. Techniques and Procedures III – Streamlining and Breathing



1. What level of streamlining and swimming technique is expected

of a trimix diver?

2. Why does shallow breathing lead to rapid breathing and high

gas consumption?

3. In what two ways can carbon dioxide buildup affect you?

1. As a trimix diver, you’re expected to have the highest levels of equip-

ment streamling and swimming technique.

a. Have all the equipment you need, but nothing you don’t.

b. Everything should be tucked, stowed or otherwise secured so that

it’s readily accessible, yet doesn’t dangle, protrude or otherwise

interfere with clean lines (this is one reason why tec divers don’t

like instrument consoles).

c. You should swim with precision buoyancy control, remaining neu-

trally buoyant, fins high to avoid silting, and staying off the bottom.

2. Emphasize slow, deep controlled breathing.

a. Shallow breathing uses only a portion of the lungs for gas exchange.

b. Poor gas exchange causes carbon dioxide to build up, leading to the

need to breathe faster.

c. Faster breathing only partly keeps up with the body’s demands, so

your gas consumption goes up significantly.

d. This is mostly likely when you exert yourself at depth. Pay attention

to your breathing and keep it controlled at all times.

3. Carbon dioxide buildup from shallow breathing has two effects to avoid.

a. Significant increase in gas consumption as just discussed.

b. Narcosis – opinions differ whether carbon dioxide is itself narcotic,

whether it contributes to the nitrogen/oxygen narcosis mechanism

or both, but raised carbon dioxide appears to elevate narcosis, even

when using trimix.


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C. Thinking Like a Trimix Diver III



1. What four differences of diving with trimix versus diving with

air/enriched air must you consider when planning a mission?

2. How may each of these differences affect a mission plan?

3. What aspect of a trimix dive do you need to constantly remind

yourself of?

4. What is the primary mission of any dive?

1. You learned the basics for mission planning in the Tec Deep Diver

course, but using trimix versus air/enriched air has four considera-

tions that may affect mission planning.

a. Decompression duration – typically longer with trimix

• This affects gas volume requirements for deco.

• Exposure protection may be an issue.

• There may be more need for support divers.

b. Depth – often deeper with trimix

• This affects bottom gas volume requirements – may need larger

cylinders, and it’s important to control your breathing.

• Bottom time may be too short to accomplish mission on a single dive.

c. Narcosis reduction – trimix is less narcotic than air/enriched air

• May allow divers to accomplish more for a given depth (between

40 metres/130 feet and 50 metres/165 feet).

• Time saved on complex mission may offset added deco time

when using more helium to reduce END.

• Don’t forget that narcosis is reduced but not eliminated, and may

still be a factor.

d. Reduced breathing effort at depth – trimix is easier to breathe than

air/enriched air

• Lighter helium may reduce breathing load if dive will be some-

what strenuous.

• Necessary to account for higher breathing rate in volume planning.

• Even with trimix the breathing gas is dense and a diver should

prevent getting winded or out of breath.

e. Because of reduced narcosis and breathing resistance, a trimix dive

often doesn’t feel as deep. You must constantly remind yourself thatyou’re deep, using gas quickly and racking up deco time.

2. The primary mission of any dive is for the entire team to return from

the dive unhurt.

a. Beware of too much mission focus. Accomplishing the mission is

desirable, but not necessary.

b. Be realistic in planning the mission – consider what you can really

accomplish amid the complexities of a trimix dive.

padi.com 3-79


XI. Practical Application Three

Practical Application Three has two primary purposes: 1) to continue

developing student fluency with desktop deco software and 2) to further

build dive planning skills for trimix dives by including detailed mission

planning.


be able to:

1. Working as a team and using desktop deco software, plan two

normoxic trimix dives, both with deep stops, one requiring two

decompression gases and the other with two or three decompres-

sion gases. The plans must include gas consumption, oxygen expo-

sure, decompression schedules, turn pressures and contingency

decompression schedules for each team member.

2. Working as a team, plan missions to be accomplished within these

two dives, accounting for time required, specific tasks, individual

team member duties and the effects on general dive planning.

A. Dive Planning

1. Group students into teams. Ideally, these should be the teams that

will dive together in Training Dives Three and Four. If necessary, staff

may participate as team members. Teams of three are ideal. For small

classes, a single team may be appropriate.

2. Assign student divers two dives to plan. Provide them with the

depth and time to plan based on the following.

a. These dives may be the actual dive plans and schedules teams use

for Training Dives Three and Four.

b. Both dives should be planned for normoxic (21 percent oxygen)

trimix.

c. The first dive is planned with two deco gases. This plan may

be the dive plan for Training Dive Three (30 metres/100 feet to

50 metres/165 feet depth). You may allow students to determine

what gases they will use or you may assign the gases to use based

on logistics. (See Training Dive Three for more details.)

d. The second dive may be

planned for two or three

deco gases. This plan may be

the dive plan for Training Dive

Four (40 metres/130 feet to

55 metres/185 feet depth). You

may allow students to deter-

mine what gases they will use

or you may assign the gases to

use based on logistics. (See

Training Dive Four for more

details.)

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e. Both dive plans must include

• deep stops. If the software doesn’t generate them, then students

enter them manually as waypoints.


rates.

• decompression schedule with runtime

• turn pressures



3. Assign teams two missions to plan for completion during Training

Dives Three and Four.

a. These missions may be entirely separate missions, or they may be

smaller parts of an overall larger goal requiring multiple dives, or

even multiple teams making multiple dives.

b. The mission is within your discretion, and may be based on the

environment and other local variables.

c. Choose missions that require some detailed planning and attention

to individual roles. Possibilities include but are not limited to:

• Assembling a PVC structure

• Mapping a wreck or portion of a wreck

• Identifying a sunken object

• Organism count

• Photo/video project

d. Remind student divers that completing the mission is not the pri-

ority; completing the dive safely as planned is the priority. You

may suggest they practice the mission on land or in shallow water,

as appropriate, as part of mission planning.

e. Teams should present their plans to you verbally or in writing

and include these elements:

• estimated time requirements

• individual roles

• predive preparation for the mission

• effect on general dive planning (gas selection, etc.)

f. The mission for Training Dive Four should allow student divers to

readily apply what they learned during Training Dive Three. The

Dive Four mission may therefore be an extension or repetition of the

Dive Three mission, or an entirely different mission that simply

allows students to apply what they’ve learned.

• Training Dive Four is optional for Tec Deep Diver certified stu-

dents, but they must complete the planning practical applica-

tion whether they will actually make the dive or not.

padi.com 3-81


XII. Training Dive Three




Diver’s Main Objective Is To Live procedure, and perform pre-

dive checks following the Being Wary Reduces All Failures pro-

cedures.

2. Working in a team, plan and execute a normoxic trimix acceler-

ated decompression dive using a table and/or multigas comput-

er and using air, enriched air, low helium/high oxygen trimix

and/or oxygen for decompression gases.

3. Working as a team, attempt to complete a dive mission

assigned by the instructor.

4. On a slate, correctly write down the decompression stops

and/or procedures to follow for an emergency missed decom-

pression stop, omitted decompression or delay in ascent pre-

sented by the instructor during decompression.

5. After completing all decompression and working as part of a

team, respond correctly to a simulated loss of decompression

gas emergency.





Training Dive Three is the first trimix dive. The

dive focus is on making the dive and attempting

the dive mission assigned in Practical Application

Three. You may assign skill practice and sponta-

neous drills, but student divers should have emer-

gency procedures mastered at this point, so it’s

best to keep these short and minimal and allow

students to learn through experience with the

actual dive. It is recommended that you assign any

drills not listed here as shallow water drills after

all decompression has been completed.

Note that divers should be displaying high levels

of dive skill, including equipment streamlining,

breathing control, antisilting, buoyancy control, stop depth control, etc.

With allowance for task loading and other unusual training demands, you

should expect the highest performance in these areas and remedy as nec-

essary. Student divers who do not meet this requirement may not con-

tinue into Training Dive Three. You may repeat Training Dives One

and/or Two as necessary until they demonstrate this skill level.

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TRAINING DIVE THREE

• Entry• Descent• Descent check• Dive mission• Ascent• Out of deco gas drill• Ascent procedures drill• Exit water (as appropriate

for environment)


gear as appropriate.• Log dive for instructor

signature


A. Training Dive Three Standards

1. Training Dive Three is conducted in open water as a trimix decom-

pression dive. The minimum depth is 30 metres/100 feet and the

maximum depth is 50 metres/165 feet.

2. Ratios – 2 students to 1 instructor, with 1 more student permitted





cal considerations.

3. Student divers and instructor must be equipped as described in the

Tec Deep Diver course, with accommodation for environmental

needs. This includes but is not limited to:


posts.





Diver course.

c. One or two stage/decompression cylinders

configured as described in the equipment

requirement section, and following the rig-

ging philosophies described in the Tec

Deep Diver course.

4. Gas requirements. Student divers and staff

may use air, enriched air, oxygen, low heli-

um/high oxygen trimix for decompression.

These may be any appropriate blends such as

air, EANx 32, 36, 50, 80, TMx32/10, TMx50/10,

etc. Back gas must be a normoxic trimix

(21 percent oxygen) with sufficient helium for an END equal to or

less than 40 metres/130 feet at the planned depth, or at least

20 percent helium, whichever is greater.

5. The decompression schedule should include deep stops, either gen-

erated by desktop deco software automatically or determined manu-

ally and inserted as waypoints.


1. Predive briefing







padi.com 3-83






c. Dive overview







– appropriate entry, don stage/deco

cylinders (at surface or before enter-

ing water)

– bubble check

– descent

– descent check

– dive mission

– follow trimix deco schedule with NO

TOX gas switches

– out of deco gas drill

– gas shutdown drill

• Time, depth and gas supply awareness –

assigned by instructor.





– Students must do this no matter what else is going on, short

of a real emergency.



dive plans.






they generate from a depth, trimix and two deco gases. They

should generate an entire plan with deco schedule, contingency

schedule, gas volume requirements, turn pressures and oxygen

exposure for each diver. You may have them do this by hand or

3-84 padi.com


use desktop deco software, or you may have them use the sched-

ule and plans from Practical Application Three as appropriate.

Allow ample time for proper planning, which may take an hour or

more. The final plans should include gas volume requirements for

all divers and may be presented on the TecRec Dive Planning

Slate or on a computer printout. It’s also recommended that you

have students laminate copies of their tables to carry on the dive.


All Failures.





close/open them.


C. Training Dive Three – suggested sequence



change.



and logistics).

c. Divers bubble check teammates.

It’s a good idea to have spare O-rings

at hand.

2. Descent

a. Descent check.

b. Stage cylinders at deco levels (if

appropriate to environment).

c. Continue descent to mission area.

3. Dive skills

a. Dive mission

• Completing the mission is notrequired because the primary dive

goal is the dive.

• The purpose is to give student

divers a chance to practice planning

and carrying out missions while

managing tec diving equipment and procedures.

b. Ascent and decompression with NO TOX gas switches.

• Team ascends following anchor/mooring line, bottom, lift bag line

or other appropriate reference available.


padi.com 3-85


• Emphasis should be on slow ascent rate and maintaining stop

depth. Students should not vary more than 1 metre/3 feet from

the stop depth during gas switches nor more than .6 metres/2 feet

after completing gas switch. Encourage teammates to help each

other maintain depth during switches and decompression.

c. Out of deco gas drill

• Conduct this drill after completing all

decompression, prior to surfacing.

• With a slate and/or signals, tell each

team it has five minutes of deco

remaining.

• Indicate a diver in each team who has

run out of the final (shallowest) deco

gas with the five minutes deco remain-

ing. That diver switches to the deeper

deco gas.

• The rest of the team completes its

deco with the “out of gas” diver’s deco clock stopped.

• After completing deco, one team member (let the team determine

who) switches to deeper deco gas and gives the remaining (shal-

lowest) deco gas to the “out of gas” diver.

• The team waits while the “out of gas” diver completes the remain-

ing five minutes of deco.

• Divers using multigas trimix computers should switch their com-

puters to the gases they’re using, even though they’ve actually

completed deco.

• Remind students that assisting this way only works when every-

one dives with the same gases.

d. Ascent procedures drill

• During or after decompression (but before surfacing), present

each diver with an omitted decompression, delay in ascent or

missed decompression stop problem on a slate. (e.g. “You just

accidentally ascended to the surface from 12 metres/40 feet and

returned to depth within one minute. What is your decompres-

sion schedule?”

• Student divers write the answer on a slate, but do not follow the

new schedule (so that the reserve isn’t compromised).

• Remind student divers to use their TecRec Emergency Procedures

Slate.

• If conducting this drill after completing all decompression, you

may have divers face away from the line and maintain stop depth

while determining the procedure and writing down the schedule.


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D. Post Dive









gases remaining. Have those with less refigure their SAC rates.

4. Debrief divers on the mission. Ask them what they learned and

what they will change on the next dive mission.



XIII. Training Dive Four




Diver’s Main Objective Is To Live procedure, and perform pre-

dive checks following the Being Wary Reduces All Failures pro-

cedures.

2. Working in a team, plan and execute a normoxic trimix acceler-

ated decompression dive using a table and/or multigas comput-

er and using air, enriched air, low helium/high oxygen trimix


3. Working as a team, attempt to complete a dive mission assigned

by the instructor.

4. Demonstrate time, depth and gas supply awareness by record-

ing depth, SPG pressure and time at intervals set before the


Note that Training Dive Four is optional for

students certified as DSAT Tec Deep Divers. It is

required for student divers entering the Tec

Trimix Diver course with a qualifying prerequi-

site certification from another training organi-

zation. You may require Tec Deep Diver certified

students to complete this dive in any case at

your discretion, such as to improve mastery,

allow additional learning time, or simply for

added experience with slightly more depth.

Training Dive Four is recommended for any stu-

dents who may benefit from extra practice. It

may be appropriate for any student whose per-

formance was acceptable in Training Dive Three,

padi.com 3-87

TRAINING DIVE FOUR

• Entry • Descent

• Descent check.

• Dive mission

• Ascent

• Exit water (as appropriate for environment)


gear as appropriate.• Log dive for instructor signature


but whose performance could rise markedly with added development.

Use this dive to emphasize streamlining, buoyancy control and body posi-

tion. Assign additional skills that require deploying and properly restow-

ing gear, with an emphasis on a

clean rig before and after the drill.

Training Dive Four follows the

Training Dive Three focus of making

the dive and attempting the dive

mission assigned in Practical

Application Three. The mission may

be an entirely new mission or the

Training Dive Three mission contin-

ued, with the goal of applying expe-

riences learned on Training Dive

Three to dive and mission of

Training Dive Four.

As with Training Dive Three, you

may assign skill practice and spon-

taneous drills, but students should

have emergency procedures mas-

tered at this point, so it’s best to keep these short and minimal and allow

students to learn through experience with the actual dive. It is recom-

mended that you assign any drills not listed here as shallow water drills

after all decompression has been completed.

A. Training Dive Four Standards

1. Training Dive Four is conducted in open water as a trimix decom-







accommodate student characteristics and environmental/logistical

considerations.





posts.





Diver course.

3-88 padi.com


c. One or two stage/decompression cylinders configured as

described in the equipment requirement section, and following

the rigging philosophies described in the Tec Deep Diver course.

4. Gas requirements. Students and staff

may use air, enriched air, oxygen, low

helium/high oxygen trimix for decom-

pression. These may be any appropriate

blends such as air, EANx 32, 36, 50, 80,

TMx32/10, TMx50/10, etc. Back gas

should be a normoxic trimix (21 percent oxygen) with sufficient heli-

um for an END equal to or less than 40 metres/130 feet at the

planned depth, or at least 20 percent helium, whichever is greater.





1. Predive briefing











c. Dive overview


• It’s recommended that you have students

write down the dive overview and notes on a

slate for reference during the dive, and to

have them do this for each dive.

• Skill overview – describe each skill, the per-

formance requirement and how you’ll con-

duct it, including signals, etc.

– appropriate entry, don stage/deco cylin-

ders (at surface or before entering water)

– bubble check

– descent

– descent check

– dive mission — apply lessons learned in Training Dive Three


padi.com 3-89

It is recommended that you

have student divers use

three cylinders for this dive.


– loss of decompression gas drill (after completing decompres-

sion) – you may repeat this drill with a different diver out of

deco gas






– Student divers must do this no matter what else is going on,

short of a real emergency.



dive plans.






they generate from a depth, trimix and deco gases. They should

generate an entire plan with deco schedule, contingency sched-

ule, gas volume requirements, turn pressures and oxygen expo-

sure for each diver. You may have them do this by hand or use

desktop deco software, or you may have them use the schedule

and plans from Practical Application Three as appropriate. Allow

ample time for proper planning, which may take an hour or more.

The final plans should include gas volume requirements for all

divers and may be presented on the TecRec Dive Planning Slate or

on a computer printout. It’s also recommended that you have stu-

dents laminate copies of their tables to carry on the dive.


All Failures.



– Touch drill while geared up and seated, student divers reach

back and touch (grasp) regulator and isolator valves as if to

close/open them.


C. Training Dive Four – suggested sequence



change.


3-90 padi.com



and logistics).


O-rings at hand.

2. Descent

a. Descent check.

b. Stage cylinders at deco levels (if appropriate to environment).


3. Dive skills

a. Dive mission

• Completing the mission is not required because the primary dive

goal is the dive.

• The purpose is to give student divers a chance to practice plan-

ning and carrying out missions while managing tec diving equip-

ment and procedures.

• The mission for this dive should be something that readily allows

students to apply what they learned through experience in

Training Dive Three.

b. Ascent and decompression with NO TOX gas switches.

• Team ascends following anchor/mooring line, bottom, lift bag line

or other appropriate reference available.


padi.com 3-91


• Emphasis should be on slow ascent rate and maintaining stop

depth. Students should not vary more than 1 metre/3 feet from

the stop depth during gas switches nor more than .6 metres/

2 feet after completing gas switch. Encourage teammates to help

each other maintain depth during switches and decompression.

c. Out of deco gas drill

• Conduct this drill after completing all decompression, prior to

surfacing.

• With a slate and/or signals, tell each team it has five minutes of

deco remaining.

• Indicate a diver in each team who has run out of the final (shal-

lowest) deco gas with the five minutes deco remaining. That diver

switches to the deeper deco gas. This should be a different diver

from the one chosen in Training Dive Three.

• The rest of the team completes its deco with the “out of gas”

diver’s deco clock stopped.

• After completing deco, one team member (let the team determine

who) switches to deeper deco gas and gives the remaining (shal-

lowest) deco gas to the “out of gas” diver.

• The team waits while the “out of gas” diver com-

pletes the remaining five minutes of deco.

• Divers using multigas trimix computers should

switch their computers to the gases they’re using,

even though they’ve actually completed deco.

• Remind students that assisting this way only works

when everyone dives with the same gases.


D. Post Dive

1. Performance review. After giving divers some time to

rest, get a drink, etc., but while memories remain fresh,

have teams identify what happened, what they learned,

what worked and what didn’t, etc. Comment and fill in

missing information as necessary, but have students

critique themselves constructively while you guide the

process.



3. Debrief divers on the mission. Ask them what they learned and what

they will change on the next dive mission.





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XIV. Knowledge Development Presentation Four

A. Thinking Like a Trimix Diver IV



1. What are the limits of trimix diving?

2. What are the limits of your training in the Tec Trimix Diver

course?

3. How do you extend your limits as a Tec Trimix Diver?

4. What are your responsibilities as a Tec Trimix Diver with

respect to the state of the art in trimix diving in particular, and

technical diving in general?

5. What is the most important personal quality with respect to

extending your limits?

1. The Limits of Trimix Diving

a. To review what you learned in Knowledge Development

Presentation One:

• Typical range for new, beginning trimix divers is to 75 metres/

245 feet, or the maximum depth experienced during training.

• Experienced trimix divers venture as deep as 90 metres/300 feet.

• Dives between 90 metres/300 feet and 120 metres/400 feet are not

unusual for highly experienced exploratory divers – beyond accept-

ed range for beginning trimix divers.

• As you know, the maximum depth for this course is 75 metres/

245 feet.

padi.com 3-93

THE LIMITS OF TRIMIX DIVING

New, beginning trimix divers is to 75 metres/245 feet, or the maximum depth experienced during training.

Experienced trimix divers venture as deep as 90 metres/300 feet.

Dives between 90 metres/300 feet and 120 metres/ 400 feet arenot unusual for highly experienced exploratory divers – beyondaccepted range for beginning trimix divers.


3-94 padi.com

b. By its nature, tec diving pushes limits. The limits of trimix diving in

general, trimix diving with open circuit scuba and trimix diving with

closed circuit scuba are still being explored.

2. Your Limits

a. Your immediate limit for open water trimix diving after completing

this course is 75 metres/245 feet or the maximum depth you reached

in training (whichever is less) in conditions comparable to those in

which you trained.

• these conditions include visibility, temperature, fresh or salt

water, etc.

• also consider water motion – waves, surge and current

• consider anything that affects equipment configuration and/or

procedures as new conditions

b. To extend your limits and the conditions in which you trimix dive,

you need to give yourself time and experience.

• Make your first several dives after certification well within the

limits of your training.

• As necessary and according to your risk tolerance and interest,

extend your limits gradually by making dives progressively deeper

or in more challenging conditions in small steps.

• Avoid pushing both environmental and depth limits together.

Work deeper in environments and conditions that you know well

and handle easily. When challenged by a new environment, master

it on shallow dives first.

• Team up with more experienced divers.

c. Your limits will expand over time if that’s your interest.

3. Your Responsibilities as a Tec Trimix Diver

a. It is your responsibility to accept the risks of trimix diving, tec div-

ing and the mounting risks that accompany expanding your limits.

b. It is your responsibility to stay informed with respect to the state of

the art in tec diving in general, and trimix diving in particular.

• Technology and procedures continue to change based on experi-

ences and accidents.

4. The most important personal quality you can have with respect to

extending your limits and staying current for tec diving is patience.

a. Don’t be in a hurry to push limits; gain experience slowly and care-

fully.

b. It takes time to stay current; invest the time to do so and/or refresh

and practice as necessary.

c. Don’t let anyone talk you into a dive you’re not ready for. Saying

“no” is not only the safe, smart thing to do, but will earn you respect

and a reputation as a diver who knows and stays within personal

limits.


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B. Equipment III – Crush Depth

Learning Objectives: By the end of this section, you should be

able to answer these questions:

1. What is “crush depth” for a piece of equipment?

2. Why is crush depth an issue for trimix diving?

3. How do you determine a piece of equipment’s depth rating?

4. What is the safest course with respect to avoiding crush

depth?

5. What risks do you face by exceeding equipment’s depth

rating?

6. What other depth-related equipment issues might you

encounter as a trimix diver?

7. What should you look for with respect to equipment rated to

deep depths?

1. As a trimix diver, you have to concern yourself with crush depth,which is the depth at which equipment can

fail due to water pressure.

a. primarily a concern for sealed, air filled

equipment like dive lights, camera housings,

strobes, watches, SPGs, electronic communi-

cations equipment

b. may also be a concern with respect to any-

thing made of a compressible material like

styrofoam or neoprene

2. Crush depth is an issue for trimix diving

because much dive equipment was designed for

recreational diving to 40 metres/130 feet.

a. Tec diving to 50 metres/165 feet is generally

not an issue because this is within the design

specs for most gear.

b. As you go deeper, this becomes more of a

concern, especially below 60 metres/200 feet.

3. You normally determine the depth rating for equipment by consult-

ing the manufacturer’s literature, or contacting the manufacturer.

a. In some cases, it may be wise to test equipment by taking it to the

desired depth, either to confirm manufacturer specs or because

they’re not available.

b. However, pressure stress can be cumulative – equipment may fail

after several deep dives.

c. The lowest failure risk is to use equipment specifically designed

for the desired depth.

4. Diving to or beyond a piece of equipment’s rated depth (to crush

depth) poses several possible risks.


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a. Catastrophic failure, in which the item implodes forcefully (hence the

name “crush depth”)

• relatively rare, but possible

• some risk of injury with a large item

• sudden negative buoyancy can create a hazard, such as if clipped

to a DPV that implodes

b. Seal failure, cracking – water pressure causes seal to fail totally, water

seeps in past the seals, or pressure cracks housing allowing water to

seep in likely result with camera housings, strobes, DPVs and other

devices with multiple intricate controls through the housing

• cracking more likely with lights and air filled gauges

• unit floods, with internal damage (depends on the device) and

buoyancy loss

c. Non catastrophic crush – pressure distorts the equipment affecting it

internally

• SPG is a common example – gauge face bends in and presses on

mechanism so it can’t move

• housings/electronics – water pressure depresses and/or freezes

controls

• electronics – water pressure squeezes circuit boards together caus-

ing short circuits and failure

• lights – may crush batteries internally

• equipment held by snug fit with neoprene or styrofoam may come

loose due to material compression

5. Other depth-related effects

a. Most electronic gauges/computers have depth limits – commonly

100 metres/330 feet for air/EANx computers (or less for some models,

and deeper for trimix models)

• consult manufacturer literature

• failure to stay within your gauge’s range can leave you without

depth/time information if instrument enters error or out-of-range

mode

• some air/EANx computers function as computers to 100 metres/330

feet, but can be set for gauge-only function to much deeper depths

b. BCD/dry suit inflation

• As you go deeper, increased gas density slows speed at which your

BCD and/or dry suit inflate.

• Noticeable as shallow as 30 metres/100 feet, but becomes very

noticeable as you approach 60 metres/200 feet.

• Make a habit of inflating often to maintain buoyancy. Avoid long,

drawn out bursts that can cause regulator freeze, especially in cold

water.


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• Some divers prefer high volume inflation system to help counter

this.

c. Wet suits

• Will insulate far less effectively at extreme depth due to neoprene

compression.

• Some types of neoprene crush permanently when taken to trimix

depths, resulting in permanent insulation and buoyancy loss.

d. Regulators

• Some regulators, especially less costly, lower performance mod-

els, may have noticable delivery problems at trimix depths.

• This is why high per-

formance regulators

are the best choice

for trimix (reliable,

lower end regulators

may be fine for shal-

low use on decom-

pression cylinders).

e. Decompression model

• Some anecdotal

reports suggest that

current deco model-

ing methodologies

become less reliable

below 100 metres/330 feet.

• Anecdotal reports suggest higher DCS incidence rate and the

need for more conservatism at these depths.

• This is largely theoretical and a question of what’s not known

more than what is known.

6. Choosing depth rated equipment

a. Check the manufacturer rating and select equipment that’s rated

deeper than your intended use depth (if possible).

b. Liquid filled gauges resist pressure far better than air-filled (but they

cost more).

c. Multigas trimix computers are generally rated much deeper than

other computers. Be sure your backup depth and time instruments

are rated to the same depths, though.

d. Large items like light canisters and DPVs tolerate pressure far better

with internal bulkheads.

e. Pay close attention to camera housing depth ratings. Relatively few

have ratings deeper than 75 metres/245 feet, they tend to leak easily

if taken too deep, and the consequences can be very expensive.


XV. Practical Application Four

Practical Application Four has the primary purpose of turning dive plan-

ning over to students (in teams) almost entirely, with you/staff available to

provide assistance.


be able to:


trimix dives, both with deep stops. The plans must include gas con-

sumption, oxygen exposure, decompression schedules, turn pres-

sures and contingency decompression schedules for each team

member.

2. Working as a team, plan a team-chosen mission studying pressure

effects on an object, to be accomplished within the second of the

two dives, accounting for time required, specific tasks, individual

team member duties and the effects on general dive planning. The

mission must be integrated into the effect, time and logistics of the

over all dive plan.

A. Dive Planning

1. Divide students into teams. Ideally, these should be the teams that will

dive together in Training Dives Five and Six, so teams of two, or three

with a certified assistant, are recommended.

2. Assign students two dives to plan. They are to entirely plan the dives,

within the following limits and restrictions that you provide:


for Training Dives Five and Six.

b. The depth range for the dives is 45 metres/150 feet to 67 metres/

220 feet. You may specify a narrow range within this range if neces-

sary for logistical/environmental purposes. You may specify time

ranges for logistical purposes as well.

c. The bottom trimix must have 16 percent or higher oxygen. You may

specify a range, but there should be choices.

d. The dives may have two to four deco gases. You may specify a range

of gases, but there should be choices. You may also limit the deco

gases to two or three if necessary for logistical/environmental rea-

sons and these will be the plans for the actual dives.


• deep stops. If the software doesn’t generate them, then student

divers enter them manually as waypoints.


rates.

• bottom time and decompression schedule with runtime

• turn pressures

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3. Assign teams missions to plan for completion during Training Dives

Five and Six.

a. Each team develops and plans its own mission (with your approval)

for Dive Five. Allow anything that the team wants to accomplish pro-

vided it doesn’t violate the dive limits or create an undue hazard. The

purpose is to allow teams to learn to gauge what they want to accom-

plish and what they can accomplish. Note that teams must also allow

time for the required dive skills (See Dive Five details) within the

planned bottom time.

b. The way to accomplish the mission for Dive Six is to be created

and chosen by each team, but must involve measurably document-

ing pressure-related effects on one or more object. The team

should plan to provide specific measurements, photos, etc. of the

object(s) before, during and after the dive. You may provide sugges-

tions based on the environment and local variables. The purpose is

to allow teams to adapt to a mission they didn’t choose, but must

create the methodology. Note: The mission must document the pres-

sure in a way that’s visible to someone who didn’t make the dive.

c. Remind student divers that completing the mission is not the prior-

ity; completing the dive safely as planned is the priority.

• Emphasis should be that the mission is important (or why make

the dive), but that safety is the priority.

• Students should remember that the point of practicing missions is

so that their trimix dives will have a useful purpose.

d. Teams should present their plans to you and include these

elements:




• effect on general dive planning (gas

selection, etc.)

• mission (goal and method for Dive

Five, and how the pressure effect will

be measured and documented for

Dive Six).

e. The plan should show how the mission

will be accomplished within the dive

plan for Training Dive Eight. If you are

having students plan example dives well

ahead of the actual training dives, have teams replan mission integra-

tion when they plan the actual Training Dive Eight.

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f. Provide comments, suggestions and/or changes to both dive plans

as appropriate.

B. Tec Trimix Diver Exam

Administer the Tec Trimix Diver Exam. After completing the exam, review

questions missed with students individually. Eighty percent is the mini-

mum score without retaking the exam; however, students must demon-

strate mastery on all items missed.

XVI. Training Dive Five

To successfully complete this training dive, the student will

be able to:





procedures.

2. Working in a team, plan and execute a trimix accelerated

decompression dive using a table and/or multigas computer

and using air, enriched air, low helium/high oxygen trimix


3. On the bottom, respond correctly to a simulated regulator

freeflow or manifold failure.

4. On the bottom, respond correctly to a simulated runaway infla-

tor (primary BCD or backup inflation system).

5. Working as a team, reasonably attempt to

accomplish a mission they’ve chosen

together.

6. As a team, deploy a lift bag from the

bottom.

7. As a team, send a second lift bag up the

line of the previously deployed lift bag.

8. While decompressing, respond to an

ascent emergency scenario presented by

the instructor by writing the correction

action, including any modified stop times,

on a slate.





Training Dive Five allows students to practice pre-

viously mastered emergency skills assigned while at depth.

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TRAINING DIVE FIVE

• Entry• Descent• Descent check• Dive mission• Failed bag drill• Ascent• Emergency scenarios during ascent• Exit water (as appropriate

for environment)





A. Training Dive Five Standards

1. Training Dive Five is conducted in open water as a trimix decom-








cal considerations.





posts.





Diver course.

c. Two or three stage/decompression cylinders configured as



4. Gas requirements. Students and staff may use air, enriched air, oxy-

gen, low helium/high oxygen trimix for decompression. These may

be any appropriate blends such as air, EANx 32, 36, 50, 80, TMx32/10,

TMx50/10, etc. Back gas should be a trimix with 21 to 16 percent

oxygen and with sufficient helium for an END equal to or less than

40 metres/130 feet at the planned depth. It is recommended that you

have students simulate starting the dive using one of the deco gases

as a travel gas, figuring the gas consumption into their dive plans.

5. The decompression schedule should include deep stops, either

generated by desktop deco software automatically or determined

manually and inserted as waypoints.


1. Predive briefing









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c. Dive overview









– students use travel or appropriate deco gas at surface

– bubble check

– descent

– NO TOX switch to back gas at planned depth; descent check

– freeflow regulator/failed manifold drill

– runaway inflator drill

– mission

– team deploys lift bag

– team deploys second lift bag along first bag’s line


– emergency decompression procedures










dive plans.



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[Note to instructor: Bottom time may be short on this

dive, and there are several required skills. You may

want to schedule the skills before candidates attempt

the mission, since finishing the mission is secondary.]









desktop deco software. Practical Application Four may be this

planning session. Allow ample time for proper planning, which

may take an hour or more. The final plans should include gas vol-

ume requirements for all divers and may be presented on the

TecRec Dive Planning Slate or on a computer printout. It’s also

recommended that you have students laminate copies of their

tables to carry on the dive.







close/open them.


C. Training Dive Five – suggested sequence



change.



and logistics).


O-rings at hand.

d. Divers use appropriate deco gas as simulated travel gas at surface.

Teammates confirm correct gas use.

2. Descent

a. Descend and stop at planned depth for switch to back gas.

b. Student divers NO TOX switch to back gas.

c. Descent check.

d. Stage cylinders at deco levels (if appropriate to environment).

e. Continue descent to mission area.

3. Dive skills

a. Freeflow regulator or manifold failure

• Signal to students that either back gas second stage is free flow-

ing or the manifold has failed.

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• Do not simulate the freeflow by holding in the purge button

because this is an actual decompression dive and doing so wastes

reserve gas. Use a slate or signal.

• Diver shuts appropriate valve and switches second stage if appro-

priate.

• Confirm valve reopened and breathing from primary second stage

after finishing exercise.

b. Runaway inflator drill

• Signal that the diver’s primary or secondary inflator is leaking.

• Diver disconnects leaking inflator and switches to secondary

(backup) buoyancy system.

• Confirm inflator hose reconnected and operational after conclud-

ing exercise.

c. Mission – as time allows.

• Allow ample time for lift bag deployment within planned bottom

time.

d. Deploy lift bag.

e. Failed bag drill – send second bag up first bag’s line.

f. Ascent and decompression with NO TOX gas switches

• Team may ascend and drift under lift bag, ascend another line

(anchor or mooring) towing bag, or having bag retrieved by staff

at the surface, as appropriate.

• During decompression, you present emergencies based on

those listed on the TecRec Emergency Procedures slate.

– Example: Write “You’ve just returned to this stop after acciden-

tally ascending to the surface and returning after six minutes

with no DCS symptoms. What would you do?”

• Student responds by writing out the correct action, including

stop times on a slate.

– Emphasize that students will not actually follow the emer-

gency schedule. This is because doing so would consume the

students’ reserves, which should be conserved in case a real

emergency should arise.

– Student divers may consult the TecRec Emergency Procedures

Slate.

• Present these problems at depths with more than one or two min-

utes stop so students can answer without accidentally compro-

mising their deco schedule.


D. Post Dive




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4. Debrief divers on their skills and emergencies.



XVII. Training Dive Six




Diver’s Main Objective Is To Live procedure, and perform predive

checks following the Being Wary Reduces

All Failures procedures.

2. Working in a team, plan and execute a

trimix accelerated decompression dive

using a table and/or multigas computer

and using air, enriched air, low

helium/high oxygen trimix and/or oxygen

for decompression gases.

3. As a team within the dive plan limits,

execute a mission to study and document

in a measurable method the effects of

pressure on one or more objects.

4. While decompressing, respond to an

ascent emergency scenario presented by

the instructor by writing the correction

action, including any modified stop times,

on a slate.


awareness by recording depth, SPG pressure and time at inter-

vals set before the dive by the instructor.

Training Dive Six allows students to put into practice a dive plan integrat-

ed with a mission that they’ve developed as a team, with you and/or

instructional staff providing primarily only guidance.

A. Training Dive Six Standards

1. Training Dive Six is conducted in open water as a trimix decompres-

sion dive. The minimum depth is 45 metres/150 feet and the maxi-

mum depth is 67 metres/220 feet.

2. Ratios – 2 students to 1 instructor, with 1 more student permitted with

a certified assistant to a maximum of 3. (See Section Two for specific

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TRAINING DIVE SIX

• Entry

• Descent

• Descent check

• Pressure effects mission

• Free time as available

• Ascent

• Emergency scenarios during ascent






requirements necessary to qualify as a certified assistant in this course.)

These are maximums – reduce ratios as necessary to accommodate stu-

dent characteristics and environmental/logistical considerations.





posts.





Diver course.

c. Two or three stage/decompression cylinders configured as






TMx50/10, etc. Back gas should be a trimix with at least 16 percent

oxygen and with sufficient helium for an END equal to or less than

40 metres/130 feet at the planned depth.





1. Predive briefing











c. Dive overview


• It’s recommended that you have student divers write down the

dive overview and notes on a slate for reference during the dive,




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– bubble check

– descent

– descent check

– pressure effects mission

– free time to explore (time allowing)

– emergency decompression procedures










dive plans.










desktop deco software. Practical Application Four may be this













close/open them.


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C. Training Dive Six – suggested sequence



change.



and logistics).

c. Divers bubble check teammates. It’s a

good idea to have spare O-rings at hand.

2. Descent

a. Descent check.

b. Stage cylinders at deco levels (if appro-

priate to environment).


3. Dive skills

a. Pressure effects mission.

b. Free time to explore – as time allows.

c. Ascent and decompression with NO TOX gas switches.

• Team may ascend and drift under a lift bag, or other ascent refer-

ence and technique as appropriate to the environment.

• During decompression, you present emergencies based on

those listed on the TecRec Emergency Procedures slate.

– EXAMPLE: Write “You’ve just returned to this stop after acciden-

tally ascending to the surface and returning after six minutes

with no DCS symptoms. What would you do?”

– Present a different problem from the one you gave each team in

Training Dive Five.

• Student responds by writing out the correct action, including

stop times on a slate.

– Emphasize that student divers will not actually follow the

emergency schedule. This is because doing so would consume

the students’ reserve, which should be conserved in case a real

emergency should arise.

– Students may consult the TecRec Emergency Procedures Slate.

• Present these problems at depths with more than one or two min-

utes stop so students can answer without accidentally compro-

mising their deco schedule.


D. Post Dive

1. Performance review.



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4. Debrief divers on the mission and skills practiced.



XVIII. Practical Application Five

Practical Application Five has the primary purpose of turning dive plan-

ning over to students (in teams) almost entirely, with you/staff available

to provide assistance.


be able to:


trimix dives, both with deep stops. The plans must include gas

consumption, oxygen exposure, decompression schedules, turn

pressures and contingency decompression schedules for each

team member.

2. Working as a team, plan a team-chosen mission for each dive.

A. Dive Planning

1. Divide students into teams. Ideally, these should be the teams that will

dive together in Training Dives Seven and Eight.

2. Assign students two dives to plan. They are to entirely plan the

dives, within the following limits and restrictions that you provide:


for Training Dives Seven and Eight.

b. The depth range for the dives is 55 metres/180 feet to 75 metres/

245 feet. You may specify a narrow range within this range if neces-

sary for logistical/environmental purposes. You may specify time

ranges for logistical purposes as well.

c. The bottom trimix may be any suitable blend with an END of

40 metres/130 feet or shallower. You may specify a range, but there

should be choices.

d. The dives may have two to four deco gases. You may specify a range

of gases, but there should be choices. You may have them generate

plans with more deco gases and/or different deco gases than they’ll

actually use on Training Dives Seven and/or Eight, then regenerate

the plans with the actual gases they’ll use for comparison.


• deep stops. If the software doesn’t generate them, then students

enter them manually as waypoints.


rates.

• bottom time and decompression schedule with runtime

• turn pressures

padi.com 3-109




3. Assign teams to plan missions to complete during Training Dives

Seven and Eight.

a. These dives are the final and deepest dives of the course. The

emphasis should be on executing well planned dives according to

the plan, so encourage reasonable missions. The missions may be

subtasks for an overall mission completed over both dives and/or

by multiple teams.

• Be ready to suggest a mission or missions if teams cannot (may

be an issue due to relative unfamiliarity with the dive site).

b. Remind student divers that completing the mission is not the pri-

ority; completing the dive safely as planned is the priority.

c. Team should present their plans to you verbally or in writing and

include these elements:




• effect on general dive planning (gas selection, etc.)

d. Provide comments, suggestions and/or changes to both dive plans

as appropriate.

XIX. Training Dive Seven




Diver’s Main Objective Is To Live proce-

dure, and perform predive checks follow-

ing the Being Wary Reduces All Failures

procedures.




and using air, enriched air, low helium/

high oxygen trimix and/or oxygen for

decompression gases.

3. As a team and within the dive plan limits,

execute a mission chosen by the team.

Training Dive Seven allows students to put into

practice basic dive plans and missions that they

develop with your/staff guidance only. Given this

and the final dives are the deepest dives in the

course, the emphasis is on executing the dive as planned.

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TRAINING DIVE SEVEN

• Entry

• Descent

• Descent check

• Mission

• Ascent






A. Training Dive Seven Standards

1. Training Dive Seven is conducted in open water as a trimix decom-







accommodate student characteristics and environmental/logistical

considerations.




a. Manifolded double cylinders with dual,

independent regulator posts.

b. Technical diving BCD, redundant buoy-

ancy device (double bladder BCD, or dry

suit if appropriate for weight of gear

worn) and harness as described in the

equipment requirement section, and fol-

lowing the rigging philosophies described

in the Tec Deep Diver course.

c. Stage/decompression cylinders as

required configured as described in the

equipment requirement section, and following the rigging

philosophies described in the Tec Deep Diver course.




TMx50/10, etc. Back gas should be a trimix with sufficient helium for

an END equal to or less than 40 metres/130 feet at the planned

depth, and 16 to 21 percent oxygen.





1. Predive briefing

a. Group in teams, student divers set up their rigs, analyze gases, but

do not yet don exposure suits.







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c. Dive overview









– bubble check

– descent

– descent check

– mission



dive plans.










desktop deco software. Practical Application Five may be this





recommended that you have student divers laminate copies of

their tables to carry on the dive.


All Failures.





close/open them.


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C. Training Dive Seven – suggested sequence



change.

b. Divers don stage/deco cylinders at surface with minimal assistance, or

prior to entering water (as appropriate for environment and logistics).

c. Divers bubble check teammates. It’s a good idea to have spare O-rings

at hand.

2. Descent

a. Descent check.



3. Dive skills

a. Mission

b. Ascent and decompression with NO TOX gas switches




D. Post Dive







XX. Training Dive Eight


1. Working within the student’s assigned

team, rig gear, including stage/deco

cylinders, and plan the dive following

the A Good Diver’s Main Objective Is To

Live procedure, and perform predive

checks following the Being Wary

Reduces All Failures procedures.




and using air, enriched air, low heli-

um/high oxygen trimix and/or

oxygen for decompression gases.

3. As a team and within the dive plan

limits, execute a mission chosen by the

team.

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TRAINING DIVE EIGHT

• Entry

• Descent

• Descent check

• Mission

• Ascent






Training Dive Eight allows students to put into practice basic dive plans

and missions that they develop with your/staff guidance only. As the final

dives are the deepest dives in the course, the emphasis is on executing

the dive as planned.

A. Training Dive Eight Standards

1. Training Dive Eight is conducted in open water as a trimix decom-








cal considerations.





posts.





Diver course.

c. Stage/decompression cylinders as required configured as






TMx50/10, etc. Back gas should be a trimix with sufficient helium for

an END equal to or less than 40 metres/130 feet at the planned

depth, and 21 to 16 percent oxygen.





1. Predive briefing







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c. Dive overview









– bubble check

– descent

– descent check

– mission

• Review hand signals, emer-

gency protocols, descent and

ascent procedures, final

details. Assign each team to

complete individual dive

plans.

• Remind divers they are car-

rying gases that they cannot

safely breathe at the bottom

depth.








desktop deco software. Practical Application Five may be this









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– Student divers use TecRec Equipment Checklist to confirm

each other’s equipment setup.



close/open them.


C. Training Dive Eight – suggested sequence



change.



and logistics).


O-rings at hand.

2. Descent

a. Descent check.



3. Dive skills

a. Mission

b. Ascent and decompression with NO TOX gas switches




D. Post Dive







E. Graduation Event – hold a social event to celebrate student diver suc-

cess, recognize their accomplishments and complete the final paperwork

for certification as Tec Trimix Divers. Suggested: slide show or video from

the course (shot by a staff member), plus slides/videos of upcoming

trips/dives suited to Tec Trimix Divers.

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Tri mix instructor guide

Sports

Transcript of Tri mix instructor guide