Tec40

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Instructor Guide Section four: Tec40

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four: Tec 40 Standards and Course Content

The Tec 40 subcourse of the DSAT Tec Diver course is a limited, entry-level technical

diving program that bridges the gap between recreational diving and full technical deep decom-

pression diving. Certified Tec 40 divers are qualified to make limited decompression dives

using equipment that is marginally more extensive than that used in mainstream recreational

diving.

Program SequenceThe Tec 40 course consists of three knowledge development sections, three practical

applications sessions and four training dives. You will find these in the Knowledge

Development, Practical Application and Training Dive subsections, each with content/presenta-

tion outlines and related standards.

The fully integrated instructional sequence for the Tec 40 course is:

Tec 40 Knowledge Development One

Tec 40 Practical Application One

Tec 40 Training Dive One

Tec 40 Knowledge Development Two

Tec 40 Practical Application Two

Tec 40 Training Dive Two

Tec 40 Knowledge Development Three

Tec 40 Practical Application Three

Tec 40 Exam

Tec 40 Training Dive Three

Tec 40 Training Dive Four

The Tec 40 course provides flexibility in scheduling knowledge development, practical

applications and training dives. You may rearrange the sequence and combine knowledge

development and practical applications sessions, provided that you maintain the required

instructional sequencing. The requirements are:

• Any knowledge development sections, practical applications or training

dives that precede a training dive in the integrated sequence must be suc-

cessfully completed before that training dive.

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Section four: Tec40 Instructor Guide

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• Any knowledge development sections or practical applications that

precede a practical application in the integrated sequence must be suc-

cessfully completed before that practical application.

• Any knowledge development section that precedes another knowledge

development section must be successfully completed before that

knowledge development section.

For example, the following sequences would be acceptable:









Tec 40 Exam










Tec 40 Exam




Special sequence exception for the Tec 40 course: To allow student divers to

start the Tec Diver course immediately (Dive Today), Tec 40 Training Dive One may

precede Tec 40 Knowledge Development One and Tec 40 Practical Application One.

Follow the Dive Today Considerations that accompany Tec 40 Training Dive One.

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Training Dive one Environment: Confined water or limited open water with ready access to water shallow enough in which to stand Depths: Minimum: 2.5 metres/8 feet Maximum 10 metres/30 feet Decompression: No stop only Gases: Air, EANx up to EANx50 Ratios: 6:1, 8:1 with one or more certified assistants

Training Dive Two Environment: Open water Depths: Minimum: 10 metres/30 feet Maximum: 18 metres/60 feet Decompression: No stop only Gases: Air or EANx up to EANx50. Ratios: 6:1, 8:1 with one or more certified assistants

Training Dive Three Environment: Open Water Depths: Minimum: 15 metres/50 feet Maximum: 27 metres/90 feet Decompression: No stop only Gases: Air, EANx up to EANx50 Ratios: 4:1, 6:1 with one or more certified assistants

Training Dive four Environment: Open Water Depths: Minimum: 26 metres/85 feet Maximum: 40 metres/130 feet Decompression: Up to 10 minutes total decompression time based on breathing bottom gas throughout the dive (no accelerated decompression) Gases: Air, EANx up to EANx50 Ratios: 3:1, 4:1 with one or more certified assistants

Tec 40 Key Standards Participant prerequisites: Certified as a PADI Advanced Open Water Diver or a qualifying certification from another training organization, PADI Enriched Air Diver or a qualifying certification from another training organization, PADI Deep Diver or proof of 10 dives to 30 metres/100 feet, 18 years old, 30 logged dives (10 with EANx, 7 deeper than 30 metres/100 feet).Instructor qualification: Teaching status, insured (where required) Tec InstructorAssistant qualification: renewed PADI Divemaster or higher certified as a Tec 40 or higher level TecRec diver.

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Tec 40 Knowledge DevelopmentThe following knowledge development outlines provide the course content in

presentation form. If the Tec Deep Diver Manual is not available in a language the

student understands, you may use the outline to present all course content.

Otherwise, it is recommended that you cover knowledge development through stu-

dent independent study with the manual and handouts, with presentations that

review/remediate what they studied.

The content outlines note manual supported content and other delivery

content. The manual supported content includes a list of reading, exercise and

Knowledge Review assignments (repeated in list form in the Appendix for your con-

venience) based upon the Tec Deep Diver Manual. The other delivery content covers

material that is not in the Tec Deep Diver Manual. You may simply deliver this

material in verbal presentations using the Tec Diver Lesson Guides on PowerPointTM,

or (recommended) you can copy those outline sections for students to study inde-

pendently along with their assignments in the manual. These sections are in the

Appendix ready for copy and handout. Presentations that involve staff introductions,

paperwork, logistics, scheduling etc., do not have independent study materials.

Tec 40 students do not use the Knowledge Reviews in the Tec Deep Diver

Manual. Instead, copy the blank Tec 40 Knowledge Reviews in the Appendix for

their use. You will also find the answer keys there. Students have not completed a Knowledge Development session until they have completed the corresponding Knowledge Review correctly, accurately and completely.

The final step in completing Tec 40 Knowledge Development is the Tec 40

Exam. Tec 40 students complete the exam after successfully completing Knowledge Development Three. To be successful, the student diver must score 80% or higher and review each question missed with the instructor until mas-tery on all questions is achieved. Students who score less than 80% must repeat the exam (version B) after ample time to remediate. It is recommended that you

administer the exam after Tec 40 Practical Application Three.

All material in the Knowledge Development content outline is required and must be covered, studied and otherwise remediated until the student dem-onstrates mastery.

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Tec 40 Knowledge Development one[The voice in these presentations addresses students. Notes to the instructor appear in

brackets.]

I. Introductory SessionLearning Objectives

By the end of this section, you should be able to answer these questions:

1. What are the goals of the Tec 40 course?

2. What are your obligations and responsibilities in taking this course?

3. What are consequences of failing to meet these obligations and responsibilities?

A. Introductions [Encourage a relaxed atmosphere that promotes teamwork.]

1. [Introduce yourself, staff and anyone else involved in the course. Provide

a little bit of background and personal information about everyone so stu-

dents become acquainted.]

2. [Have students introduce themselves and tell something about themselves,

diving interests, etc.]

3. [Collect and review Tec 40 Knowledge Review One.]

a. [Review answers to assess mastery so you can tailor your presenta-

tions accordingly.]

B. Course Goals

1. The goals of the Tec 40 course are

a. To qualify you to make limited decompression dives at a level that

bridges recreational diving and technical diving.

b. To train you in the knowledge, procedures and motorskills required

for decompression diving within the limitations of the Tec 40 certi-

fication.

c. To assure you understand and acknowledge the hazards and risks

associated with this level of tec diving, and tec diving in general.

d. To train you to prepare for and respond to reasonably foreseeable

emergencies that may occur within Tec 40 limits.

e. To lay the foundation for continuing your training as a full techni-

cal diver in the Tec 45 and Tec 50 courses.

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C. Your Obligations and Responsibilities

1. During the Tec 40 course, you have these obligations and responsibilities:

a. To follow the instructor’s directions and dive plans strictly, and to

not separate from the instructor or your dive team.

b. To take all aspects of what you’re learning seriously, and display

an attitude and conduct that is consistent with that expected of a

team-oriented technical diver.

c. To refrain from tec diving outside this course until you’re fully

qualified and certified.

d. To maintain adequate physical and mental health, and to alert the

instructor to any problems you have with them.

e. To accept the risk for this type of diving, and for specific risks

unique to each dive environment, and to immediately notify the

instructor if this risk becomes intolerable for you.

2. Failing to meet these obligations and responsibilities can have these con-

sequences:

a. In the worst case, you could be injured, disabled or killed.

b. You will have failed to demonstrate the attitude and maturity

required for tec diving, and will not qualify for certification.

D. Course Overview, Schedule & Logistics, Administration, Assignments and Study

1. Schedule and logistics [Explain anything that you have yet to cover: the

course schedule, required reading and assignment due dates, sessions,

and training dives. It’s recommended that you have this printed out and

go over it with students when they enroll in the course.]

2. Administration

a. Course costs [Explain and collect, as appropriate, all costs associ-

ated with the course.]

b. Equipment and material requirements [Explain what’s required

for the course, and of that, what students must provide and what

you will provide.]

c. Confirm course prerequisites:

• Students may confirm these with certification cards, log

entries, signed affidavits, etc.

d. Students sign the Tec Diver Statement of Understanding and

Learning Agreement [Discuss what the agreement does not cover,

such as how you will handle missed sessions/dives, assignments

not completed, etc.]

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e. Have student divers read, complete and sign the Liability Release

and Express Assumption of Risk for Technical Diving (or the

technical diving release specified by your PADI Office for your

local area). The release must be signed before any inwater train-

ing. Tec 40 Training Dive One is the exception if participants sign

the standard release used for Discover Tec.

f. Have student divers read, complete and sign the PADI Medical

Statement. Prior to Training Dive Two, the student must have a

physician’s approval and signature on the Medical Statement. If

the student received a physician’s approval and signature on a

Medical Statement for another course within the last year and

has had no medical condition change, and if you have that

Medical Statement on file, then the student does not need to see a

physician again.

g. If students answer “no” to all the medical history questions on

the Medical Statement, they may participate in Tec 40 Training

Dive One. Note that this applies only to Tec 40 Training Dive

One. In some areas, local law requires all scuba participants to

obtain a physician’s approval before any diving.

h. Diver insurance – It’s recommended that you require students in the

DSAT Tec 40 course to have dive accident insurance such as offered

by the Divers Alert Network, if available in your area.]

3. Assignments and Study

[Brief the class on the following points as appropriate for how you will han-

dle knowledge development.]

a. You will study independently with the Tec Deep Diver Manual and

provided handouts.

• The manual supports the entire Tec Diver course – Tec 40

through Tec 50 -- so you’re not required to read all of it at

this level. You also won’t be reading it in order. Much of the

manual pertains to the next, higher levels of technical diving.

• Read the assigned handouts, sections and exercises.

b. You will use the manual to complete knowledge reviews provided to

you. Do not use the knowledge reviews in the manual.

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c. We will review the material and help with anything you

don’t understand [state where/when: class sessions, practi-

cal applications, predive sessions, etc.]

d. You will complete the Tec 40 Exam before the last two

training dives of the course.

II. Technical Diving’s risks and responsibilitiesManual Supported Content

Study assignment: Tec Deep Diver Manual, pgs xi, pg xiii Your

Obligations and Responsibilities, pg xiv Diver Accident Insurance, pg 1-9

including Tec Exercise 1.1. Disregard Tec Deep and Apprentice Tec Diver

Certification Limits discussions. You may skip question 6 in the exercise.

Learning Objectives


1. How do you define recreational scuba diving and technical scuba diving?

2. What is not technical diving?

3. What six general risks and hazards does technical diving present that either

don’t exist, or aren’t as severe, in recreational diving?

4. Why does technical diving, even done “by the book,” pose more risk to you

than recreational diving?

5. With respect to risk, what single statement sums up the difference between rec-

reational diving and technical diving?

6. What risks do you face if you exceed the limits of your training and experience?

7. How could a lack of physical fitness affect you as a technical diver?

8. What are six characteristics of a responsible technical diver?

9. What should you do if you can’t or won’t accept the risks and responsibilities

demanded by technical diving?

A. Recreational diving and technical diving are both for pleasure, but the

terms “recreational diving” and “technical diving” denote important differ-

ences in their limits.

1. Recreational scuba diving is defined as no stop diving with air or

enriched air to a maximum depth of 40 metres/130 feet, and during

penetration dives, within the natural light zone and no more than a

total linear distance of 40 metres/130 feet from the surface.

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2. Technical scuba diving is diving other than conventional commer-

cial or research diving that takes divers beyond recreational diving

limits. It is further defined as and includes one or more of the fol-

lowing: diving beyond 40 metres/130 feet, required stage decom-

pression, diving in an overhead environment beyond 40 linear

metres/130 linear feet of the surface, accelerated decompression,

and/or the use of variable gas mixtures during the dive. Technical

scuba diving uses extensive methodologies, technologies and train-

ing to manage added risk. Typically this means using complex

equipment in situations where direct access to the surface is inac-

cessible due to a ceiling imposed by decompression, or physical

barrier such as that found in cave or a wreck diving environments.

3. Technical diving is not simply exceeding the limits of recreational

diving. Exceeding recreational limits without the appropriate train-

ing, equipment and procedures in place is not technical diving. It is

being stupid and irresponsible.

B. Technical diving poses risks and hazards that are either not present or not

as severe or as likely in recreational diving. These include, but are not

limited to:

1. No direct or immediate access to the surface in an emergency due

to decompression requirements and/or distance.

2. Hypoxia or hyperoxia leading to unresponsiveness and drowning

due to switching to the wrong gas, improper gas choice, or failing

to properly analyze the gas.

3. Narcosis leading to poor judgment, bad decisions or slowed

responses to emergencies.

4. DCS with severe permanent injury, or death. This can result from

higher nitrogen/inert gas loading, improper gas analysis, loss of

decompression gas, being forced to surface without completing

decompression, improper decompression calculation, personal pre-

disposing factors, diving outside the envelope of well documented

decompression theory, and other causes.

5. Omitted procedures and errors caused by extensive equipment task

overloading, leading to accidents from DCS, gas loss, runaway

ascents leading to arterial gas embolism, or barotrauma or oxygen

toxicity caused by runaway descents, etc. The need for redundant

configurations increases the potential for error.

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6. Drowning due to equipment weight and inability to reach the sur-

face due to failed BCD.

C. Although you’ll learn procedures and equipment application to manage the

risks, even when you do everything properly, technical diving poses more

risk than recreational diving, because there are more variables, more

potential hazards, the error chain leading to an accident is short, and sur-

facing in an emergency is (usually) not an option.

1. In recreational diving, if you and your team mate follow all safety

rules and procedures as you’ve been taught, the prob-

ability of a serious accident is very remote.

2. To sum up the difference between recreational and

technical diving risk in a single statement: In techni-

cal diving, even if you do everything right, there is

still a higher inherent potential for an accident lead-

ing to permanent injury and death. You have to

accept this risk if you venture into technical diving.

3. However, the vast majority of accidents in technical

diving, as in recreational diving, result from failing to

apply the proper procedures, failing to have the

required equipment and/or failing to have the

required prerequisite and/or qualifications for the div-

ing being done.

4. Exceeding the limits of your training and experience

poses the risks of severe permanent injury, or death,

due to an accident. Accidents caused by diving beyond limits usu-

ally result from:

a. Diver fails to recognize a hazard.

b. Diver doesn’t know the procedure that prevents or handles

a hazard or emergency.

c. Diver has not practiced a procedure and cannot perform it.

d. Diver executes a procedure improperly.

e. Diver is improperly/inadequately equipped to deal with an

emergency.

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5. Most divers who had accidents when diving beyond the limits of their

training and experience believed, incorrectly, that they could handle

the situation.

D. Physical fitness and tec diving

1. Technical diving places higher physical demands on you than recre-

ational diving. These include, but are not limited to:

a. You must wear and transport heavier equipment - predive,

climbing a boat ladder, etc.

b. You must swim against greater drag, often for extended peri-

ods.

c. Your body systems must deal with higher nitrogen or other

inert gas loads.

d. Heavy exposure suits needed for a dive depth/duration may

pose predive thermal stress due to overheating, particularly in

hot or warm climates.

e. Even with exposure protection, dive duration may pose ther-

mal stress due to chilling.

2. Physical fitness affects whether you will have the performance and

ability needed for technical diving. Like any physical activity, you

must be sure a dive is within your physical capability, with sufficient

physical reserve to deal with emergencies. Most technical dives call

for higher fitness requirements than recreational dives.

a. Your cardiovascular system needs to be able to stand thermal

stresses, carrying heavy equipment, decompression and have

sufficient endurance for high pace swimming against high

drag.

b. You need sufficient skeletal muscle and bone strength to carry

any equipment you need to wear out of the water due to dive

logistics (this can vary with the dive).

c. Lack of the physical fitness required can affect your safety by

limiting your ability to respond to an emergency, or by directly

leading to injuries such as a heart attack, heat exhaustion or

stroke, broken bones or muscle tears due to falling or strain.

d. Only you and your physician can determine your fitness and

assess its suitability for different types of diving. It’s your

responsibility to dive within the limits of your fitness.

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E. Six characteristics denote the responsible technical diver:

1. Self-sufficient. The diver plans and executes each dive as though

having to handle all emergencies alone, and doesn’t rely on any

other diver for safety or knowledge.

2. Team player. The diver is part of the dive team (not just a buddy –

more about this shortly), and contributes as a team player on a

team effort.

3. Disciplined. The diver doesn’t cut corners, bend rules, disregard

dive plans, omit safety equipment or exceed training or equipment

limits.

4. Wary. The diver assumes that everything can and will go wrong on

a dive, and plans contingencies for when it happens.

5. Physically fit. The diver exercises regularly, eats properly and con-

sults a physician regularly to maintain the fitness level required for

the specific dives the diver makes.

6. Accepts responsibility. The diver accepts responsibility for person-

al safety and accepts and acknowledges the risks and demands of

technical diving.

F. You can enjoy a lifetime of exciting, adventurous diving without technical

diving.

1. Technical diving is not for everyone. It is not a goal for all divers

to aspire to.

2. If you cannot or will not accept the responsibilities, risks and

demands required by technical diving, then don’t do it. You will

only endanger yourself and your fellow divers.

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other Delivery Content, Tec 40-1Study assignment: Tec 40 Handout 1

Learning Objectives


1. How do the Tec 40, Tec 45 and Tec 50 courses fit together as the overall DSAT Tec Diver

course?

2. What are the general goals of the Tec 45 and Tec 50 courses?

3. What are the limits of your training as a Tec 40 diver?

G. The DSAT Tec Diver course

1. The Tec 40 course is the first of three subcourses that together make up the

DSAT Tec Diver course.

a. The DSAT Tec Diver course was originally called the Tec Deep Diver

course (hence the Tec Deep Diver Manual).

b. The three subcourses, in order are the Tec 40, Tec 45 and Tec 50

courses. The names reflect the maximum qualification depth in metres

for the respective levels.

c. Completing all three qualifies you as a Tec 50 diver (formerly Tec

Deep Diver), which is a fully qualified, open circuit entry level EANx

deep decompression technical diver.

2. Tec 45 general goals are to train certified Tec 40 divers

a. to use full technical equipment.

b. to make decompression dives to 45 metres/145 feet using air or

enriched air, with accelerated decompression techniques.

c. to dive with one decompression gas with up to and including 100 per-

cent oxygen.

3. Tec 50 general goals are to train certified Tec 45 divers

a. to make decompression dives to 50 metres/165 feet using air or

enriched air, with accelerated decompression techniques.

b. to dive with two decompression gases with up to 100 percent oxygen.

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H. Certification as a Tec 40 diver qualifies you to dive within the following

limits, applying the appropriate procedures and equipment as you’ve been

trained:

1. Dive to a maximum depth of 40 metres/130 feet using air or

enriched air.

2. Make dives with up to 10 minutes required decompression.

3. Use enriched air nitrox with up to 50 percent oxygen (EANx50)

during decompression to make it more conservative.

4. Although your certification qualifies you to these limits, you must

also consider other limitations, such as the environment, conditions

and other factors, and apply more conservative limits when plan-

ning dives.

5. These limits apply, even if you complete the Tec 40 using double

cylinders and other equipment required for Tec 45 and above.

Exercise, other Delivery Content, Tec 40-11. The Tec Diver course (choose all that apply)

o a. consists of three subcourses.

o b. begins with the Tec 40 subcourse.

o c. no longer exists.

2. The Tec 50 course qualifies a diver to make dives

o a. with up to 50 minutes decompression.

o b. with deco stops as deep as 50 feet/12 metres

o c. to a depth of 50 metres/165 feet

o d. to a depth of 50 fathoms (300 feet).

3. As a Tec 40 diver, applying appropriate procedures and equipment as you’ve

been trained, you’re qualified to (choose all that apply)

o a. to dive as deep as 40 metres/130 feet.

o b. have up to 10 minutes required decompression.

o c. use a single gas with up to 50 percent oxygen during decompression.

How did you do?

1. a, b. 2. c. 3. a, b, c.

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II. Tec 40 Equipment requirementsNote to instructor: This section addresses Tec 40 students who will be taking the

course according to the minimum equipment requirements. Students who will

take the course in the full technical rig (Tec 45 requirements) should com-

plete the Equipment study assignments in Tec 45 Knowledge Development

One.


Learning Objectives


1. Why can the equipment requirements for Tec 40 be less stringent than the stan-

dardized technical rig?

2. What are the guidelines for selecting masks, fins and snorkels for the Tec 40

level?

3. What characteristics do you look for cylinders and cylinder valves for the Tec

40 kit?

4. What is the minimum number of fully independent regulators, per diver, and

how do you configure each?

5. What type of BCDs can you use for Tec 40 level diving? Why is a tec diving

harness recommended?

6. How do you choose an appropriate exposure suit for technical diving?

7. What are your options regarding weight systems, and what are the advantages

and disadvantages of each?

8. What types of dive computers and other instruments do you need for Tec 40

level diving?

9. What types of cutting tools are appropriate for deep technical diving, and how

many should you have?

10. What are six general guidelines regarding pockets, accessories and clips you

might need when technical diving?

11. What is a “stage/deco cylinder”?

12. How do you set up a stage/deco cylinder?

13. Why might you need a lift bag/DSMB and reel on a technical dive?

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14. What are suitable lift bags/DSMBs and reels, and how do you secure them on your

rig?

15. What are four recommendations regarding equipment maintenance?

You should also be able to:

16. Describe the layout, arrangement and configuration of the basic Tec 40 rig, with

options, from head to toe as worn by a Tec 40 diver.

A. Tec 40 equipment requirements and the standardized technical rig

1. The technical diving community has a generally accepted open circuit

equipment configuration as worn on a technical deep dive. This standard-

ized technical rig employs all required equipment in a streamlined config-

uration based on a philosophy that minimizes confusion and procedural

error. The standard technical rig (backmount or sidemount) is required at

the Tec 45 level and beyond.

2. You can dive with a less stringent equipment configuration (i.e. the Tec 40

kit or rig) within Tec 40 limits because the depth and decompression time

limits are very restricted compared to broader technical deep diving.

a. Exceeding Tec 40 limits (40 metres/130 feet and up to 10 minutes

total required decompression) is not acceptable or reasonable with

the Tec 40 rig.

B. Mask, fins and snorkel

1. Generally, the mask and fins you use for recreational scuba diving in a

given environment are acceptable for the Tec 40 rig.

a. Full sized fins (appropriate to your size) are generally recommend-

ed.

b. Secure/tape loose straps so they don’t dangle and can’t slip.

c. Spring heel fins (in place of straps) are good options because

they’re very strong, nothing dangles and they don’t need adjust-

ment and are easy to don and remove.

2. Snorkels are optional, but generally recommended for the Tec 40 rig.

a. They allow you to breathe at the surface without using gas from

your cylinder.

b. They can be slightly cumbersome in an air sharing situation, so

you may want to carry a folding/collapsible model in your pocket.

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C. Cylinders and valves

1. You generally want a high capacity cylinder as your primary cylin-

der with the Tec 40 kit. This is because you use more gas on a

deeper dive, and you need to keep a larger reserve.

2. 11-12 litre/71.2-80 cubic foot cylinders are generally considered

the minimum size – larger (18 litre/100 cubic foot+ ) cylinders are

preferred, but not readily available in some locations.

a. If you opt for double cylinders, you should wear the stan-

dardized technical rig, not the Tec 40 kit.

3. The cylinder should have an H or Y valve, which allows you to

have two entirely separate regulators. In case of a failure, you can

shut down the gas to either one and still access the remaining gas

with the other.

a. With Tec 40 limits, it is alternatively acceptable to have a

large, main cylinder with a pony bottle in place of an H/Y

valve.

b. If you use a pony instead of an H/Y valve, it should have a

capacity of 850 litres free gas/30 cf or larger.

c. The pony usually has the same gas (EANx blend or air) as

the main cylinder. If it has a higher oxygen content, the

gas must still be breathable at the deepest planned

depth (max 1.4 ata/bar), with a margin for error.

4. The DIN (Deutche Industrie Norm) threaded system for valve

apertures is generally preferred to the yoke system in tec diving.

5. Valve caps should not be tied to valves as they commonly are in

recreational diving. Remove completely when diving.

D. Regulators

1. Because you cannot immediately surface, tec diving always

requires a minimum of two fully independent regulators per diver

(does not count those on stage or decompression cylinders).

2. Choose top of the line, balanced regulators for maximum reliabili-

ty and performance at depth.

3. Configure the regulator that goes on the right valve post with a

low pressure inflator hose and second stage with a two metre/seven

foot hose.

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4. Configure the regulator that goes on the left valve post with the SPG

and a second stage on a standard length hose (about 80 cm/32 inches). If

using a dry suit or a double bladder BCD system, this regulator also has

a low pressure inflator hose.

a. If using a pony bottle instead of an H valve, both regulators have

SPGs. In this case, the SPGs must be clearly marked or secured

to avoid any confusion.

5. Neither regulator has two second stages.

6. The DIN connection system is preferred (most DIN regulators accept

adapters for yoke use).

E. BCD and harness

1. Most BCDs with shoulder and hip D-rings (other suitable attachment

hardware in those locations) can be used for a Tec 40 rig. The D-rings

are necessary for your decompression cylinder.

2. A tec diving harness configured for a single cylinder is generally recom-

mended, though not essential, for the Tec 40 kit.

a. Tec harnesses are harnesses that mount on top of an interchange-

able BCD bladder. There are rigid plate (steel, aluminum or plas-

tic) and all fabric versions.

b. Tec harnesses have crotch straps, adjustable shoulder and waist

D-rings and other features suited to higher level tec diving.

c. The tec harness is recommended because you will use it when

you move on to the Tec 45 course, and because you can use a

double bladder BCD (BCD with two independent bladders and

inflation/deflation systems) so you have backup buoyancy con-

trol.

• In a decompression situation, simply dropping weights to

restore buoyancy may not be an option because you

would have too much buoyancy to maintain a decom-

pression stop.

• Planning for BCD failure must be part of planning

any technical dive. The double bladder BCD is the

simplest, most reliable option.

• The Tec 40 rig (single cylinder) is not as negatively

buoyant as higher level tec rigs, so redundant buoyancy

is not mandatory at this level.

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F. Exposure suits

1. Choose your exposure suit based on the water temperature at depth

and the dive duration.

2. Tec dives tend to be longer than recreational dives, calling for

more exposure protection. You also don’t exert and generate much

heat while decompressing.

3. Dry suits offer the longest durations and coldest water protection.

a. They may provide ample backup buoyancy.

b. You should master dry suit diving as a recreational diver

before using a dry suit for technical dives.

• 20 dry suit dives is a conservative minimum before

tec diving dry.

• In recreational diving, you only use your dry suit

for buoyancy control while underwater.

• In tec diving, you typically add gas to the suit to

avoid a suit squeeze and use your BCD. This means

controlling the gas in both your suit and BCD – a

more complex skill to master.

4. Wet suits are adequate in warmer waters and well suited to dives

within Tec 40 limits.

a. A full 6 mm/.25 in wet suit with hood will generally handle

dives up to two or three hours (far longer than a Tec 40

dive) in water 24ºC/75ºF or warmer.

b. In a heavy rig, you need a double bladder BCD or other

means for reliably handling a BCD failure.

c. The advantage of a wet suit over a dry suit is operational

simplicity – you only need to adjust your BCD.

G. Weight systems

1. Except in very warm water requiring minimal exposure protection,

you will usually need weights even in a technical rig. A weight

belt, integrated weights or a weight harness are acceptable.

a. Some tec divers choose a metal plate harness to reduce the

amount of lead they need to wear.

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2. Weight belt

a. Advantages: simple, readily available when needed

b. Disadvantages: with crotch strap, must don after putting on

rig so it’s not trapped.

3. Integrated weights

a. Advantages: no need to put on last, positioned amid rig

b. Disadvantages: must have BCD/harness system with weight

system build in; makes overall scuba rig heavier

4. Weight harness

a. Advantages: put on before scuba rig, doesn’t add to rig’s

weight.

b. Disadvantages: may be awkward to adjust rig so it doesn’t

interfere with quick release weight ditching.

5. Loss of weights can be significant hazard on a decompression dive

because it can make it difficult or impossible to stay at stop depth.

a. Some tec divers put two quick release buckles on weight

belts to avoid accidental loss.

b. Another option is to wear a crotch strap over a weight belt

to avoid accidental loss. With this approach, it’s recom-

mended that the crotch strap have a quick release so the

weights can be discarded if necessary.

H. Instrumentation

1. You need two ways of determining your decompression require-

ments.

a. The simplest option is to wear two dive computers.

b. The second option is to wear a computer with depth gauge,

timer and decompression tables.

2. For Tec 40, you only need a standard air dive computer or comput-

ers.

a. An EANx compatible computer is recommended – allows

you to benefit from more bottom time with enriched air,

and calculates your oxygen exposure.

b. If you have yet to invest in your dive computers, choose

models that run multiple gases and trimix so you’ll be set

for Tec 45 and beyond.

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3. Arm mounted instruments (other than SPG) are generally preferred

(required at the Tec 45 level and up).

4. Mechanical SPGs are generally preferred because they’re simple and reli-

able.

5. Compass – You need a high quality, liquid filled model if using a standard

compass. Many newer dive computers have electronic compasses. The

compass is commonly carried in a pouch or pocket until needed.

I. Cutting tools

1. You should have a cutting tool, and ideally two (two required at Tec 45

level up). Mount at least one where you can reach it with either hand

(generally waist/chest area).

2. Typical dive knife, dive shears, Z-knife (hook with blade), stainless fold-

ing knives and dive tools are all acceptable.

3. Large, calf-mounted knives/tools are generally avoided in tec diving, espe-

cially cave diving and wreck penetration, because they entangle easily.

J. Guidelines for pockets, accessories and clips

1. Avoid large pocket pouches on harnesses – they cause too much bulk and

clutter.

2. Most useful pockets in tec diving are thigh pockets on your exposure suit.

3. Mount stainless steel or brass clips on accessories to clip to your BCD or

harness. Don’t mount the clips on the BCD or harness.

4. Sliding gate clips (a.k.a. dog clips) are preferred to marine snaps (swing-

ing gate clips), because they won’t accidentally clip to things by them-

selves.

5. Choose clips based on the environment – you need larger clips when

wearing thick gloves.

6. Using and mounting clips

a. When possible, keep accessories in pockets until needed.

b. Clip accessories well out of the way, secured so they don’t dangle.

c. Attach clips so they can break away so you can release in an emer-

gency. The simplest approach is to mount the clip via a small

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o-ring or thin pull tie that breaks with a sharp tug.

K. Stage/deco cylinders

1. A stage cylinder is used to extend the deep portion of the dive. A

deco (decompression) cylinder provides gas (usually with higher

oxygen content) during decompression. They are rigged the same,

so it’s common to call deco cylinders “stages” or “stage cylinders.”

The general term for both is “stage/deco cylinder.” In context, the

terms are seldom confusing.

2. Stage/deco cylinders are worn on the side under the arm, clipped at

the waist and on the chest.

3. A stage/deco cylinder never replaces one of the two regulators/

valves you need from your primary gas supply.

4. As a Tec 40 diver, you will often use a deco cylinder.

a. Some dives at this level do not need a deco cylinder,

because you have enough gas, plus your required reserve,

for the entire dive including decompression.

b. But, a deco cylinder is recommended nonetheless because it

provides extra gas capacity, plus gives you the option of

switching to EANx with a higher oxygen content for added

decompression conservatism. (More about this later).

5. Typical stage/deco cylinder setup

a. The cylinder is typically a 4 litre/30 cf size or larger. The

popular aluminum 11 litre/80 cf has more capacity than you

usually need at the Tec 40 level, but it is commonly avail-

able and easy to handle. It is perfectly acceptable to use –

having too much gas is seldom an issue.

b. The cylinder has a nylon rope/strap approximately 46

cm/18 in, approximately under the valve opening, running

down to a band around the cylinder with a clip at each end.

This serves as a handling strap; the clips attach the cylinder

on your BCD D-rings at the waist and chest/shoulder.

c. The regulator has a single second stage and SPG. Hoses

tuck under inner tubing, bungee or stretch nylon straps

around cylinder.

d. The second stage has break-away clip usually attached to

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the hose close to where it meets the second stage.

e. The SPG may have a very short hose, or a standard length

hose that is tucked along the cylinder length.

f. It’s recommended that the clips be attached via rope or

nylon so you can cut the cylinder free if a clip jams.

g. For safety, stage/deco cylinders are always clearly

marked with the gas blend they contain, the maximum

depth you can breathe the gas (based on the oxygen

partial pressure) and the diver’s name. These markings

are always large and positioned so a team mate can

read them while the cylinder is worn.

L. Lift bags/DSMBs (Delayed Surface Marker Buoys) and reels

1. You may find yourself accidentally away from your planned ascent

line (anchor/mooring line).

2. In this case, your team uses a reel to deploy a lift bag or DSMB.

This gives you an ascent reference, allows surface support person-

nel to track your position, and helps you maintain your decompres-

sion stop in midwater.

3. Suitable lift bags are brightly colored, with large capacities (45

kg/100 lbs lift) preferred. DSMBs are taller and more compact;

they don’t have to have the same lift capacities. Preferred DSMBs

have one-way valves for filling, with overpressure valves. These

keep the buoy inflated even if it topples at the surface momentari-

ly. It is recommended that you write your name on your lift bag/

DSMB for surface support identification.

4. Lift bags are carried rolled up and tucked into special carrying

pockets or put in bungees that stow them horizontally in the small

of the back. DSMBs roll up more compactly, generally, and fit in

harness/BCD pockets or thigh pockets.

5. A suitable reel is compact with ample line to reach the surface.

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6. The reel is clipped to a D-ring on the right hip.

M. Maintenance

1. You rely on your gear for life support. Therefore, maintain it

according to manufacturer recommendations.

2. Have regulators, valves, BCDs and gauges inspected and over-

hauled at least annually, or more frequently for heavy use or as

manufacturer specified.

3. Have anything that doesn’t appear to work normally serviced

before using it.

4. Never tec dive with gear in anything but top shape and within its

design parameters. To do otherwise needlessly raises your risk of

injury or death by starting the dive with a potential problem.

N. Putting it together: basic Tec 40 rig, head to toe

1. Use a cylinder with H or Y valve in a BCD/tec harness.

2. The left side regulator has a short hose second stage. This is the

secondary regulator. It routes to the right and hangs below the chin

on a bungee. The SPG hose goes down along the cylinder; the SPG

has a clip to secure it to waist or chest D-ring (as preferred). Low

pressure hose(s) feeds the dry suit and/or backup BCD (if used).

The valve is open all the way (do not close it back a quarter turn).

3. The right side regulator has a long hose second stage. This is the

primary regulator. It is the last thing you put in place when kitting

up. The hose routes straight down along the cylinder to the hip,

then up across the chest and around the left side of the neck into

the mouth. At the hip, the safety reel lies on top of it to help keep it

in place. The low pressure hose feeds the primary BCD inflator.

There is no SPG. The valve is open all the way (do not close it

back a quarter turn).

4. If using a pony instead of an H/Y valve, the pony goes on the left

side of the main cylinder and takes the left side (secondary) regula-

tor. In this case, the right (primary) regulator has the primary SPG,

which is clipped as described above. The pony/secondary SPG is

clipped low and behind the diver, where it is retrievable but not

easily confused with the primary. It is also clearly marked (label,

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color, etc.) to easily distinguish it from the primary SPG.

5. With double bladder BCDs, the backup inflator is secured behind

the diver so that it is easy to deploy, but not easily confused with

the primary (you only use one BCD bladder at a time).

a. Some divers leave the LP hose disconnected from, but bun-

geed to the backup inflator. This avoids accidental inflation

(leaking inflator valve), but is easily connected for use.

6. Instruments are ideally arm mounted (except SPG), though com-

pact consoles are acceptable in the Tec 40 rig.

7. The weight system is secure, free for ditching. The backup buckle

is secured if used.

8. Mask and fins are preadjusted and inspected, secured so they can’t

slip out of adjustment.

Exercise, Other Delivery Content, Tec 40-2

1. Tec 40 has less stringent equipment requirements than the standardized techni-

cal rig, because the limits of Tec 40 diving keep you within recreational depth

limits and a relatively short decompression time.

o True

o False

2. You cannot use the same fins you use in recreational diving for Tec 40 diving.

o True

o False

3. The recommended valve type for the Tec 40 kit is

o a. the standard yoke valve.

o b. a J reserve valve.

o c. an H or Y valve, DIN system.

o d. a J or K valve, yoke system.

4. The minimum number of fully independent regulators, per diver, is

o a. 1

o b. 2

o c. 3

o d. 6

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5. You can use any BCD with D-rings or attachment hardware at the shoulder/

waist for the Tec 40 kit.

o True

o False

6. Choose an exposure suit for a tec dive based on __________. (choose all that

apply)

o a. depth

o b. duration

o c. temperature

o d. activity level

7. You never use a weight belt while tec diving.

o True

o False

8. For the Tec 40 level, a single computer is all the instrumentation you need.

o True

o False

9. At the Tec 40 level, you should have at least one cutting tool, but it’s recom-

mended you have two.

o True

o False

10. General guidelines regarding pockets, accessories and clips include (check all

that apply):

o a. mount clips to the accessories.

o b. attach clips so they can break away.

o c. thigh pockets on your exposure suit are a good option.

o d. marine (swing gate) clips are the best choice.

11. At the Tec 40 level, a stage/deco cylinder will be used to

o a. carry a decompression gas.

o b. carry gas to extend the deepest portion of the dive.

o c. both a or b.

o d. None of the above.

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12. A stage/deco cylinder is always marked with the gas it has in it, the maximum depth

and the diver’s name.

o True

o False

13. You may need a lift bag/DSMB and reel

o a. as a backup BCD.

o b. in case you lose track of your ascent point.

o c. to open a shipwreck hatch

14. A suitable lift bag or DSMB should have ample lift and be blue or gray.

o True

o False

15. Never, ever tec dive with gear that’s in anything less than top shape.

o True

o False

16. The primary regulator (choose all that apply)

o a. goes on the right.

o b. has a long hose second stage.

o c. has the primary BCD low pressure hose.

o d. goes on the left.

How did you do?

1. True. 2. False. The same fins you use recreational diving are usually suitable for the

Tec 40 level. 3. c. 4. b. 5. True. 6. a, b, c, d. 7. False. A weight belt is a common option

in tec diving. 8. False. You need at least two computers, or one computer and a depth

gauge, timer and decompression tables. You should also have SPGs and a compass. 9.

True. 10. a, b, c. 11. a. 12. True. 13. b. 14. False. It should be red, yellow or some other

bright color. 15. True. 16. a, b, c.

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Manual Supported ContentStudy assignment: Tec Deep Diver Manual, pgs 84-87, Oxygen Compatibility

Review, Manufacturer Warranties and Hyperoxic Gases

Learning Objectives


1. What are the guidelines regarding material and equipment compatibility using enriched

air with more than 40 percent oxygen?

O. Oxygen compatibility review

1. As you recall from your Enriched Air Diver course, using gas blends with

more than 21 percent oxygen calls for special equipment considerations to

avoid fire and/or explosion hazards.

a. As a Tec 40 diver, you will be qualified to use EANx up to and

including 50 percent oxygen – the higher the oxygen content, the

more important this issue is.

2. Any equipment (regulator, valve, cylinder) that will be exposed to a gas

with more than 40 percent oxygen, or pure oxygen, at any time (including

during blending) must be rated for oxygen service.

a. It must be oxygen clean – free of contaminants.

b. It must be oxygen compatible – made from materials that don’t

combust easily in oxygen.

3. Follow manufacturer recommendations regarding use with air, enriched air

or oxygen. Some manufacturers require oxygen service for any enriched

air, and some limit the oxygen percentage. However, you may have to

make some compromises. [Provide updated information on the oxygen

compatibility issue as available.] [See Note to Students.]

4. If you expose oxygen service equipment to nonoxygen clean gases or other

contaminants, the equipment is no longer oxygen clean or oxygen service

rated.

a. Example: Using an oxygen service regulator on a standard air cylin-

der – the regulator is considered contaminated.

b. Example: Filling an oxygen service cylinder from a standard scuba

air source – standard scuba air (Grade E) is not oxygen clean, and

the cylinder must then be re oxygen cleaned. (In the U.S. you must

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use Grade E Modified or Grade J).

5. Leave enriched air cylinder tags in place for removal by blender – this allows

blender to confirm that the cylinder was not refilled by nonoxygen clean air

source.

6. To minimize the heat of compression, open cylinder valves slowly and allow

equipment to pressurize slowly when using enriched air and oxygen.

7. Protect oxygen service equipment from contamination by keeping it bagged and

sealed from the environment until needed. Rinse and stow oxygen service equip-

ment as soon as possible after use, and keep it away from areas or exhaust that

may have oil or other contamination.

8. The general guideline is to have oxygen service equipment recleaned annually.

9. Violating guidelines regarding oxygen compatibility carries a severe risk of injury

and/or property damage caused by fire and/or explosion.

Note to Students: [Read this to student divers if the DSAT Tec Deep Diver Manual is not in a language they can understand.[ You’re learning to use enriched air nitrox with more than 40 percent oxygen and/or pure oxygen to extend no stop time and benefit decompression. Their use verges on the essential for decompression after long, deep dives. The use of higher oxygen probably lessens the risk of de-compression sickness, because it is generally believed that for a given a decompression model, a schedule requiring shorter stops is more reliable than a schedule requiring longer stops. Without the high oxygen, you’d face impractically long decompression stops. Therefore, when a diver can get out of the water quicker (accelerated decompression), it reduces the exposure to others risks as diverse as marine predators, hypothermia, getting separated from the boat in strong currents, and so on. Technical diving is undoubtedly safer with the use of high oxygen gases than it would be without them, which is why it is a standard practice in the tec diving community. Using hyperoxic gases, however, is not without some risk and controversy. Outside of issues you’ve learned related to central nervous system and pulmonary oxygen toxicity, the greatest hazard comes from the risk of fire. That’s why, as you’ve learned, any high pressure device coming in contact with a gas with more than 40 percent oxygen (or less than 40 percent if specified by the manufacturer) must be cleaned and dedicated for use with pure oxygen. That’s easy to say, but not as easily done.At this writing, relatively few equipment manufacturers in the dive industry warrant the use of any of their equipment with pure oxygen. A few do, but others specifically warn against using their equipment with enriched air nitrox mixtures containing greater than 40 percent oxygen. Yet, you will still learn in this course to use proper oxygen service equipment with hyperoxic gases includ-ing pure oxygen.

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Basically it comes down to balancing the risks: the risk of getting seriously hurt or killed due to decompression sickness against the risk of getting seriously hurt or killed due to fire or explosion. Most tec divers believe – and accident data sup-port – that provided you’re using properly cleaned and compatible equipment, not using oxygen is a far greater risk than using it. In fact, while plenty of divers have been bent over the years, as of this writing only a handful – perhaps only one or two -- has been seriously injured as a result of an oxygen fire using a hyperoxic gas in a technical scuba diving context. And, that is in the context of tens of thou-sands of dives (at least) made with such mixtures over the past decade.In the end the choice will be yours. If you decide to stick with the strict manufac-turer’s guidelines for your regulators, tanks, valves, and SPGs, you may have to choose decompression gases with no more than 40 percent oxygen. But if so, you must then be willing to accept the risks attendant to the lengthier decompression times involved. Most of the technical diving community believes that, the manufacturers’ warnings notwithstanding, you are better off in technical diving to use oxygen and other hyperoxic mixes than not. The risk of fire and explosion is real and is, yet again, another risk you must personally assume before getting involved in techni-cal diving. To manage and minimize that risk, be certain that any equipment you will use with a gas with more than 40 percent oxygen has been serviced for that use by a qualified professional.

III. Gas Planning – EAD review, oxygen limits, SAC and gas supply requirements, oxygen toxicity and exposure

Manual Supported ContentStudy assignment: Tec Deep Diver Manual, pgs 35-50, Gas Planning I,

Tec Exercise 1.3

Learning Objectives


1. What is an Equivalent Air Depth (EAD) and how do you find it?

2. What are the maximum recommended oxygen partial pressures for deep techni-

cal diving?

3. What determines the maximum depth to which you can use an enriched air

blend during the working (bottom) phase of the dive?

4. What determines the maximum depth to which you can use an enriched air

blend during the decompression/safety stop phase of a dive?

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5. How do you find your Surface Air Consumption (SAC) rate?

6. How do you use your SAC rate to estimate your gas supply requirements

for a given depth and time?

7. How do you determine your reserve gas supply ?

8. How do you determine how much gas a cylinder has?

9. What are CNS oxygen toxicity and pulmonary oxygen toxicity, and what causes each?

10. What are the signs and symptoms of CNS oxygen toxicity?

11. What are the signs and symptoms of pulmonary oxygen toxicity?

12. What is the so-called “CNS clock”?

13. What are Oxygen Tolerance Units (OTUs)?

14. What methods do you use for managing oxygen exposure?

15. What is the primary way you avoid CNS oxygen toxicity while diving

with air, enriched air or pure oxygen?

A. Equivalent Air Depth (EAD)

1. As you recall, the EAD is an adjusted depth on air tables when diving with

EANx.

2. EANx has less nitrogen than air; therefore the EAD is less than the actual

depth.

3. You find the EAD by:

a. using formulas [write out for students]

b. Looking it up on tables such as the DSAT Equivalent Air Depth Table

or the Equivalent Air Depth and Oxygen Management Table found in

the Tec Deep Diver Manual Appendix. Remember to express the frac-

tion of oxygen as a decimal; e.g. 32% oxygen, use .32.

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c. Using desk top decompression software like you’ll be applying in this

course. [Intro this only – software will be covered in more detail later.]

[With the class, use tables or formulas to find several EADs for depths to

40 metres/130 feet using various blends. This is primarily a review/update

from recreational enriched air training.]

4. Enriched air dive computers automatically determine EADs in their calculations.

B. Maximum depth

1. As you recall, in recreational enriched air diving, the maximum oxygen partial

pressure (PO2) is 1.4 ata/bar.

2. Technical diving uses the same limit for the bottom or working part of dive.

a. The maximum depth to which you can use an EANx blend or oxygen added

during the decompression phase comes from the depth at which you reach a

PO2 of 1.6 ata/bar (contingency maximum in recreational enriched air div-

ing).

b. Limiting your PO2 to a more conservative limit is a good idea when possi-

ble, especially if you may have to exert yourself during decompression (due

to current, etc.)

c. Note to imperial system divers: The PO2 of pure oxygen at 20 feet of sea-

water is 1.61 – the .01 difference is ignored because it’s physiologically

insignificant, and the depth difference is less than 3 inches. Although you

won’t use pure oxygen at the Tec 40 level, higher level tec divers routinely

use oxygen at 20 feet.

3. As with the EADs, you find your PO2s and maximum depths by:

a. Using formulas.

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b. Looking them up on tables such as the DSAT Equivalent Air Depth Table or

the Maximum Depths Table found in the Appendix of the Tec Deep Diver

Manual (formulas are in the Appendix, too.)

c. Using desk top decompression software like you’ll be applying in this course.

[Go through one or two problems to find PO2s at different depths and maxi-

mum working phase and decompression phase depths, for different blends for-

mulas. Then use the tables, which is the simplest and most practical method.]

C. Gas consumption

1. In this course, you’ll learn to plan gas use based on how fast you consume it.

a. Your Surface Air Consumption (SAC) rate is the rate you use gas (in litres or

cubic feet per minute) if swimming at a moderate speed in all your equipment

at the surface.

b. SAC changes with equipment and anything else affecting drag.

c. SAC changes as you gain skill and fitness, and with physical variables such as

temperature.

d. SAC can be expressed in bar/psi per minute, or gas volume per minute.

e. You’ll also hear references to Respiratory Minute Volume (RMV), and it is

often the term used in decompression software. The medical community

defines RMV as:

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RMV = Vt -Vd x respiratory ratewhere Vt = tidal volume, Vd = respiratory dead air space and respi-ratory rate = breaths per minute.

• Tec divers sometimes use RMV to mean SAC rate based on

volume – this is not technically accurate, but close enough.

• You’ll hear SAC rate and RMV used interchangeably; this is

fine, but do not confuse SAC rate based on bar/psi with

SAC rate based on volume. They’re not the same thing.

2. Finding your SAC rate – use this formula:

[Make up other examples and work through them until you’re confident students

understand and can apply the formula.] Emphasis Note to Students Sometimes SAC is determined as bar or psi in-stead of volume per minute. This isn’t useful in technical diving because bar/psi per minute depends upon the specific cylinder type.

3. You may want to determine your SAC rate at rest for decompression/safety

stop planning, so you will know both your working SAC rate and your decompres-

sion SAC rate.

4. You need to adjust your SAC rate up or down based on your expected exer-

tion during the dive. When in doubt, estimate upward.

5. As you gain experience, your SAC rate tends to get smaller; check periodi-

cally and when making substantial equipment changes.

6. Estimating your gas requirements for a given depth:

a. You’ll use your SAC rate to estimate gas supply requirements. At

the Tec 40 level you will do this by entering your SAC rate into

decompression software, which calculates your gas supplies for

you. But, you should know how it is calculated so you can recog-

nize should your software be off (usually due to entry errors).

b. To determine your estimated gas supply requirement for a given

depth:

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[Go through several examples until you’re confident students

understand and can apply the concept.]

7. Reserve

a. Since gas supplies are estimates, to allow for the unforeseen, you

always plan a reserve. The most common reserve for technical div-

ing is 33 percent (“thirds” or “rule of thirds”). This means 33 percent

of your supply is purely for contingency use. The higher the percent,

the more reserve.

b. To determine your gas requirements with reserve, use this formula:

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or

gas required ÷ .66 = total gas

D. Actual gas supply

1. Once you know how much gas you need, you also need to know how much

gas you have when you start the dive. Note that while software will calcu-

late how much gas you need, there are not many programs that calculate

how much you have – you have to do it. To do so, you calculate the vol-

ume based on the pressure. How you do this varies slightly with the metric

and imperial systems.

2. Metric system: Cylinders are designated by their nonpressurized internal

volume in litres. Simply multiply the designated volume by the pressure in

bar; for doubles, multiply that by two:

Example: An 11 litre cylinder has 185 bar in it. What is the available gas

supply?

Answer: 2035 litres. (11 x 185 = 2035 litres).

3. Imperial system: Cylinders are designated by their capacity in cubic feet at

their working pressure.

a. One way to find gas supply is to divide the actual pressure by the

working pressure and multiply that by the designated capacity.

(A/W x C = cubic feet)

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Example: An 80 cubic foot cylinder, working pressure 3000

psi, has 2500 psi in it. What is the available gas supply?

Answer: 66.6 cubic feet. (2500 ÷ 3000 = .83, .83 x 80 =

66.6 cubic feet)

b. Another, more popular way is the baseline method. A base-

line is how many cubic feet cylinders hold per psi, which

you multiply by the actual psi.

• To get the baseline, divide the designated capacity

by the working pressure. Then multiply the result

by the actual pressure.

Example: An 80 cubic foot cylinder, working pressure 3000

psi, has 2500 psi in it. What is the available gas supply?

Answer: 66.8 cubic feet. (To get the baseline: 80 ÷ 3000 =

.0267; .0267 x 2500 = 66.8) Note the slight difference with

the previous example due to rounding.

Example: A set of double 80 cubic foot cylinders, working

pressure 3000 psi, have 1850 psi in them. What is the avail-

able gas supply? Answer: 132.5 cubic feet. (To get the

baseline: 80 x 2 ÷ 3000 = .053; .053 x 1850 = 98.05)

• The advantage of the baseline method is that you

can determine the baselines for the cylinders you

use frequently and record them in your log book.

Then you only have to multiply the cylinder base-

line by your SPG reading to determine the gas vol-

ume you have.

4. Keep in mind that the popular designation may be rounded.

(Example, some types of the imperial system aluminum “80” actu-

ally hold 78.2 cubic feet at the working pressure). This normally

isn’t a huge issue, but may be if your required gas supply and sup-

ply available are very close.

5. If you find your gas supply available isn’t adequate for the dive

you’ve planned, you need to recalculate a shorter dive, or get more

gas to cover the dive.

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E. Oxygen toxicity

1. You recall that exposure to high oxygen partial pressures can cause Central

Nervous System (CNS) oxygen toxicity and pulmonary oxygen toxicity.

2. Unacceptable risk of CNS toxicity results from an exposure to a PO2 above

1.4 ata/bar during the working phase of the dive and 1.6 ata/bar during the

resting/decompression phase.

a. The primary symptom/sign is a convulsion, which can cause drown-

ing underwater.

b. Warning signs/symptoms usually do not precede a convulsion, but if

they do, include visual disturbances, ear ringing or sounds, nausea,

twitching in facial muscles, irritability and restlessness, and dizzi-

ness. (Remember VENTID - vision, ears, nausea, twitching, irritabil-

ity, dizziness)

c. You must accept the risk that, under rare circumstances, CNS oxygen

toxicity can occur at lower PO2s than 1.4/1.6.

d. Although your risk diminishes when you drop your PO2, you can

still have a convulsion after ascending or switching to a gas with less

oxygen.

3. Pulmonary toxicity results from long term exposure to PO2s above .5 ata. It

is not immediately life threatening.

a. Signs/symptoms include lung irritation, a burning sensation in the

chest, coughing and reduced vital capacity.

b. Although highly unlikely in recreational enriched air diving, pulmo-

nary toxicity is possible in technical diving, especially after using

oxygen for decompression.

F. Managing oxygen exposure

1. You manage oxygen exposure to avoid both forms of oxygen toxicity.

2. The DSAT Oxygen Exposure Table and other variations on the “CNS clock”

are one way to manage pulmonary toxicity.

a. It is based on allocating exposure as a percentage of the maximum

allowed by NOAA oxygen limits. (See the Oxygen Limits Table in

the Appendix of the Tec Deep Diver Manual.)

b. It is misnamed the “CNS clock” because the methodology was

thought (somewhat inaccurately) to manage CNS exposure. Actually,

it primarily manages pulmonary oxygen toxicity.

c. You’ll learn more about using the CNS “clock” in the Tec 45 and Tec

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50 courses. Provided you keep your PO2 above 1.4 bot-

tom/1.6 deco, oxygen toxicity is highly unlikely within Tec

40 dive limits.

3. Oxygen Tolerance Units (OTUs) also manage pulmonary toxicity.

a. OTUs are dose units of oxygen assigned based on daily

exposures and cumulative exposures.

b. You’ll learn more about OTUs and using them in the Tec

45 and Tec 50 courses.

4. Whether using air, enriched air or oxygen, the primary methods for

tracking pulmonary toxicity-related oxygen exposure are:

a. OTUs/CNS clock by using tables and formulas (more about

these in the Tec 45 and Tec 50 courses).

b. OTUs/CNS clock automatically tracked by a dive computer

(far more practical – one way you will track oxygen expo-

sure as a Tec 40 diver).

c. OTUs/CNS clock automatically calculated by decompres-

sion software (more practical, and useful for planning dives

with dive computers – you will also do this as a Tec 40

diver).

5. Whether using air, enriched air or oxygen, the primary method for

managing CNS toxicity related oxygen exposure is to keep your

PO2 at or less than 1.4 ata/bar (working or bottom phase) or 1.6

ata/bar (decompression/safety stop phase).

a. CNS toxicity is very unpredictable when a diver exceeds 1.4

- 1.6 ata/bar PO2. Because there are too many strong phys-

iological variables, there is not a useful relationship

between exposure and partial pressure. The same diver can

have no problems at high PO2 for hours one dive, and con-

vulse in minutes at a lower PO2 in another.

b. Stay well within limits – there’s generally no real dive time

benefit or decompression advantage of pushing them.

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G. The Equivalent Air Depth and Oxygen Management Tables in the Appendix of the

Tec Deep Diver Manual list EADs, PO2s, “CNS clock” percent per minute and

OTU per minute for 21 percent oxygen through pure oxygen. You will not need to

use these as a Tec 40 diver, but you should be beginning to understand why these

concepts are increasingly important as you dive deeper and make longer decom-

pressions using gases with up to 100 percent oxygen.


Learning Objectives


1. What is the maximum oxygen blend you would use as the bottom gas for a dive to 40

metres/130 feet?

2. What is the maximum percentage of oxygen you will use as a Tec 40 diver?

H. As a Tec 40 diver, your maximum allowable depth is 40 metres/130 feet.

1. Using the maximum depth tables on pages 266 and 267, you find that

EANx28 is the highest oxygen content gas blend you can use at 40

metres/130 feet (PO2 = 1.4 ata/bar).

2. You may use blends with more oxygen, but at increasingly shallower maxi-

mum depths.

3. With blends that have 36 percent or more oxygen, your maximum depth is

so shallow and your no decompression time is so long that you probably

won’t have to make decompression dives at all.

I. The maximum oxygen percentage you’re qualified to use as a Tec 40 diver is 50

percent (EANx50). You will normally use this as a decompression gas (you can use

it as a bottom gas, but the maximum depth is 18 metres/59 feet – you will probably

not need to decompress on such a dive).

1. The maximum depth for using EANx50 as a decompression gas (PO2 = 1.6)

is 21m/70 ft (See the Equivalent Air Depth and Oxygen Management Tables

for 50% on pgs 274 & 288).

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2. You may be carrying EANx50 (or other deco gas) to a depth deeper than

you can safely breathe it. It is critical to follow all gas handling proce-

dures to avoid accidentally switching to it at too deep a depth. You

will learn and practice these procedures beginning with Tec 40 Training

Dive One.

Exercise, Other Delivery Content, Tec 40-3

1. The maximum oxygen enriched air you would use as bottom gas for a dive to 40

metres/130 feet is

o a. EANx28.

o b. EANx32.

o c. EANx36.

o d. EANx50.

2. The maximum oxygen content enriched air that you’re qualified to use as a Tec 40

diver is

o a. EANx28.

o b. EANx32.

o c. EANx36.

o d. EANx50.

How did you do?

1. a. 2. d.

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IV. Team DivingManual Supported Content

Study assignment: Tec Deep Diver Manual, pgs 51-54, Team Diving I, Tec Exercise

1.4

Learning Objectives


1. What is meant by “team diving”?

2. What are four benefits of team diving?

3. What are your responsibilities as a team member when technical diving?

4. What is the rule regarding aborting a technical dive?

A. The team concept

1. Technical diving employs the team diving concept. Team diving is the

buddy system taken to the next emphasis level.

2. The team diving philosophy is that technical divers work as a team with

focus on integrating team members’ needs and efforts during predive checks,

meeting equipment requirements, planning and executing the dive, and other

details. Team diving treats the dive as a mission with a specific purpose the

team pursues together with a common goal, rather than as just an underwa-

ter visit.

B. Team benefits include:

1. higher likelihood of mission success based on detailed dive planning.

2. preparedness and resources for handling complex emergencies.

3. accident reduction by being each other’s “back up brains” during predive

checks and throughout the dive.

4. the camaraderie that comes from facing a challenge together.

C. As a team diver, you have responsibilities:

1. Be self sufficient, even in an emergency. You plan your dives so you can

respond to emergencies independently; your team mates may make it easier

and provide a Plan B if necessary, but not as your primary responses to an

emergency.

2. Don’t let the team carry you beyond your limits. Otherwise, you can’t stay

self sufficient.

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3. Watch your team mates as closely as you watch yourself. After you

check your gear, check their gear. After confirming what gas

you’re breathing, confirm what gas they’re breathing, etc.

4. When necessary, surrender your individual preferences to the team

needs. As you’ll learn, for example, generally all team members

dive with the same gases. You may prefer a different blend for a

specific dive, but team unity may be more important. If you ever

feel such a team choice compromises safety, it’s your responsibili-

ty to decline the dive.

5. Do not exert peer pressure, and do not succumb to peer pressure.

All team members need to be confident about their ability to suc-

cessfully perform the dive.

D. Team size– what is the “right” size for a team?

1. Preferred size varies with the divers, dive objective and other vari-

ables, but is typically two to four divers, not counting support div-

ers (when present).

2. Many tec divers think of three divers as an optimum number in

many circumstances, because in the event a team member has a

problem, it provides two divers to assist the one.

3. However, this is not a “rule” or “standard.” Two divers and more

than three are also common team sizes, and work effectively.

4. On some projects, the “team” may be very large – 10 to 15 divers

working toward a common goal – though this is usually composed

of smaller subteams of two or three to make things manageable.

E. To negate peer pressure effects, all responsible technical divers adhere to

and honor a rule that originated with cave diving: Any diver can abort

any dive at any time for any reason.

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V. Techniques and ProceduresManual Supported Content

Study assignment: Tec Deep Diver Manual, pgs 54-59, Techniques and Procedures

I, Tec Exercise 1.5, pgs 107-109, Team Diving Gas Handling Considerations, Tec

Exercise 2.4 questions 4-8, pgs 115-122, Techniques and Procedures III, Tec

Exercise 2.5

Learning Objectives


1. What general elements does a technical diving predive check cover?

2. How do you determine the minimum weight you need for a technical dive?

3. What is the primary hazard of diving negatively buoyant, and how do you manage this

hazard?

4. What is the primary hazard of excessive positive buoyancy, and how do you manage this

hazard?

5. How do you determine the minimum buoyancy you need on a technical dive?

6. What are the techniques for using a dry suit and BCD?

7. What is the technique for using a redundant (double bladder) BCD?

8. What is a descent check and when do you do it?

9. Why do all team members on a technical dive usually use the same gases?

10. What four markings should on every cylinder used in a technical dive?

11. What cylinder markings should be easily read by your team mates while wearing the

cylinder?

12. Why must the cylinders be marked as described?

13. Who must check the pressure and oxygen analysis of every cylinder used in a technical

dive?

14. What is the most important skill you need for decompressing and why?

15. When decompressing, what is the ideal body position and where should you put your

stop depth in relation to your body?

16. What is the proper ascent rate on a decompression dive?

17. What is the procedure for putting on a stage/deco cylinder?

18. In what order should you stack stage/deco cylinders?

19. What is the procedure for removing and leaving a stage/deco cylinder?

20. What is one of the most preventable causes of death in technical diving?

21. What are five guidelines that reduce the chance of accidentally switching to an unsafe

gas blend at depth?

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23. What is the procedure for switching gases underwater?

23. What is the recall acronym for gas switching, and what does it stand for?

[Note to instructor: To avoid confusion, the objectives and outline below follow the sequence

of the content as found in the Tec Deep Diver Manual.]

A. As in recreational diving, you begin a technical dive with a predive check. It’s simi-

lar to the one you perform in recreational diving, only more extensive. (Get in the

habit of using a preprinted checklist, such as on the TecRec Dive Planning

Checklist.) You’ll learn and practice it in detail later, but in general the team covers

these elements:

1. All equipment and back up equipment set up and functioning.

2. Gas supplies – contents, quantities and proper marking.

3. Decompression status monitoring– computers/tables and back ups, and their

compatibility.

4. Equipment rigging and configuration – all secure, properly located and rout-

ed, all team members know where to find each other’s gear.

B. Buoyancy and weighting for technical diving

1. You weight yourself so you can stay at 5 metres/15 feet with a near empty

cylinder (for Tec 40) or doubles and no stage/deco cylinders. This would be

the worst-case during a decompression dive.

2. You find your weight by wearing all your gear and doing a conventional

buoyancy check with 35 bar/500 psi or less in your cylinder(s). Weight your-

self so you float at eye level, or slightly sink. This is the minimum for that

gear configuration.

3. With the heavy cylinders and in warm water that requires minimal thermal

protection, you may be negatively buoyant even with no weight on. This is

acceptable; you don’t need any more weight.

4. With full cylinders, you may be substantially heavier. A single will be as

much as 3.5 kg/7.5 lbs heavier, and doubles than 7 kg/15 lbs. Full stage/

decompression cylinder(s) add even more weight.

a. The primary hazard of diving negatively buoyant is having a BCD

failure that makes it effectively impossible to ascend.

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b. This is not usually an issue in a Tec 40 rig unless you’re wearing

very little buoyant thermal protection. It is, however, commonly a

concern with heavy double cylinders.

c. You manage this by having more than one way of regaining buoyan-

cy control:

• Redundant BCD (two bladders)

• BCD and dry suit.

• For the heaviest diving, a dry suit may not supply sufficient

buoyancy, and you may need a redundant BCD even with the

dry suit.

5. The primary hazard of positive buoyancy is the inability to make required

decompression stops, and/or a rapid ascent, leading to a high risk of decom-

pression illness. You manage this risk by:

a. checking your weight with near-empty cylinders so that you’re ade-

quately weighted at maximum buoyancy.

b. using two weight belt buckles or other methods of reducing risk of

accidental loss of weight.

c. some divers use heavy backplates and/or thread weight onto their

upper harness – this may eliminate the need for a weight system

entirely.

6. The minimum buoyancy you need for a technical dive is sufficient buoyancy

to float your head comfortably above the surface while wearing the entire

kit you need for the dive, including all cylinders, full.

7. Choose your BCD lift capacity with this in mind. Check its buoyancy in

water shallow enough in which to stand. You use double BCDs one at a time

– they don’t double your lift.

8. Buoyancy control underwater

a. With a wet suit, you add and release air from your BCD to control

your buoyancy, just as you do recreational diving.

b. With a dry suit, a heavier rig may require too much buoyancy to off-

set with suit inflation. In that case, you use both your BCD and

inflate your dry suit. This differs from the recreational diving prac-

tice of dry suit only underwater. You inflate your dry suit just enough

to offset squeeze.

c. During descents hold your BCD inflator over your dry suit inflator

so you can inflate both one-handed.

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d. During ascents, set the dry suit dump valve to release expanding gas

automatically. Raise the shoulder with the valve, while dumping gas

from your BCD manually.

e. With redundant BCDs, you do not use the back up unless your pri-

mary BCD fails. Inflating both simultaneously can cause the entire

BCD system to fail. If your primary fails, switch to the backup, and

use it just as you would the primary as you end the dive.

C. Descent checks

1. Technical divers check each other again after entering the water. Depending

on the dive, this may be just under the surface or by pausing in the 5

metres/15 foot to 6 metre/20 foot range, or at the depth where you stage

your first deco cylinder.

2. The team uses the descent check to look for gas leaks (bubble check), con-

firm gear operation and double check rigging.

3. You’ll learn the details of descent checks and practice them later in this

course.

D. Team Diving Gas Handling Considerations

1. Dive team members usually plan to dive using the same gases throughout

the dive, for several reasons:

a. In a gas supply emergency, team mates can use each other’s without

compromising the deco schedule.

b. It reduces confusion about what gas a team mate should be breathing

at a given depth.

c. It allows team mates to share deco schedule in case of lost tables/

computer failure, etc.

d. It keeps the team together, because all will have similar limits and

decompression stop schedules.

2. On a technical dive, all cylinders (singles, doubles, stage bottles, decom-

pression bottles, etc.) require the four following markings:

a. Color coding/marks to identify gas as appropriate in local dive com-

munity or according to local regulations. Include:

• Enriched air nitrox normally has a wide green band with yel-

low borders, and is labeled “nitrox” or “enriched air nitrox,”

or other markings as required by local law/regulations.

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• Oxygen normally is all white or all green with large label

“oxygen”.

• Trimix (oxygen, helium & nitrogen) is varied – commonly

black, blue and green.

• Argon for dry suits usually has a large “ARGON – DO

NOT BREATHE” label.

b. The analyzed content is large enough and placed so team mates

can read it easily while worn (5 - 8 cm/ 2 - 3 in characters is typi-

cal size). For example: “EANx60” or “100% OXYGEN”

c. Near the content, the maximum depth the gas can be breathed safe-

ly (based on PO2 1.4 ata for cylinders used on “working” part of

dive and 1.6 ata for cylinders used only for decompression/safety

stops), is large enough and placed so team mates can read it easily

while worn(5 - 8 cm/ 2 - 3 in characters is typical size).

For Example: “6 METRES” or “50 FEET”

d. The diver’s name.

3. As you learned during the PADI Enriched Air Diver course, cylinder

markings are important for your safety so you don’t breathe the wrong gas

by accident. In technical diving, cylinder markings are important for safe-

ty, because they:

a. identify whose cylinder is whose so you dive the cylinders you

checked.

b. clearly identify what is in each cylinder and the maximum depth

you can breathe from it, reducing oxygen toxicity or decompres-

sion sickness risk.

c. make it possible for team mates to easily check what each other is

breathing.

d. reduce confusion during task loading by being easy to read, even

at a distance.

e. are an additional check/confirmation of cylinder contents.

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4. Additional markings may include

a. Fill date

b. Blender’s name and analysis

c. In areas where recreational divers might recover “lost” cylinders, a

label reading “Decompression Gas – Do Not Remove” may alert

divers that the cylinders are not abandoned and should be left in

place.

5. Commercially made labels for markings are preferred, but duct tape and a

permanent black marker work in a pinch.

6. All divers must personally check the pressure and analyze the contents of

every cylinder they will use. There are no exceptions.

a. In tec diving, you analyze the gas right before the dive as you set

up, even if you’ve analyzed it earlier.

E. Decompression stops

[Note to student: The following sections include decompression stop related dis-

cussions. It’s important to understand the concepts involved, although some of

what you learn will apply primarily after you move to the Tec 45 level and

beyond. Also, they may apply to other divers you’re with.]

1. The most important skill when it comes to making decompression stops is

precise buoyancy control and the ability to maintain depth for extended

periods. This is important because:

a. decompression stops are more critical than safety stops – signifi-

cant variation can affect the quality of decompression.

b. descending while breathing a high oxygen gas can raise the PO2

above 1.6, risking oxygen toxicity and drowning.

c. Although you can often use a line or the bottom to help maintain

stop depth, you’ll practice making stops using primarily buoyancy

control.

2. When decompressing, keep the stop depth at about mid-chest level. The

ideal deco position is horizontal in the water as if swimming (not always

possible, nor essential, but this position theoretically maximizes the avail-

able lung surface area for gas exchange).

3. Your deco software or dive computer dictates the maximum ascent rate.

Note that on decompression dives using air/enriched air, the most common

rate is 10 m/30 ft per minute.

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4. Pay close attention to decompression technique as you practice and

learn. Although not typical at the Tec 40 level, as you move to the Tec

45 level and beyond, decompression can be two or three times longer

than your time on the bottom.

F. Donning and removing stage/deco cylinders

1. Normally you put on your main cylinder(s) and other gear and enter the

water, then put on stage or deco cylinders in the water. If you stage

(remove and place somewhere for later retrieval) your stage/deco cylin-

ders, you remove them underwater on the way out, then replace them

underwater when you return to them.

a. It is not always possible to put on your stage or deco cylinders

in the water; you may have to don them before entering the

water.

[Note to student: At the Tec 40 level, you will usually wear your decompres-

sion cylinder the entire time, though you may don and remove it in the water

before and after the dive. You may also need to remove it underwater to pass

to a team mate in a gas sharing emergency. Although you don’t use multiple

deco cylinders as a Tec 40 diver, in a gas sharing emergency you may end up

wearing a second deco cylinder passed to you by a teammate.]

2. Follow these steps for donning a cylinder.

a. Confirm all hoses are still secured by bands to avoid entangle-

ment.

b. Hold the bottom clip with your left hand and clip it to the left

hip D-ring. (When you wear only one stage/deco cylinder as at

the Tec 40 and Tec 45 levels, it is typically on the left.).

c. Swing the bottle up and secure the upper clip to the chest

D-ring. (A few divers choose to reverse this sequence).

d. Confirm that the cylinder hasn’t trapped any gear you need to

access.

e. Confirm that the valve is closed, though the regulator may be

pressurized.

3. For multiple cylinders

a. A second cylinder may go on the right, though if scootering (not

part of the Tec Diver course), it is common to wear all stage/

deco cylinders on the left. Some divers prefer to wear them all

on the left (aluminum) regardless.

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b. If wearing a second cylinder on the right, be sure the long hose

ends up outside the clips and D-rings so the cylinder does not trap

it.

c. When stacking cylinders (a second chest/shoulder D-ring on the

same side may help)

• The cylinder you will stage (leave) first or use first (while

worn) goes on top.

• The cylinder you’re breathing from goes on top.

d. If carrying right and left, always put the same cylinders in the

same place. The tec community standard is to wear the higher oxy-

gen cylinder on the right (right – rich, left – lean).

4. Removing a stage/deco cylinder

a. You typically do this before exiting the water onto a boat, or when

staging a cylinder at the beginning of a dive for later retrieval and

use.

b. Confirm that the valve is closed and that all hoses are tucked and

secure. The valve must be closed to assure no gas loss while the

cylinder is unattended.

c. Unclip the cylinder from the upper chest D-ring. (Some divers pre-

fer to release the hip D-ring first.)

d. Hold the cylinder by the strap/lower clip and release it from the

hip D-ring.

e. If staging (leaving cylinders on the bottom), the entire team stages

together. Place the cylinder where it will not roll or slide, etc., with

the second stage up and out of the mud/sand. Reconfirm that the

valve is closed and the hoses are pressurized before leaving it, and

reconfirm that you’re leaving the cylinder you intend to. You and

your team mates check each other’s cylinder labels.

f. Stage in order, so that when you switch gases, the cylinder you

need is on top (if you stack them).

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5. Staging and retrieving on the fly (while swimming)

a. After you’re comfortable removing and replacing a cylinder station-

ary, you learn to do so while swimming. This saves time, and may

also be important in a gas sharing emergency situation.

b. Begin by removing the cylinder while swimming as you approach

the stage point. Stop and stage it quickly, remembering you’ll need

to reduce your buoyancy slightly when you let it go.

c. When retrieving cylinder, pick it up and continue swimming (if it’s

not your stop depth) as you put the cylinder on.

d. When ascending to a deco stop, if you’re close to your bottom time

and your first stop is shallower than where you staged your deco cyl-

inder, don’t waste time donning it at the staged depth. Simply grab it,

clip the upper clip to your chest D-ring and continue. Don it com-

pletely after reaching your decompression stop depth.

e. You’ll start learning to do this on Tec 40 Training Dive Two.

G. Gas switches underwater

1. Switching from one gas blend to another is the primary tool for efficient

decompression.

2. However, one of the most common preventable causes of technical diver

deaths is switching to the wrong gas (too high oxygen) for the depth. As a

result, the diver convulses and drowns.

3. To prevent this, apply the following guidelines (not all are possible on all

dives, but all dives allow you to apply some of these):

a. The most effective guideline: When feasible, never take a cylinder

deeper than you can safely breathe it.

• But, for deco, you must be certain that your return/ascent will

return you to where you can retrieve it.

• Do not leave cylinders if getting disoriented and being unable

to find them, or having them swept into current, etc. are

realistic possibilities – open ocean, wreck dives, etc.

• However, this is very feasible at many sites, such as small,

controlled deep sites like springs, quarries, etc. This is also

the procedure used for decompression cave dives.

• Sometimes it’s feasible to run a line from your staged cylin-

ders to where you’re diving.

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b. Personally analyze your gas, and mark your cylinders.

c. Block the regulator mouthpiece on cylinders that you can not

breathe from safely, so that you must remove the block before use.

d. Always follow the complete gas switch procedure (discussed

shortly), step by step, without cutting corners.

e. Never get complacent about staging and gas switches – pay close

attention to what you’re doing.

4. If switching to a staged cylinder, you usually replace it before switching to

it.

5. Remember NO TOX so that you don’t miss any of the steps of a proper

gas switch. You apply this even when switching to a single decompression

cylinder that you’ve been wearing the entire dive.

a. N -- Note your name and the maximum depth on the cylinder

labels (if picking up a staged cylinder, you may do this as you

retrieve the cylinder).

b. O – Observe the actual depth and compare it to the maximum

depth on the label.

c. T - Turn open the valve. Check the cylinder pressure.

d. O - Orient the second stage by pulling it from the retaining bands,

and tracing the hose from the first stage to the second so there’s no

doubt you have the right one. Unblock the mouthpiece (if using a

block), test purge the regulator and then switch to the new gas.

e.

6. When switching from back gas, clip your long hose second stage to your

right chest D-ring. This keeps it from unwinding and getting tangled, and

assures you know where it is. Note that the clip should be breakaway

mounted for hand off without unclipping in an emergency.

7. If switching from another stage cylinder (emergency situation as a Tec 40

diver):

a. Switch to back gas momentarily, close the first cylinder valve and

retuck the second stage hose into bands before going to the next

cylinder. Go through NO TOX at every switch.

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b. For stacked cylinders, you breathe from the cylinder on top.

If switching to the cylinder underneath, secure the first cyl-

inder, unclip it, and then hook it to your hip D-ring by the

top clip. The cylinder dangles out of the way along your

leg.

c. Retrieving cylinders staged correctly places the gas you’re

breathing on top.

VI. Emergency ProceduresManual Supported Content

Study assignment: Tec Deep Diver Manual, pgs 60-64, Emergency

Procedures I, Tec Exercise 1.6, pgs 123-129, Emergency Procedures II,

Tec Exercise 2.6

Learning Objectives


1. What are the emergency procedures for using the long hose second stage to

handle an out of gas emergency?

2. What are the emergency procedures for a massive regulator free flow at depth?

3. What are the emergency procedures for a damaged doubles manifold at depth?

4. What are “S-drills,” and when do you do them?

5. What are the emergency procedures if your BCD fails?

6. What should you do if you experience symptoms of CNS oxygen toxicity?

7. What should you do if you see a team mate breathing an unsafe (too high oxy-

gen) gas for the depth?

8. What should do if your team mate convulses underwater?

9. What should do if you experience difficulty maintaining your depth?

10. What is the general procedure to follow if you’re unable to return to your

planned ascent line?

11. How do you deploy your lift bag or DSMB and reel for use as an emergency

decompression line?

12. What do you do in an emergency decompression situation if your lift bag or

DSMB fails?

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A. Technical diving requires mastering many emergency procedures.

1. These are similar to, but not always identical to, recreational meth-

ods.

2. Technical diving emergency procedures arise from the fact that

ascending directly to the surface is usually not an option.

3. You’ll begin learning these skills in the first training dive and mas-

ter them during subsequent dives.

B. No gas emergency – long hose gas sharing

1. Possible common causes: Poor gas planning, failure to execute gas

management plan, runaway free flow regulator, valve/manifold

failure, unplanned delay in ending a dive.

2. In a no-gas emergency, the most immediate option is to share gas

with the long hose.

a. The receiver signals out of gas.

b. The donor passes the regulator from the mouth to receiver,

unlooping the hose from around the neck in doing so, and

switches to the secondary around the neck. Note: If wear-

ing a snorkel, you must reach high and out to the left to

clear it as the hose unwinds. This is one reason snorkels are

commonly not worn at the Tec 45 level and beyond.

c. The team aborts the dive, staying together, usually side by

side. The long hose gives maximum versatility to handle

the specifics of the situation. Note: If using a Tec 40 rig

with a pony bottle, the gas supply is limited, so it is impor-

tant to begin the ascent immediately to reach a depth at

which the donor can switch to the decompression cylinder.

d. If still in a no-deco situation, the team ascends to the sur-

face. Otherwise, the team ascends with the receiver using

the long hose until reaching a depth shallow enough to

begin breathing from a decompression cylinder.

C. Regulator free flow, gas shut down.

1. As you recall, modern regulators usually free flow if they fail. The

most common cause is poor maintenance. A dislodged first stage

can also cause a runaway gas leak. The most common cause is

impact. In cold water it may be caused by freezing.

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2. Regardless of cause, breathe from the unaffected regulator, then reach back

and close the valve to the free flowing one. (In sidemount configuration, it

will be in front of you, of course.)

3. Abort the dive.

4. Practice this until you can do it independently. (It may help to loosen you

waist band and/or release a crotch strap and lift the cylinder(s) with one

hand while closing the valve with the other.

5. One reason for diving with your valves all the way open (not closed a par-

tial turn) is so they only turn one way – closed.

6. Team mates may assist each other. You’ll practice assisting each other.

This is one reason all divers wear the same basic kit – you don’t have to

figure out which regulator is which.

D. Cylinder isolation

[Note to student: If you’re using doubles for your Tec 40 training, your instructor

may have you practice this skill. If not, you will learn it in your training as a Tec

45 diver.]

1. If you’re wearing doubles and the manifold fails, you have a leak that you

cannot shut down. Common possible causes: Severe impact, improper

assembly, overfilling, poor maintenance.

2. Reach back and close the isolator valve in the center of the manifold. This

will conserve half your remaining gas (in the unaffected side). Abort the

dive.

3. This is similar to closing one of your regulator valves. As with the other

valves, keep the isolator valve all the way open so it only closes one way –

closed – in an emergency.

4. Try to determine which side has the leak. Lean back and see which side the

bubbles are coming from. With the isolator closed, look at SPG – if it’s

dropping rapidly, the leak is on the left. If not, it’s on the right. Breathe

from the regulator on the leaking side until the gas is gone, then switch.

5. Single cylinders do not have any isolator mechanism.

6. If you have an unidentified gas leak behind your head while wearing dou-

bles that you cannot immediately solve, close the isolator immediately

until you sort out the problem. If it is not a failed manifold, reopen the iso-

lator after correcting the problem.

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7. Your team mate may assist, of course. You’ll practice closing the isolator

independently and assisting each other.

E. S-drills

1. Technical divers periodically practice “S-drills” to stay prepared for emer-

gencies. (“S” for safety, or “signal,” “share” and “swim” when sharing

gas).

2. An “S-drill” is a safety drill during which you and your team mates prac-

tice gas sharing with a long hose while swimming, valve shut downs and

in other emergency procedures.

3. S-drills generally take place in shallow water before starting a dive,

though you may practice them during safety stops if they won’t cause

depth control problems. Another option is to make a separate shallow

dive.

4. You perform an S-drill when:

a. Diving with new team mates for the first time.

b. You want to practice and refresh your skills.

c. Your team needs to modify any emergency procedures to address

specific dive requirements.

d. You and your team mates need to confirm that you’re following

the same procedures.

F. BCD failure – how you handle it depends on how you’re equipped, but you

should be always be able to switch to your back up BCD and/or use your dry suit.

You may also be able to:

1. use an ascent line or sloping bottom to control your depth.

2. drop weights and/or no-longer needed stage/deco cylinders, or other

equipment.

3. continue to use the BCD (but not if you’ve switched to your back up

BCD) – most will hold a good bit of air even with a leaking deflator or

puncture (provided it’s not at the top of the bladder). Disconnect a leaking

inflator and orally inflate the BCD.

4. Again, the most reliable overall option is to have a backup (double blad-

der) BCD.

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[! icon]

G. Oxygen toxicity

1. If you experience CNS symptoms (remember VENTID), immediately

switch to your back gas (lowest oxygen). If using back gas, immediately

ascend.

2. Check your depth and reconfirm the gas you’re breathing (you may have

unknowingly descended below the maximum depth for the blend).

3. Breath back gas for 15 minutes after all CNS symptoms subside before

returning to higher oxygen gas at its maximum depth. If possible, do not

switch back until shallower than maximum depth, such as when using high

oxygen gas for conservatism. Do not count the time on back gas as decom-

pression time if you’re on an accelerated decompression schedule (Tec 45

and above). On no stop dives, stay on back gas, ascend immediately and

abort the dive (again, the inherent risk reduction advantage of staying with-

in the no stop envelope).

4. When in doubt, ascend and get your PO2 below 1.3 ata/bar, or lower if fea-

sible. (Many EANx computers display your PO2). Better to increase your

risk of DCS (which is usually treatable) than to have a substantial risk of

convulsing and drowning (which is usually fatal). If you must skip stops to

ascend, extending the shallower stops may reduce your DCS risk.

H. Team mate breathing wrong gas

1. If you note a team mate breathing gas while deeper than its maximum (like

during the X step of NO TOX), immediately pull the second stage from

your team mate’s mouth and provide your long hose.

2. This may seem extreme, but oxygen convulsions can come quickly, sud-

denly and without warning – seconds count. The higher the oxygen partial

pressure above 1.6, the faster they can occur. Don’t waste time trying to

signal – your team mate will know exactly what happened if you do this.

3. Your team mate stays on back gas (own or yours) until sorting out the

problem and finding the correct cylinder.

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4. Again, following NO TOX avoids this problem.

[! icon]

I. Team mate convulses underwater

1. If a team mate convulses underwater, the concern is drowning. If possible,

hold the second stage in the diver’s mouth to minimize the risk of drown-

ing. As you recall from the PADI Enriched Air Diver course, the priority

is getting the diver to the surface. (Note that a full face mask greatly

reduces drowning risk in the event of an underwater convulsion.)

2. If team mate begins to sink, switch to back gas before assisting so you

don’t risk CNS oxygen toxicity if you must descend in the process.

3. How you best help your team mate has many variables depending on your

decompression status – you may risk getting bent if you take the victim to

the surface yourself. You’ll have to quickly consider these options:

a. If you have support divers at your decompression stops, they can

take your team mate to the surface – this is the best option.

b. It’s worth noting that when taking a convulsing diver to the surface

(you or the support divers), the general recommendation is if the

regulator is in the victim’s mouth, to hold it in place and wait for

the convulsion to cease, then bring the victim up, maintaining a

neutral head position that allows air to escape from the airway.

c. It’s generally recommended that rescuers don’t drop the victim’s

weights before reaching the surface, because they may lose control

of the victim and put themselves at risk.

d. If you’re decompressing with high oxygen EANx or pure oxygen

for conservatism with a single gas table or computer, your risk of

getting DCS may be minimal even with deco time remaining. The

higher the oxygen above what the table/computer thinks you’re

using, and the longer you’ve deco’d, the less the risk.

e. If risk is high, and you have a long deco ahead and have not start-

ed, and there’s assistance at surface, you may just need to let the

victim surface for topside personnel help. If there’s no help at the

surface, this may still be the best you can do.

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f. If risk is moderate, you may choose to risk getting DCS,

which is usually treatable, in exchange for a chance to save

or restore your team mate’s life. This is your decision – and

it’s not always an easy one.

4. Note that without support divers, or at least surface support, han-

dling this becomes more complicated as decompression gets lon-

ger. Consider planning your dives so that your team never exceeds

1.4, even during deco.

J. Difficulty maintaining depth

1. You may have trouble maintaining depth due to sudden BCD fail-

ure, down/up currents, unexpected weight (if someone were to

hand you something, for example), etc.

2. If possible, immediately grab a line to steady your depth.

3. If descending, switch to back gas to avoid oxygen toxicity.

4. If you have a runaway BCD inflator, disconnect it and switch to

your back up BCD, use dry suit, get team mates to give you weight

(used stage/deco cylinders), etc. to stabilize depth control.

5. If in decompression, do not count “sink” time as stop time. If you

momentarily (less than a minute) ascend above decompression

depth and quickly return, resume decompression and add a minute

to the stop. As a precaution, it’s a good idea extend your last stop

five to ten minutes (safety stop within a decompression stop). A

dive computer will adjust deco time for time below stop depth.

6. Remember that it’s critical to maintain depth while decompressing

– do not take this problem lightly.

K. Unable to return to ascent line

1. If unable to return to planned ascent line (lost, current, insufficient

gas), team stays together, retrieves any staged deco cylinders and

deploys lift bag or DSMB and reel.

a. The team ascends on lift bag/DSMB line and completes

decompression adrift.

b. The dive boat follows the lift bag and picks up divers at the

end of deco.

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c. In environments where this can happen, dive planning includes

making sure the boat is prepared for this contingency, and that dive

teams will have deco gas without returning to the planned ascent

line.

d. Note that because a boat may have to leave its mooring or anchor

line for any number of reasons, in tec diving it is seldom appropri-

ate to stage deco tanks by hanging them on lines under the boat.

2. To deploy lift bag/DSMB (you’ll practice this several times):

a. Retrieve the bag/DSMB and reel. Put a puff of air in it so it floats

a bit for easy handling and secure the reel line to the bag clip with

a double loop.

b. If it is an open bottomed DSMB or a lift bag, hold the reel in your

extended right hand, apply tension from a finger on the spool, in

sight with a tight line to the bag in your left hand; bring the

DSMB/bag to your mouth and inflate as full as possible by “puff-

ing” from the second stage in your mouth. This technique keeps

the line under control and in sight, and away from your gear so it

doesn’t tangle.

c. If it is a closed DSMB, hold the reel with the line wound in as far

as possible, maintain tension with a finger (do not lock the reel)

and inflate the DSMB through the oral inflation tube or LP inflator

(as appropriate). Keep the reel and line away from your gear to

avoid entanglement.

d. Hold on to something with your legs, have team mates hold you

down, etc. so you can fill the bag/DSMB as much as possible

without it carrying you upward. The more you fill it, the better.

e. Release the bag and allow it to ascend. With many DSMBs and

bags, you must maintain continuous tension as it rises and during

your ascent or the bag will spill and sink at the surface. Some

models have one- way valves that prevent this, but you should still

maintain tension to keep the bag/DSMB under control.

f. After it reaches surface, pull in the line and take up slack to make

as vertical as possible. Your bubbles tend to push it, so don’t

expect it to maintain your depth – you have to do that with buoy-

ancy control.

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3. If your lift bag or DSMB fails

a. Use a team mate’s – if the environment calls for having a lift bag/

DSMB, every diver should have a lift bag/DSMB and reel.

b. If your bag/DSMB went up but doesn’t have enough buoyancy, you

can clip a team mate’s to your line with a carabineer or large bolt snap

and send it up. This combines their buoyancy and eliminates the need

for a second line.

c. If your team mate’s bag/DSMB is unavailable (due to team separation

or loss), reel in your bag and try again – it may have simply spilled.

d. If that doesn’t work, ascend and deco midwater by hovering and

watching your depth closely. Upon surfacing, deploy a inflatable sig-

nal tube, and signal the boat.

Tec 40 Knowledge Development TwoI. Thinking Like a Technical Diver Manual Supported Content

Study assignment: Tec Deep Diver Manual, pgs 64-64, Thinking

Like a Technical Diver I, Tec Exercise 1.7

Learning Objectives


1. What does Hick’s Law tell us about reaction times in an emergency?

2. What is the KISS principle, and how does it relate to technical diving?

3. Why does “cutting corners” lead to technical diving accidents?

A. Becoming a technical diver includes learning to think like one. In

this section, you begin learning principles that will influence how

you plan, execute and learn from every dive you make.

B. Establishing emergency procedures – is it better to have many ways to handle an

emergency, or just one or two?

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1. Hick’s Law (1952) states RT = K log2 (N + 1), where RT = reaction time, K

= a constant and N = the number of possible choices.

a. Hick’s Law explains how people make decisions among multiple

choices in different types of situations

2. Without going into the details, with respect to situations such as tec diving

emergencies, Hick’s Law states that the more ways you have to respond to

an emergency, the longer it takes to react, with the response time increasing

substantially for each added choice.

3. Therefore you want the fewest procedure choices possible – only as many as

you need to cover all reasonably likely contingencies.

4. Aviation, spaceflight, anesthesia, emergency medicine and the nuclear

power industry, among others, have all proven this; they have found the

most effective emergency responses arise from relatively few, standardized

and practiced procedures.

C. KISS principle – Keep It Super Simple.

1. The KISS principle says that the simplest way to accomplish anything is

usually the best way.

2. Technical diving creates high mental and physical demands; complex tasks

to accomplish particular missions have a high likelihood of failure.

3. Eliminate complexities and simplify:

a. Break complex tasks into several simple tasks to handle over two or

three dives.

b. Break complex tasks into simple tasks, each handled by a different

diver or dive team.

c. Question the complex – does it really have to be that difficult?

d. Accept the complex to make things simple; e.g., a double bladder

BCD is more complex than a single bladder, but tremendously sim-

plifies handling primary BCD failure.

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D. The Mission

1. No matter what you plan to accomplish on a technical dive, every technical

dive has one overriding mission that you never compromise: To return with

all your team mates unharmed.

2. Never compromise safety.

a. As you learned, compared to recreational diving, technical diving acci-

dents arise from relatively short error chains.

b. Therefore, you cannot cut corners in equipment preparation, planning

or executing your dive. Doing so greatly increases the chances of an

accident.

c. E.g. In recreational diving, despite recommendations otherwise, a

diver might computer dive even after forgetting to bring back up tables

and gauges. The risk is not that high because if the computer fails, the

recreational diver is within no decompression limits and simply sur-

faces.

d. A technical diver who dives without back-up tables and gauges could

end up paralyzed for life, because computer failure would leave no

means for determining the required decompression.

e. The most common preventable cause of tec diving accidents is cutting

corners. It’s easy to rationalize “just this once,” but “just once” is the

number of failures required, without a contingency, to get hurt or

killed.

f. Technical divers follow all safety guidelines to the best of their abili-

ties every time. They never compromise safety for convenience, cost

or peer pressure, even if it means missing what would otherwise be a

great dive.

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II. Gas and Decompression PlanningManual Supported Content

Study assignment: Tec Deep Diver Manual, pgs 88-93 Introduction to

Decompression Stop and Gas Switch, Extended No Stop Diving, Equivalent Air

Depths (Continued) and Equivalent Narcotic Depths, Ideal Enriched Air for a

Particular Depth, Determining Gas Supply and Reserve Requirements for

Multiple Depths and Decompression stops (first page only); pgs 97-99 Desk Top

Decompression Software Tec Exercise 2.2, Questions 1-8 & 10. Pg 157 down to

“Example” on pg 158, Planning a Decompression Dive Using a Single Gas

Computer.

Learning Objectives


1. How do you determine required decompression stops using a single gas computer or

tables?

2. How do you use switches to enriched air or oxygen to make decompression stops or

safety stops more conservative when using a single gas computer or single gas tables?

3. What is accelerated decompression?

4. What is a gas-switch, extended no stop dive?

5. What is your EAD when breathing pure oxygen?

6. What is an END, and what are the two different assumptions based on it?

7. Why do you assume your END does not change when using enriched air as compared

to normal air?

8. How do you normally determine the “ideal” enriched air for a particular depth?

9. How do you determine your gas requirements for the deepest portion of your dive?

10. What is “desk top decompression software,” and what are the risks and benefits of

using it?

11. What are six advantages of decompressing based on a single gas computer or tables

and using enriched air and/or oxygen for conservatism?

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A. Introduction to decompression stop and gas switch, extended no stop diving.

1. As you recall on a decompression dive, you make decompression stops

to allow excess nitrogen (or other inert gas) to dissolve out of your

body tissues. Failure to make these stops risks decompression sickness.

2. Single gas (air or enriched air) dive computers suitable for technical

diving automatically show you the decompression requirements during

the dive (check the manufacturer literature for specifics).

a. This is the simplest form of planning a decompression dive.

b. This is the type of decompression diving you will be qualified

for as a Tec 40 diver.

3. Common published dive tables, such as the US Navy Standard Air

Tables or Canada’s DCIEM air tables, specify the depths and durations

for stops for a given depth and time dive. These are not commonly

used in technical diving, however.

4. You will be using desk top decompression software to generate tables

for dive planning and/or backup purposes with your dive computer

(more about this shortly and in Tec 40 Practical Application Two).

5. For the maximum reliability, you want to plan your dives using gener-

ated tables and dive computers based on decompression models that

are within the limits of established test data. Practically speaking, this

means:

a. use widely used, accepted decompression models (virtually all

commercially available software and dive computers employ

such models)

b. stay well within table/dive computer limits

6. Single gas computers assume you decompress using the same gas you

breathed on the bottom. You can set decompression software to do the

same.

a. Switching to EANx with more oxygen than the gas you used on

the bottom, or to pure oxygen, allows nitrogen to defuse from

your body more rapidly.

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b. Switching to EANx/oxygen (after ascending shallow enough to

avoid oxygen toxicity with the new gas), but decompressing

according to your single gas computer/table, yields the most con-

servative decompression. This is one of the most common and eas-

iest ways to execute a decompression dive (more about this short-

ly).

c. On a no stop dive, you can switch to EANx/oxygen during a safety

stop to make it extra conservative.

Example: You dive to 40 metres/130 feet using EANx24 with an enriched air

computer. Upon ascent, your computer shows you have stops at 6 m/20 ft and 3

m/10 ft. You ascend to 6 m/20 ft and switch to EANx50 and finish decompression

according to your computer.

7. Because switching to higher oxygen EANx and/or pure oxygen speeds

nitrogen release, gas switches can also be used to shorten your required

stop times by using special multiple gas computers or custom dive tables.

a. This is called accelerated decompression. This is less conservative,

but gets you out of the water sooner. You qualify to use accelerated

decompression at the Tec 45 level.

b. By using multiple gas computers/custom dive tables, you can make

gas-switch, extended no stop dives. You switch to higher oxygen

EANx as you ascend to maximize your no decompression dive

time, making very long no stop dives possible. You also qualify to

make gas switch, extended no stop dives at the Tec 45 level.

• Switching gases to extend your no stop time is a very use-

ful, but sometimes overlooked, technique.

• Avoiding the need for decompression stops keeps your

logistics simpler, expands your options and makes it easier

to deal with many types of emergencies.

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B. Equivalent Air Depths (continued) and Intro to Equivalent Narcotic Depths

(ENDs)

1. According to the EAD formula, your EAD when using pure oxygen

(something you qualify to do at the Tec 45 level) is always -10

metres/-33 feet because the PN2 is 0, lower than air at the surface (even

at altitude). The mathematical result is a constant negative depth.

a. Your EAD with any EANx is less than your actual depth. The

more oxygen, the greater the difference.

b. The reason EANx/oxygen speeds nitrogen elimination is that

there is a greater difference between the pressure of the nitrogen

dissolved in your body and the nitrogen in the gas you’re breath-

ing.

2. However, it is your actual depth that matters with respect to bubble for-

mation at a decompression stop.

a. Your decompression stop depth should never be shallower than is

indicated on your computer or backup dive table.

b. It can be deeper; your computer will make your decompression

longer, however.

c. When decompressing on pure oxygen (as a Tec 45 diver), it can

be deeper without affecting your decompression time (but you

can’t be deeper than 6 m/20 ft, where the PO2 = 1.6).

3. Equivalent Narcotic Depth (END) calculates the expected narcosis for a

gas mix, compared to an equivalent depth as if breathing air.

a. At one time, END was sometimes calculated based on the

assumption that oxygen is not narcotic.

b. Today, the thinking is that oxygen is as narcotic as nitrogen.

Therefore, you assume your END doesn’t change when using

EANx.

c. ENDs are commonly used, however, with helium mixes, because

helium is not narcotic. You will learn more about using ENDs as

a Tec Trimix 65 diver and a Tec Trimix Diver.

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C. “Ideal” EANx for a particular depth

1. The “ideal” gas is the one that gives the most no stop time/ least deco time

within oxygen exposure limits.

2. For the vast majority of dives, this is the EANx with its 1.4 maximum

depth that is equal to, or just exceeds the dive depth.

3. Use the Maximum Depth Table in the Appendix of the Tec Deep Diver

Manual to find the appropriate blend.

Example: What is the “ideal” EANx for a dive to 40 metres/130 feet?

Answer: EANx28. In the 1.4 column find 40 (metric) or 132 (imperial)

opposite 28%, indicating enriched air with 28 percent oxygen.

D. Gas requirements for the deepest portion of your dive

1. To determine the gas you need for a given depth, you multiply your SAC

(Surface Air Consumption) rate by the number of minutes at that depth and

by the conversion factor for that depth. Use the SAC Conversion Factors

tables in the Appendix of the Tec Deep Diver Manual (round up to the next

greater depth if the exact depth isn’t on the table).

2. The formula is

gas required = SAC X min X conversion factor

3. Note: The conversion factor is simply the absolute pressure in

atmospheres:

Metric: (D in metres + 10) / 10 Imperial: (D in feet + 33) / 33

4. Example, metric

If your SAC is 24 l/min, how much gas would you consume in 15 minutes

at 30 metres?

Answer: 24l/min X 15 min X 4.0 = 1440 litres

Example, imperial

If your SAC is .7 cf/min, how much gas would you consume in 15 minutes

at 100 feet?

Answer: .7 cf/min X 15 min X 4.0 = 42 cubic feet

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E. Desk top decompression software

1. The standard practice in technical diving is to plan dives using desk top

decompression software (“deco software” or “deco program” for short).

These are personal computer programs that calculate your gas require-

ments as part of generating custom decompression tables.

a. Although called “desk top,” deco software is available for PDAs,

iPhones and other portable devices, as well as for personal comput-

ers.

b. Some desk top decompression software links to special dive com-

puters that calculate your dive within a calculated range. This com-

bines advantages of deco software with dive computer.

2. Benefits of using deco software include:

a. Generates dive tables (for planning and for dive computer back up)

for exact time/depth range and gas blends you’ll be using, as well

as for contingency situations (exceeding planned time or depth).

b. Calculates gas supply requirements based on your SAC rates.

c. Calculates oxygen exposure (OTU, CNS clock and PO2).

d. Reduces potential for human error in several aspects of dive plan.

e. Most programs allow you to alter the decompression model to be

more or less conservative based on numerous factors (personal

physiology, water temperature, etc.)

f. Makes it feasible to quickly compare the variables of several possi-

ble dive profiles; by hand this takes hours.

3. Using any decompression software, dive computer or dive table carries

risks that you must accept. Because people vary in their physiology, no

software, dive computer or table can guarantee that DCS or oxygen toxici-

ty will never occur, even within the limits they provide. Extremely long

dives, dives involving gases other than oxygen and nitrogen, and dives

with reverse profiles carry the further risks of being somewhat experimen-

tal because they may take you outside the body of well established test

data.

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Learning Objectives


1. What is a “bounce” dive?

2. Why is it recommended that you switch to a higher oxygen EANx for decompression

without accelerating your decompression, and/or set your dive computer for an EANx

with less gas than actual, if making a “bounce” technical dive?

E. “Bounce” dives

1. A short dive to any depth is called a “bounce” dive.

a. The definition is imprecise – what one person calls a bounce dive

another may not.

b. It is possible to make dives within the scope of Tec 40 qualifica-

tions that some would be consider bounce dives.

2. There are some anecdotal concerns about bounce decompression dives

a. Some people think DCS data indicate that short, deep dives with

short decompression requirements have a higher DCS risk than

would be expected based on decompression models

b. Again, definitions of “short” and “deep” and “risk” are subjective in

this context.

c. The concerns are hypothetical and not quantified, but they exist

nonetheless.

3. To minimize bounce dive concerns (at all levels):

a. Plan your dive with your computer set for air or an EANx with less

oxygen than you actually use.

b. Use a single gas computer, or if

using a multigas computer,

leave it set for your bottom gas,

but decompress with an EANx

blend with more oxygen.

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c. Either of these (or both) will make your decompression more conser-

vative.

• The required decompression time for a short, deep dives is

correspondingly short. Deco is so short there is no meaning-

ful benefit to accelerating decompression. Instead, you use

EANx to make your decompression more conservative

instead of shorter.

It is common to extend the last deco stop two or three minutes as well.

Example: You dive to 40 metres/130 feet. You leave your dive com-

puter set for air, but you actually dive using EANx25 as your bottom

gas. You decompress with EANx40, but you leave your dive comput-

er (if it is a multigas model) set for air during decompression.

d. You will plan your dives as a Tec 40 diver based on decompressing

as if using your bottom gas, but using EANx to make your decom-

pression more conservative.

Exercise, other Delivery Content, Tec 40-41. A “bounce” dive isn’t defined precisely, but means a short dive to any depth.

o True

o False

2. To minimize bounce dive concerns (choose all that apply):

o a. set your dive computer for air or EANx with less oxygen than the gas you actual-

ly use.

o b. accelerate your decompression.

o c. decompress with a gas that has more oxygen than you set your computer for.

o d. ascend rapidly to minimize your time at depth.

How did you do?

1. True. 2. a, c.

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III. Putting it together – Tec 40 Gas and Decompression Planning


Learning Objectives

1. How do you use desk top decompression software to plan a decompression dive based

on a single gas, with no more than 10 minutes of decompression and a maximum depth

of 40 metres/130 feet?

2. How do you use decompression software to determine your gas supply requirements?

3. What is the minimum reserve gas you should have on a technical dive?

4. How do you set your dive computer to follow the plan you made with your decompres-

sion software?

5. How does your team stay together when using dive computers to provide decompres-

sion information?

6. What limits tell you it is time to end your dive?

7. How do you calculate turn pressure?

8. How do you account for your oxygen exposure when using a gas with a higher oxygen

content than you set your dive computer for?

9. What do you do if your desk top decompression software and dive computer differ sig-

nificantly in their decompression information, or if your gas requirement calculations

appear to be off?

A. Starting with Tec 40 Practical Application Two, you’ll begin planning decompres-

sion dives using desk top decompression software.

1. Your dive planning will continue throughout the course and be the basis

for simulated and actual decompression dives you make.

2. The methods you learn also form the foundation for all your subsequent

technical dive planning. However, gas and decompression planning

becomes more complex as you go deeper and have longer decompression.

B. You will follow these basic steps:

[Note: Your instructor will take you through this, step by step, during Tec 40

Practical Application Two, followed by you and your team mates planning a

dive.]

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1. Launch the desk top decompression program (may be iPhone or PDA based

as long as it provides decompression and gas supply calculations, as well as

the ability to choose different gases).

2. Set the dive characteristics and presets.

a. Select metric or imperial, open circuit (not closed circuit rebreather).

b. Working and decompression SAC rates

• You will determine your working (bottom) SAC rate during

Tec 40 Practical Application Two based on the data you gath-

ered during Tec 40 Training Dive One.

• You will gather decompression SAC rate data during Tec 40

Training Dive Two. In the meantime, use 2/3 thirds your

working rate.

• Your program may refer to SAC as RMV.

c. Select the single gas you want to use for decompression calculations

• You will probably use an EANx blend for bottom gas.

• Use the Maximum Depths tables in the Tec Deep Diver

Manual to find the highest oxygen percentage for the EANx

to your planned depth (PO2 1.4)

• Set the program for the EANx blend you will use, or for one

with lower oxygen. At the Tec 40 level, it is simplest to set

for air most of the time (21%).

• You will probably use another EANx with higher oxygen for

decompression. Do not set the program for this gas at this

time.

3. Enter your planned depth and time into the program.

a. Have the computer calculate your decompression. If it is longer than

10 minutes, enter a shorter time, a shallower depth or both.

• Remember, as a Tec 40 diver, your limits are 10 minutes total

decompression time and 40 metres/130 feet maximum depth.

• For simplicity, your dives will be planned as though the

entire dive will be made at the deepest depth. At higher train-

ing levels, however, you will learn to add planned depth

changes.

b. Enter depths/times until the total decompression time required is 10

minutes or less.

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4. Use the program to determine your gas requirements based on your SAC

rates, for the planned dives.

a. Some programs do this each time they calculate decompression.

b. Most programs will show you the gas requirements before and

after calculating your reserve.

c. In technical diving, the standard minimum reserve is 33 percent

(rule of thirds), meaning that one third of all your gas is for emer-

gencies only. That is, the minimum amount of gas you should have

on a dive 1.5 times the amount predicted for the dive and the

decompression, based on your bottom and decompression SAC

rates.

d. If your program doesn’t determine reserve, simply multiply the

predicted gas requirements by 1.5 to get the minimum gas volume

you should have with you on your dive.

• If you need a pony bottle or a decompression cylinder to

meet the required minimum volume, it should be at least

1/3 of your total gas supply.

• Note: At higher tec levels (Tec 45 and up), you will calcu-

late individual gas blends independently and have to have

1.5 times the predicted requirements for each individual

gas. Planning your decompression based on a single gas at

the Tec 40 level simplifies this.

e. If the minimum gas volume is greater than the capacity of the

cylinder(s) you have will available, then plan a shorter/shallower

dive until the gas requirements (including reserve) are within the

available capacity.

f. Because divers have differing SAC rates, each diver on the team

calculates gas requirements for the team’s planned dive.

• The team works together with the program until arriving at

a depth and time that meets the gas supply requirements for

everyone.

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• A common strategy is to plan the dive based on the highest

SAC rates (bottom and deco), with all divers carrying the

predicted amount of gas (including reserve). This is accept-

able, because it simply adds reserve for divers with lower

SAC rates.

g. After you have a final decompression schedule with gas require-

ments that work for the team, print out the decompression schedule

and gas requirements for use at the dive site.

• If using only a single computer, print out backup tables to

laminate (or list them on a slate) and use with a timing

device and depth gauge in the event of computer failure. It

is recommended that you print schedules for your planned

depth and time, as well as plus and minus five minutes and

plus and minus 3 metres/10 feet (nine schedules total).

5. During equipment setup for the dive, set your dive computer(s) for the

EANx blend or air that you used in the decompression software.

a. Your actual EANx blend may have a higher oxygen content, pro-

vided you don’t exceed a PO2 of 1.4 at your deepest depth.

b. Your decompression cylinder may have EANx50 (or a blend with

less oxygen). Do not decompress with it at a depth where the PO2

exceeds 1.6.

c. These gases with higher oxygen content simply make your decom-

pression more conservative.

d. During the dive, you and your team mates may have slightly differ-

ent decompression schedules due to slight variances in your depths,

as well as differences in your dive computer’s decompression mod-

els.

• To stay together, the team stays at each stop until all com-

puters clear all divers to ascend to the next stop or surface.

• If using tables (back up situation), team stays at each stop

until all computers clear all divers to ascend, or for the table

stop time, whichever is longest.

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6. Limits that end the dive.

a. In technical diving, your dive ends when anyone on your dive team

reaches any of the following, whichever comes first:

• you reach the planned bottom time (what you used in the

decompression software)

• your or a team mate’s dive computer shows 10 minutes

decompression time required (or less if the planned decom-

pression was less)

• It is important to turn the dive with the planned

decompression time showing, even if the bottom time is

less than planned and the required decompression is

still less than 10 minutes, because your decompression

gas volume requirement is based on the planned

decompression time.

• you or a team mate reaches turn pressure on your gas supply

7. Turn pressure is the reading on your SPG that indicates it is time to head up.

It is calculated based on the cylinder pressure of the gas volume your soft-

ware predicts you’ll use on the bottom. Knowing your turn pressure and

having it written on a slate assures that you head up with the gas for decom-

pression and reserve intact.

a. Almost all software will tell you the required gas for all individual

gases, but many do not tell you how much you use on the bottom, or

calculate turn pressure.

b. To determine your turn pressure, you may therefore have to do so

with a calculator and the tables in the Tec Deep Diver Manual.

c. You will use turn pressure formulas, as well as what you already

learned about SAC and actual gas supplies in Tec 40 Knowledge

Development One.

• Note: For simplicity, treat your descent as time on the bot-

tom. This gives you a slightly higher reserve.

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d. Formulas:

• Metric: Turn pressure = start pressure – (bottom volume ÷

cylinder capacity)

• Imperial: Turn pressure = starting pressure – (bottom vol-

ume ÷ baseline)

e. Examples

Metric example:Your working SAC rate is 19 litres per minute. You plan a dive to 40

metres for 10 minutes. Your decompression software shows that using an

11 litre cylinder, working pressure 205 bar, and a 9 litre deco cylinder will

provide the gas volume you need. By what pressure should you start your

ascent?

First, find your bottom volume.

Bottom volume = minutes X SAC X conversion factor

Bottom volume = 10 X 19 X 5.2

Bottom volume = 988 litres

Assuming your 11 litre cylinder is full (205 bar), then:

Turn pressure = 205 – (988 ÷ 11)

Turn pressure = 115 bar

To manage your gas appropriately, you should begin ascending when or

before your SPG reaches 115 bar.

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Imperial example.

Your working SAC rate is .8 cf per minute. You plan a dive to 130 feet for

10 minutes. Your decompression software shows that using an 80 cubic

foot cylinder, working pressure 3000 psi, and a 65 cubic foot deco cylin-

der will provide the gas volume you need. By what pressure should you

start your ascent?

First, find your bottom volume.

Bottom volume = minutes X SAC X conversion factor

Bottom volume = 10 X .8 X 4.9

Bottom volume = 39.2 cubic feet

Next, find the baseline for an 80 cubic foot cylinder. Recall that to get the

baseline, you divide the working capacity by the working pressure

Baseline = cap ÷ working pressure

Baseline = 80 ÷ 3000

Baseline = .0267

Assuming your 80 cubic foot cylinder is full (3000 psi), then:

Turn pressure = 3000 – (39.2 ÷ .0257)

Turn pressure = 1474 psi.

To manage your gas appropriately, you should begin ascending when or

before your SPG reaches 1474 psi.

f. Note that in both examples that your deco cylinder is required to

meet the required reserve (rule of thirds).

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C. Oxygen exposure calculations

1. If your dive computer was set for air or EANx with less oxygen

than your actual bottom gas and/or you switched to a higher oxy-

gen decompression gas for conservatism, you have to account for

your oxygen exposure after the dive, because your dive computer

didn’t know how much oxygen you actually had in your

cylinder(s).

2. After the dive, use desktop software and enter the dive as you actu-

ally made it – actual depths, times and gases used. Record your

OTUs and CNS clock for planning subsequent dives.

D. Repetitive dives

1. Plan repetitive dives as you did the first dive, but recall that you

must enter the first dive data and your surface interval so the pro-

gram can account for residual nitrogen.

2. When planning a repetitive dive, enter the actual dive as made.

You may also use the previous dive as planned if it yields a more

conservative repetitive dive plan.

3. If OTUs or CNS could approach their maximums – unlikely within

Tec 40 limits, but possible if you make several repetitive dives –

after planning your dive based on a single gas, enter the planned

depths, times and stops based on the actual gas blends to make sure

you will remain within oxygen limits.

E. Making software line up with your dive computer

1. After a few decompression dives, you may find that your decom-

pression software is more conservative than your dive computer, or

vice versa.

a. Be sure your backup computer and/or your team mate’s

computers are similar to your computer to rule out a prob-

lem with your computer.

2. If you don’t spend the majority of the time at the deepest depth,

your dive computer would be expected to be less conservative than

your software, because it calculates the slower nitrogen absorption.

Don’t make any adjustments on this account.

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3. If you do spend the majority of the time near the deepest depth, there may

be some difference in the required stops and some variation in the total

decompression time due to minor differences in the decompression mod-

els. This is normal.

4. If there is a large difference between your decompression software and

your dive computers (enough to substantially throw off gas supply calcu-

lations etc.), contact the software author and/or the dive computer manu-

facturer. You can adjust safety factors above the default settings to make

software more conservative, but do not make it less conservative unless

advised to do so by the software manufacturer.

5. Assuming no unforeseen emergencies, you should surface from a dive

with your reserve gas supply intact. If you have substantially more or less

gas:

a. First, confirm your working and decompression SAC rates. Adjust

your SAC rates in the software if necessary.

b. If your SAC rates are accurate and you’re coming up with a bit

less gas than you should, it is typically that your software predicts

less decompression than does your computer.

c. Check your decompression software setting and adjust it so it is

more conservative and predicts a bit longer decompression.

d. If the decompression seems to be in line (close match between

your dive computer and the software), it may be how the software

calculates gas use. Increase your SAC rate setting even if that

makes it high compared to your calculations.

e. Do not adjust anything if you have too much gas, unless the sur-

plus is extreme. Too much gas is seldom a problem.

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Exercise, other Delivery Content, Tec 40-51. At the Tec 40 level, the recommendation is that you use EANx for your bottom gas and

set your decompression software dive

o a. for the gas you’re using.

o b. for an EANx blend with more oxygen.

o c. for at least two different gases.

o d. for air or an EANx blend with less oxygen.

2. To determine your gas supply requirements, you must enter your _________ into the

software.

o a. decompression profile

o b. SAC rates

o c. bottom gas

o d. dive computer model

3. The minimum gas reserve you should plan for on a technical dive is ________ of your

total gas supply.

o a. a quarter

o b. a third

o c. half

o d. two thirds

4. At the Tec 40 level, you set your dive computer to follow the plan you made with your

decompression software by setting it for the EANx blend you used for your decompression

planning with the software.

o True

o False

5. When using computers to provide decompression information, the team stays together.

All divers stay at each stop until all computers clear all divers to ascend to the next stop.

o True

o False

6. When you or a team mate reaches any of the following, you should begin your ascent

(choose all that apply):

o a. your planned bottom time

o b. a dive computer shows 10 minutes decompression required

o c. you have a decompression stop at 18 metres/60 feet

o d. turn pressure on your SPG

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7. You calculate turn pressure by determining how much cylinder pressure you would use

for the volume software predicts you will consume on the bottom.

o True

o False

8. To account for your oxygen exposure when using a gas with a higher oxygen content than

you set your dive computer for

o a. you needn’t do anything because the difference is negligible.

o b. you need to dive with a third and fourth dive computer set to the actual content.

o c. you enter the actual dive with the actual gases into your software.

o d. All of the above.

9. If your gas requirement calculations appear to be off, your first step is to confirm your

working and decompression SAC rates.

o True

o False

How did you do?

1. d. 2. b. 3. b. 4. True. 5. True. 6. a, b, d. 7. True. 8. d. 9. True

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IV. Murphy’s Law, reserves and a Good Diver’s Main objective Is To LiveManual Supported Content

Study assignment: Tec Deep Diver Manual, pgs 101-107, Thinking Like a Technical

Diver II, Team Diving II, Tec Exercise 2.3, pgs 109-113, Predive Check, Technical

Diving Hand Signals, Tec Exercise 2.4, questions 1-3 and 9-15.

Learning Objectives


1. What do you assume about every technical dive?

2. What do you take for granted about a technical dive?

3. What question do you ask yourself as you plan each step in a technical dive?

4. What is your most important resource in an emergency, and what provides this resource

in an emergency?

5. What is the principle for your gas reserves and how do you apply it during an open

water deep technical dive?

6. What are the seven primary segments to planning a deep technical dive?

7. What recall phrase can you use to recall the seven segments for planning?

8. What are the substeps for each of the seven segments?

9. What is the predive check recall phrase for technical diving?

10. What steps do you include in a predive check?

11. How, in the field, do you determine the one-third pressure for cylinders?

12. How do you perform a bubble check?

13. How do you perform a descent check?

14. How do you use one hand to signal numbers to a team mate?

15. What do the thumbs-up, fist and “okay” hand signals mean on a tec dive?

A. As a technical diver, you always assume Murphy’s Law: Anything that can go

wrong will go wrong.

1. Assuming failures prompts you to plan for them.

2. Therefore, take nothing for granted on a technical dive.

B. As you plan each step in a dive, ask yourself, “What aspect of this can fail and hurt

or kill me?”

1. For every reasonably possible failure or problem you can imagine, have a

workable solution before beginning the dive.

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2. Within reason, make contingency plans that do not require your team-

mate’s assistance as your first option.

3. Remember that it’s impossible to anticipate all problems – but you can

anticipate the most common and likely.

C. Reserve gas

1. In an emergency or other problem, your most important resource is time.

2. Your gas supply provides time, so it’s your reserve that gives you time to

deal with an emergency – especially important for an unanticipated emer-

gency.

3. As discussed in the previous section, the most common reserve is the rule

of thirds. The principle for using reserves is (if using thirds):

• Use no more than two thirds of supply on the bottom and during

all deco stops that you make with it – determining the pressure at

which you need to start your ascent should be part of your gas

planning.

• As a Tec 45 diver and beyond, you learn to use no more than two

thirds of each different gas – bottom and decompression gases.

• Assuming your dive goes as planned (neither substantially shorter

or longer due to emergency), you should surface with at least one-

third of each gas (your reserve) remaining.

o If less or substantially more remains, recheck your calcula-

tions and/or recalculate your SAC.

o The rule of thirds provides a margin for error in case you

consume gas more quickly than expected, to cover a regu-

lator free flow prior to shutting it down, and to assist a

team mate with a gas supply problem.

• When in doubt, increase your reserve. For instance, increase it

beyond a third if

o conditions may be likely to increase your SAC due to exer-

tion or cold.

o there’s a higher than normal possibility that you’ll slightly

exceed your planned depth/time.

o the dive appears reasonable to make, but your team has

some question about particular variables.

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D. Assuming that anything that can go wrong will, and taking nothing for granted,

forms the basis for planning tec dives.

E. A technical dive plan consists of seven primary segments to consider when

planning.

1. The seven segments are Oxygen, Decompression, Inert gas narcosis,

Gas management, Thermal, Mission, and Logistics. Note that everything

you learn in your training as a technical diver, at all levels, fits into one

of these segments.

2. To help you recall these, remember the phrase “a Good Diver’s Main

Objective Is To Live.”

a. Good – G – Gas management

b. Diver’s – D – Decompression

c. Main – M – Mission

d. Objective – O – Oxygen

e. Is – I – Inert gas narcosis

f. To – T – Thermal exposure

g. Live – L – Logistics

3. Each segment has substeps and considerations that you need to plan and

check before each dive.

4. Good – Gas Management

a. Plan sufficient gas for the dive, plus the reserve, for each diver.

Determine the gas available and compare it to the gas require-

ments.

b. All divers personally analyzed their gas immediately before the

dive.

c. Mark all cylinders appropriately.

d. All cylinders have a second stage at all times (except argon).

e. Test all regulators and valves.

f. Plan for gas termination, malfunction or high consumption.

g. Determine turn pressure for bottom gases.

h. Confirm that team mates have compatible (ideally the same)

gases.

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5. Diver’s – Decompression

a. Calculate the decompression, and compare it to the gas supply

planned.

b. Calculate back-up decompression schedules, or have a back-up com-

puter – all divers have two entirely independent methods for determin-

ing their deco.

6. Main – Mission

a. The entire team understands and agrees to the mission (objective).

b. The mission is reasonably achievable within the dive plan.

c. All team members know their roles and are qualified to perform them.

d. The mission has been made as simple as possible.

e. You can abort the dive at any point, mission notwithstanding.

f. If it would help and is possible, you have practiced the mission on land

or in shallow water first.

g. All team members agree that the primary mission is for everyone to

come back unhurt.

7. Objective – Oxygen

a. The PO2 for the planned max depth and bottom gas 1.4 bar/ata, or less.

b. On gas-switch, extended no-stop dives, the PO2 for the second EANx

blend and depth is 1.4 or less.

c. The PO2 for the planned decompression stops and decompression

gases is 1.6 or less.

d. The oxygen exposure (OTUs and “CNS clock”) for the entire dive

stays within accepted limits.

8. Is – Inert gas narcosis

a. For the planned depth and objective, narcosis will not be a significant

factor.

b. The objective has been simplified as much as possible, and the dive

planned for as shallow as possible.

c. All divers have experience working at the planned depth and in the

conditions present.

9. To – Thermal exposure

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a. Team exposure suits are adequate for the planned duration and

any reasonable contingency extended duration.

b. If using argon in a dry suit, there’s adequate gas for the dive.

c. The team is prepared for the consequences of a major dry suit

failure, if dry suits are used.

d. As part of the predive check, all divers inspect and check dry

suit valves, zippers and seals for integrity and function.

e. If using a wet suit, there’s adequate buoyancy compensation and

insulation to allow for suit compression at depth.

10. Live – Logistics

a. Logistics tend to be extensive and begin well before the dive.

Each of the previous planning segments generates logistical

considerations, most involving who, how, what, where, when.

Note these as you plan; examples include:

b. Establish who is responsible for providing what equipment, gas,

backup gear, etc.

c. Establish who is qualified and will handle surface and underwa-

ter support (if necessary).

d. Establish team dive leaders and project leader.

e. Establish when and where teams will meet.

f. Determine where to find the closest emergency medical facility.

g. Assure that all project members know where to find the first aid

kit, emergency oxygen and other emergency equipment items

know how to use them.

h. Assure that all project members know where to contact help.

i. For big projects, housing, boat access, food and so on may be

considerations.

[Note to students: Use the DSAT TecRec Dive Planning Checklist slates before

dives to review A Good Diver’s Main Objective Is To Live and equipment

requirements.]

F. Predive check– same BWRAF you use for recreational diving, only extended/

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modified for technical diving.

1. Use Begin With Review And Friend, or Being Wary Reduces All Failures.

as your final gear check and readiness. It does not replace A Good Diver’s

Main Objective Is To Live, which you follow for overall, broad tec dive

planning.

2. Being– B – BCD: Confirm connection and proper operation of all valves

for both BCDs (if using a back up) or BCD and dry suit.

3. Wary – W – Weight: Confirm that weight system is properly secured. If

heavy weight diving, confirm ample buoyancy and adequate back up

buoyancy.

4. Reduces – R – Releases: Confirm all releases and straps are secure and

intact (including mask, fins, gauges, stage straps), that all stage/deco cyl-

inders can be cut away, that any large equipment can be released for ditch-

ing easily.

5. All – A – Air (gas): For yourself and team mates, confirm all manifold

valves are all the way open; test breath primary and secondary, confirm

that no equipment is trapping the long hose; confirm that deco cylinders

are pressurized but the valve is closed. It’s common to determine the one-

third-used pressure point for your bottom gas as a turn around pressure

(the pressure at which you head up, or head back to the ascent area –

though you may plan to ascend at a different pressure based on your gas

plan, as discussed earlier).

a. For a simple thirds calculation, divide your SPG pressure by three

and subtract from total to determine when you’ve used the first

third. E.g.. If your SPG reads 210 bar, 210÷3 = 70; 210 - 70 = 140

bar. If it reads 3000 psi, 3000÷3 = 1000; 3000-1000 = 2000 psi.

b. If your pressure isn’t evenly divisible by three, round down to the

next “round” number that is, divide by three and subtract from the

total pressure. E.g.: If pressure is 200 bar, round to 180 bar;

180÷3=60; 200 - 60 = 140 bar. If pressure is 2900 psi, round down

to 2700. 2700÷3= 900; 2900 - 900 = 2000.

6. Failures – F – Final Check: Check each other head to toe looking for loose

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or missing gear. This step finishes in the water with a bubble check and

usually a descent check.

a. Bubble check – Team enters the water and each dunks manifold

below surface. Check each other for bubble leaks at first stage/

valve, in manifold, etc. (In sidemount you check your own cylin-

ders). Same on all stage/deco cylinders. Dive doesn’t commence

until all bubbles leaks, even small ones, are handled. When possi-

ble, also check regulators in the water just under the surface.

b. Descent check – When feasible, after starting descent, team paus-

es at about 6 metres/20 feet and quickly checks:

• for loose gear, correct stage/deco cylinder on top, etc.

• no bubbles (confirm bubble check)

• that everyone is breathing the correct gas (not accidentally

breathing a deco cylinder, for example)

• Descent check may not be feasible until reaching bottom,

due to current, logistics, etc. May submerge and combine

bubble/descent check in very shallow water.

G. Technical diving hand signals

1. Because BCD adjustments, holding a line, etc. may require one hand

constantly, tec hand signals usually only use one hand.

2. Numbers are shown in single digits, one hand [Show students hand sig-

nal for 0 through 9]

a. Show large numbers as digits rather than totals: E.g.., to show

184 bar, you would signal “1,” then “8,” then “4.”

3. In tec diving, thumbs up means more than “up.” It is a command signal

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meaning end the dive now. (To signal, “let’s go up there,” point where you

want to go with index finger.)

4. The second command signal is hold. (To signal, make a fist.) This means

stop everything while sorting through a problem or situation.

5. The third command signal is okay. (Same as in recreational diving.) This

means that you need to confirm that you are okay because your team mate

has concerns about your well being.

6. In tec diving, you usually respond to a signal with the same signal to con-

firm that you understand it. With a command signal, you always return the

command signal.

V. Techniques and Emergencies

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Manual Supported ContentStudy assignment: Tec Deep Diver Manual, pgs 167, When to Make Cylinder

Switches, pgs 162-166, Emergencies III, Tec Exercise 3.3

Learning Objectives


1. What are the guidelines and procedures for when to switch to and from stage/deco

cylinders?

2. What should you do if one of your stage/deco cylinder regulators malfunctions?

3. What should you do if our dive computer fails?

4. What should do if you lose your dive tables?

5. What should do if, on a decompression dive, you have no decompression information at

all?

6. What should you do if you find narcosis affecting you or your team mates’ abilities to

accomplish the mission or dive safely?

7. What should you do if you discover a team mate has separated from you?

A. When to make cylinder switches

1. The guidelines for switching differ somewhat for stage cylinders (used for

added bottom time) and deco cylinders (used for decompression).

a. You won’t be using stage cylinders (only a deco cylinder) as a Tec

40 diver, but it is important to understand the concepts and differenc-

es.

2. Stage cylinders

a. The entire team switches and stages together when any one member

reaches the switch pressure.

b. When using a stage cylinder for gas-switch, extended no stop dives

(Tec 45), you switch when you ascend above the maximum depth for

the gas in the cylinder. (In this case, you handle the stage cylinder

much as you handle a deco cylinder).

c. All switches follow the NO TOX procedure.

3. Decompression cylinders

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a. Your dive plan dictates when you switch to your deco cylinders

• As a Tec 40 diver, it is usually at the first stop.

• When making an accelerated decompression dive (Tec 45

and up), it is usually the first stop depth that requires a dif-

ferent gas – deeper stops may be on back gas.

b. However, you may switch once you ascend above the maximum

depth for the gas and use it as you ascend to the first stop. Eg.

Suppose your first stop is 6 metres/20 feet and you have a cylinder

of EANx50 for decompresion. You may switch to EANx50 after

you ascend above 21 metres/70 feet (maximum deco depth for 50

percent oxygen) and use it as you ascend to 6 metres/20 feet.

c. When using desk top deco software, you can schedule in a one

minute stop at a switch depth deeper than the first required stop to

give you time for the switch. (This is not generally required at the

Tec 40 level because you’re switching for added conservatism.)

d. When staging deco cylinders, all team mates stage together, typi-

cally at the deepest depth you can use the cylinder (PO2 1.6 bar/

ata maximum depth).

e. All switches follow the NO TOX procedure.

B. Stage/deco cylinder regulator failure.

1. A stage/deco cylinder regulator can malfunction and free flow due to dirt/

debris, or due to valve seat failure, etc.

2. This is one reason why you keep the valve closed until needed -- (espe-

cially if you stage the cylinders – to assure there’s still gas in it when you

return).

3. If a stage/deco cylinder regulator free flows:

a. Close the valve.

b. If you suspect dirt/debris and believe you can clear it quickly, do

so.

c. If not, remove the regulator and replace it with another from

another stage/deco cylinder, or the secondary from your back gas if

necessary.

d. Have both the malfunctioned regulator and the switched regulator

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serviced (the switched regulator will get water in it during

the switch).

4. You should always have at least two regulators that fit every stage/

deco cylinder -- the one on it and one you can move to it. (Two DIN

or yoke stage/deco cylinders, or a single DIN stage/deco cylinder to

accept the back set regulator).

5. In some cases, it’s acceptable (but not ideal) to carry a DIN adapter

to make a switch possible, such as moving a DIN back set regulator

to a yoke stage/deco cylinder.

6. In some areas, EANx regulators have special threading – consider

this in your plan.

7. In freezing conditions, a regulator switch may cause two, free flow-

ing regulators. It may be best to shut down the gas and allow the

regulator to rewarm rather than to switch it.

8. If all else fails, you may be able to breathe from a free flowing regu-

lator by briefly opening and closing the valve for each breath.

C. You have several options if you have computer failure, assuming you’ve

properly planned your dive and have the required back ups.

1. In order of preference:

a. If you are still in a no stop situation, abort the dive and sur-

face.

b. Switch to a back up computer for deco information.

c. If there is no back up computer, deco based on your back-up

depth gauge, timer and dive tables (printed from desk top

deco software).

2. In most instances, you abort the dive if your computer fails, because

you’re on your back-up system (some dive with two computers, plus

a backup depth gauge, timer and tables so they still have back-up

with a single failure and therefore can continue the dive).

3. If making a tables-based dive (Tec 45 and up), losing your tables is

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as serious as a computer failure. You have several options:

a. If you are still in a no stop situation, end the dive.

b. Switch to your back up tables. (Plus, you should have your prima-

ry schedule on your slate).

c. If you’ve lost your back up tables, switch to your team mate’s

backup tables (this is one reason you dive with the same gases).

d. If those aren’t available, you and your team mate ascend together

following your team mate’s tables.

D. No decompression information at all on a decompression dive.

1. This shouldn’t happen if you and your team mates dive with the same

gases and carry appropriate back-up computers and/or tables/gauges. A

team of three divers should have six computers/tables between them.

2. If it were to happen, end the dive immediately and start up (if you have

not already), hopefully before reaching your planned bottom time.

a. Think about your planned dive -- you should have some idea of

what the required stops were, such as the deepest stop, the length

of the last stop, when you were going to switch gases, etc.

b. Decompress as best you remember, slightly padding deeper stops.

Heavily pad the last one or two stops.

c. Use up all your remaining decompression gas at the last stop, espe-

cially EANx50 (Tec 40) or oxygen (Tec 45 and up) if you have it.

d. After surfacing, limit activity for several hours, stay hydrated and

monitor yourself for DCS symptoms.

E. Diving below 30 metres/100 feet, most people find narcosis noticeable, but you

should still be able to function normally.

1. Experience with narcosis increases your ability to function with it. Gain

greater depth experience gradually.

2. If narcosis impairs your ability to accomplish your task, or if your team

mate appears or behaves impaired, either ascend to a shallow depth to

continue the dive (if feasible) or end the dive.

3. Be especially alert for signs and symptoms such as looking at your com-

puter or tables and not understanding what they’re telling you, the inabili-

ty to perform simple motor skills (like knot tying) etc. These all alert you

that it’s time to ascend.

4. Some divers use signals to check each other for narcosis, such as asking

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each other for gas pressure. Delayed or confused responses suggest

that narcosis may be an issue.

F. If you discover a team mate missing from you:

1. Remaining team should stay together and search briefly, if appro-

priate.

2. Regroup at a designated point/abort dive -- this should be part of

your Logistics (Live) step in dive planning. If a team mate doesn’t

show after a reasonable period, your plan may call for a brief

search, limits allowing.

3. If you fail to reunite on the bottom, return to the ascent point. You

often regroup there.

4. In some circumstances, a separated team mate may have to ascend

independently under a lift bag or DSMB. Support divers, if pres-

ent, may notify you when they’ve made contact.

5. Do not continue the dive with a broken group -- this violates the

team concept. If after enacting your plans for regrouping you can’t

reunite, the dive should end.

Tec 40 Knowledge Development Threeother Delivery Content, Tec 40-6

Study assignment: Tec 40 Handout 6

I. Managing Oxygen Exposure Continued

Learning Objectives


1. What are Oxygen Tolerance Units (OTUs)?

2. How do you use OTUs to manage oxygen exposure?

3. How do you use the CNS “clock” to manage oxygen exposure?

4. What is the basis for CNS clock surface interval credit?

5. Why may you choose an EANx blend than has a PO2 less than 1.4 at the work-

ing depth for a particular dive?

A. As you already learned, you need to manage your oxygen exposure when

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using EANx (and later oxygen as a Tec 45 diver) to avoid pulmonary and CNS

oxygen toxicity.

1. Recall that your primary prevention of CNS toxicity is in keeping your

oxygen partial pressure below the critical thresholds of 1.4 (working part

of the dive) and 1.6 (decompression at rest).

2. Because it is a biochemical process, there must be an exposure-time rela-

tionship involved with the onset of CNS toxicity. However, there are so

many other physiological variables involved that, for practical purposes,

the relationship is useless for reliably predicting CNS toxicity.

3. Pulmonary oxygen toxicity does have a useful time-exposure relationship

that allows reliable predictions.

a. OTUs (Oxygen Toxicity Units or Oxygen Tolerance Units, depend-

ing upon the reference) and the “CNS clock” both help you pre-

vent pulmonary oxygen toxicity.

b. As a Tec 40 diver, pulmonary oxygen toxicity is highly unlikely,

but possible if you make several dives in a short period using

EANx with high oxygen (like EANx50).

B. OTUs

1. OTUs are units that measure your oxygen exposure as a dose. A given

time at a given PO2 yields a certain number of OTUs based on a simple

mathematical equation.

2. At the Tec 40 level, as you know, you use your desk top decompression

software to calculate your OTUs.

a. You enter the actual gases you use (EANx blend) for your bottom

depth and time, and for your decompression stops and times.

3. OTU limits vary depending upon how much diving you’re doing.

a. The Oxygen Tolerance Units Exposure Limits table in the

Appendix of the Tec Deep Diver Manual shows you the limits

based on the number of days diving.

b. The Total OTUs for Mission is the limit for all OTUs together over

the given number of days.

c. The Average OTUs per day is the maximum allowed in a single

day.

d. Note that at 11 days on, the daily limit is 300 OTUs.

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• Many tec divers use 300 OTUs per day as the limit,

even if diving for fewer than 11 days. This keeps things

simple and conservative.

• You’ll find that 300 OTUs covers a lot of diving – this

is a very workable approach even at higher tec diving

levels.

e. Check your OTUs with your desk top decompression software

after each dive.

C. CNS clock

1. It seems somewhat redundant to calculate the “CNS clock” and

OTUs, but this is the state of practice in tec diving.

2. As you know, you calculate CNS clock with your desk top decom-

pression software. The CNS clock is expressed as a percent of the

allowable exposure – so it should not exceed 100 percent.

a. Most software calculates OTUs and CNS clock simultaneous-

ly.

3. There is oxygen surface interval credit for the CNS clock.

a. Between dives, your body begins reversing the effects of oxy-

gen exposure. This means there is potential for crediting time

at the surface.

b. The basis for CNS surface interval credit is hospital patients

undergoing long term oxygen exposure. The system has a good

field record with use.

c. Most desk top decompression software will credit your CNS

exposure when you plan repetitive dives.

d. The system has variations, so different decompression pro-

grams may give somewhat different results. You can also refer-

ence the CNS Surface Interval Table in the appendix of the Tec

Deep Diver Manual.

e. Note that there is no surface interval credit for OTUs.

4. As always, stay well within CNS and OTU limits.

D. Oxygen exposure and gas blend choice

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1. As you’ve learned, the “ideal” blend for a given dive is the one with a

PO2 near 1.4 at the maximum depth. This is based on the assumption

that you want the maximum possible oxygen so you have the mini-

mum nitrogen (and/or helium as a trimix diver) possible.

2. However, previous oxygen exposure or plans for additional dives may

affect this.

3. To keep oxygen exposure well within limits, you may choose an

EANx blend with a PO2 less than 1.4, even if it means a shorter bot-

tom time or a longer decompression time. This also keeps you well

within PO2 limits.

4. As you gain experience and increase your training as a tec diver, it

becomes increasingly important to consider prior and planned dives

when determining your OTUs and “CNS clock” exposure.

Exercise, other Delivery Content, Tec 40-61. Oxygen Tolerance Units are units that measure your oxygen exposure as a dose.

o True

o False

2. To use OTUs, (choose all that apply):

o a. use software to calculate OTUs based on actual depths, times and gases.

o b. stay within the limits of the Oxygen Tolerance Units Exposure Limits

table.

o c. never exceed 100 OTUs per day.

o d. use your software to calculate OTU surface interval credit.

3. To use the “CNS clock,” (choose all that apply):

o a. use software to calculate CNS clock percent based on actual depths, times

and gases.

o b. you don’t exceed 100 percent.

o c. stay well within limits.

o d. use your software to calculate CNS surface interval credit.

4. The basis for the CNS clock surface interval credit is extensive testing with mili-

tary divers.

o True

o False

5. Even if it were available, you may choose an EANx blend with a PO2 less than

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1.4 at the working depth to

o a. make your decompression more efficient.

o b. reduce oxidative wear on your equipment.

o c. decrease narcosis.

o d. manage your oxygen exposure over several dives.

How did you do?

1. True. 2. a, b. 3. a, b, c, d. 4. False. The basis for the CNS clock surface interval

credit is data from hospital patients undergoing long term oxygen exposure. 5. d.

II. Emergencies Continued


Learning Objectives


1. As a Tec 40 diver, what should you do if you exceed your planned depth and

time?

2. As a Tec 40 diver, what should you do if you have a delay during your ascent?

3. As a Tec 40 diver, what should you if you miss a decompression stop?

4. As a Tec 40 diver, what should you do if you omit decompression?

5. As a Tec 40 diver, what should you do if you run out of gas?

A. This section discusses handling some emergencies within the context of

Tec 40 equipment requirements and limits.

1. The same emergencies can be more serious and more complex to

handle for longer, more complex technical dives.

2. This is another important reason to stay within the limits of your

training and equipment.

B. Exceeding your planned depth and time.

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1. This should be a rare situation caused by unusual circumstances (if you

can’t control your depth under normal circumstances, you’re not ready to

tec dive).

2. Immediately ascend and consult your computer. Your allowable dive time

will likely be much shorter than you planned.

3. If you exceeded your depth significantly and/or for more than a minute,

end the dive immediately.

C. Delay in ascent

1. At the Tec 40 level, a delay in your ascent is not usually a major issue.

2. Your dive computer will calculate the changes in your required decom-

pression, if any.

3. If using a backup table (computer failed), it is not critical if the delay is

short (2-3 min or less)

a. Don’t count the delay as decompression time.

b. Extend your last stop as much as practicable, gas allowing.

D. Missed decompression stop

1. At the Tec 40 level, this is most likely to be caused by failure to control

buoyancy.

2. If you can, redescend and complete the stop, plus one minute, then finish

decompression according to your dive computer.

3. If you can’t redescend, stay at the next stop for the combined time of both

stops. Extend your last two stops (if two or more) by 1.5 what your com-

puter requires, and/or as long as you can with the gas you have.

4. Some dive computers will lock up until you redescend to below the depth

of a required stop. They provide no information in the event that you can’t

return to your deeper stop depth. If you have such a computer or comput-

ers, (see the manufacturer’s instructions), you should have your planned

decompression schedule with you (on a slate, backup tables, etc.) in case

of this kind of emergency.

E. Omitted decompression

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1. Omitted decompression is similar to a missed stop, but involves missing all

required stops and coming all the way to the surface.

2. The risk of DCS is higher than normal, but at the Tec 40 level it should not

be excessive if:

a. you’re using an EANx blend with more oxygen than you’ve set your

dive computers for.

b. you’ve completed most of your decompression using an EANx with

an even higher oxygen content.

3. If you omit decompression for 6 metres/20 feet or less (most likely within

Tec 40 limits), have no symptoms and can return to stop depth in less than a

minute, decompress according to your computer, then extend the last stop as

much as possible.

4. If you omit decompression for 6 metres/20 feet or less (most likely within

Tec 40 limits), have no symptoms and return to stop depth in more than a

minute, extend your 6 metre/20 foot stop by 1.5 times what the computer

requires, and extend the last stop as much as possible.

5. If you omit decompression from deeper than 6 metres/20 feet, return to the

first stop depth. Complete that stop up to and including the 12 metre/40 foot

stop, then extend all subsequent stops by 1.5 times the required decompres-

sion.

6. If you can’t return to depth (no gas available, for instance), breathe oxygen,

remain calm and monitor yourself for DCS symptoms.

7. Some dive computers will lock up if you omit decompression. Others lock

up after a given period (typically a minute), after which they provide no

decompression information. If you have such a computer or computers, (see

the manufacturer’s instructions), you should have your planned decompres-

sion schedule with you (on a slate, backup tables, etc.) in case of this kind of

emergency.

F. The TecRec Emergency Procedures Slate summarizes the procedures for delayed

ascents, missed decompression and omitted decompression. It is recommended that

you carry this slate with you on tec dives.

G. Running out of gas

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1. Should be unlikely at the Tec 40 level if you plan your gas supplies cor-

rectly and follow the reserve rules.

a. Having a deco cylinder with more than ample gas makes this even

less likely.

2. Increased SAC rate due to exertion is not usually an issue, because you hit

turn pressure sooner, which means a shorter dive time and less decompres-

sion.

3. If you run low on gas in a deco cylinder, switch to your back gas. As a

Tec 40 diver, all your decompression should be based on using that gas or

ideally, on one with lower oxygen content.

4. You can share gas with team mates and/or support divers.

5. Generally, if gas termination interferes with your decompression, decom-

press as long as you can, as best as you can. The more you decompress,

the lower your DCS risk. However, do not run out of gas. DCS is serious

but has a high likelihood of successful treatment. Drowning does not.

Exercise, other Delivery Content, Tec 40-71. If you exceed your planned depth and time, as a Tec 40 diver you should consult your

computer and be prepared to end your dive sooner than planned.

o True

o False

2. If you have a delay during your ascent, as a Tec 40 diver (choose all that apply)

o a. you should decompress for 1.5 times what your computer says.

o b. you should decompress for 3 times what your computer says.

o c. continue to decompress according to what your computer says.

o d. None of the above.

3. If you miss a decompression stop, as a Tec 40 diver (choose all that apply)

o a. you should redescend, complete the stop plus one minute, then finish decom-

pression according to your dive computer.

o b. surface and seek immediate recompression.

o c. descend to 12 metres/40 feet and extend all stops by 1.5 times what you com-

puter requires.

o d. you may need to refer to your written decompression schedule if your comput-

ers would lock up.

4. If you omit decompression, what you do depends upon how deep your stops were

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when you had the omission, and how fast you can return to stop depth.

o True

o False

5. If you run out of gas, as a Tec 40 diver your options may include (choose all that

apply)

o a. switching back to back gas.

o b. sharing with a team mate or support diver.

o c. decompressing for as long as possible with what you have to minimize DCS

risk.

How did you do?

1. True. 2. c. 3. a, d. 4. True. 5. a, b, c.

Manual Supported ContentStudy assignment: Tec Deep Diver Manual, pg 204, sidebar, How Do I Figure

1.5 Times with a Computer?

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III. Thinking Like a Tec DiverManual Supported Content

Study assignment: Tec Deep Diver Manual, pg 178, Principles for Surviving a Tec

Dive

Learning Objectives

By the end of this section, you should be able to answer this question:

1. What are six principles of surviving a tec dive?

A. Principles for surviving a tec dive. You’ve been learning these already, but learn

to think about these as survival principles that you never violate, though there may

be different ways to follow them, depending on the environment.

B. The principle of secondary life support -- you should have at least two indepen-

dent usable regulators, at least two independent sources of time, depth and decom-

pression information, and at least two methods for controlling buoyancy. You

should have at least two of anything that keeps you alive. If any one fails, you abort

the dive on the other.

C. The principle of gas reserve -- you should have ample gas to handle reasonably

possible emergencies and still complete your decompression (usually thirds).

D. The principle of self sufficiency -- at any point in a dive, you should be able to

complete it independently.

E. The principle of depth -- your dive plan should account for narcosis, decompres-

sion, oxygen toxicity and gas supply needs based on a planned depth and/or a maxi-

mum contingency depth that you do not exceed.

F. The principle of simplicity -- your dive should be planned as simple as possible,

with complexities eliminated.

G. The principle of procedure and discipline -- you follow the rules and work the

procedures without exception on every dive, no matter how familiar the dive and no

matter how much experience you have.

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Tec 40 Practical ApplicationOn the surface, the practical applications develop skills with procedures related

to gear rigging, using decompression software and dive planning. However, the practical

applications also develop the team thinking and spirit appropriate for technical diving.

To accomplish this, the performance objectives require each team – not just individuals

– to meet the requirements before progressing. This encourages team mates to support

each other and work together. It begins the process of learning that in tec diving, what

one person does can affect everyone, for better or worse. This is why team diving is the

normal practice in tec diving, at all levels.

You may rearrange teams if necessary to avoid one individual carrying the entire

workload, or to avoid a person with significant difficulties holding back the rest inap-

propriately. Otherwise allow teams to develop their own interaction and cooperation in

meeting the challenges you present in the practical applications. Pay attention to be sure

that each person ultimately meets the required performance objectives, but let team

mates help those with difficulty develop their capabilities.

Tec 40 Practical Application oneTo successfully complete this Practical Application, the student should be able to:

1. Working within the student’s assigned team, rig gear so that the equipment of all team mem-

bers conforms with the standardized technical rigging philosophy previously learned, and with

any environment-specific requirements provided by the instructor.

It is recommended that you begin the session by having students watch the

TecRec Equipment Setup and Key Skills video, or assign them to do independently prior

to this session.

Conduct1. Divide the class into teams of two to four individuals.

2. Review proper rigging with a set up kit or kits, including deco cylinder with

markings, mask, fins, gauges, exposure suit, etc. The kit or kits should be in

the configuration(s) that students will be using (Tec 40, Tec 45, etc.) Leave

the kit(s) where students can see it (them), and refer them to their handouts

or the Tec Deep Diver Manual, depending upon the configuration they’re

using.

3. Tell the class that, working as teams, they’re to set up their equipment in an

appropriate configuration modeled on your example and what they’ve pre-

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viously learned.

• Depending on logistics, you may give this as an assignment to be complet-

ed by a specific time for your evaluation, or you can conduct this as a ses-

sion during which all teams work with you and staff supervising.

• Emphasize that they succeed at this exercise as a team or that they go back

and try again as a team. If student divers are not working together, you are

not accomplishing the team objective.

• Encourage discovery learning and team mates helping each other set up the

appropriate configuration.

4. Be available to answer questions and assist with configuration challenges.

5. It is recommended that you have basic clips, tools, labels etc. that students may

need while configuring their gear.

6. When complete, students present their kits as teams for you to assess. Note

any discrepancies and have the team correct them and then present their rigs

again as a team. It is acceptable to stipulate that no one in the team is done until

everyone in the team has successfully set the kit appropriately.

7. Tip: Schedule Tec 40 Practical Application I to immediately precede Tec 40

Training Dive One, with time for remediation and adjustments. This gets every-

one’s equipment set up for the dive, and assures that team mates are familiar with

each other’s gear.

Tec 40 Practical Application TwoTo successfully complete this Practical Application, the student shouldbe able to:

1.Explain and demonstrate the basic features and operation of a desk top decompression

software.

2. Calculate the student’s working SAC rate based on the data during the SAC swim in

Tec 40 Training Dive One.

3. Plan a decompression dive within Tec 40 limits by planning/calculating gas require-

ments, maximum depth, exposure suit requirements, methods for meeting an objective,

turn pressure and other particulars based on information provided by the instructor

(which may include a particular decompression schedule, gases or cylinders available,

dive objective and environmental details). The plan should appropriately and accurately

account for all segments of the A Good Dive’s Main Objective Is To Live dive planning

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segments.

4. Working as part of a team and with instructor guidance, think backwards through the

dive from the furthest point imagining realistic problems that could come between the team

and surfacing safely, and formulating realistic solutions for each and making them part of

the dive plan. The team must draft a list of the problems and solutions.

Conduct1. Divide the class into teams of two to four individuals. Unless there are personali-

ty conflicts or other issues, it is usually desirable to retain the same teams from pre-

vious sessions. This is particularly true if they have bonded well and function well

as a team.

2. Demonstrate one or more types of desk top decompression software, showing

students how to launch the program, enter settings and plan a Tec 40 level dive

similar to what they will be making. Allow teams to use and play with the soft-

ware (if necessary due to equipment available, may be done in turns, with some

teams working on other parts of this Practical Application while others use the soft-

ware).

3. Assign each team a Tec 40 level dive to plan using desk top decompression soft-

ware and accounting for all steps of the a Good Diver’s Main Objective Is To

Live dive planning steps based on information you provide.

• You may tell students this plan will be the basis for Tec 40 Training Dive Two,

with the mission accomplishing the assigned skills, and equipment, environment

and other specifics based on actual.

• Give students a maximum depth and time (they may have to reduce them to

stay within 10 minutes decompression or meet gas volume requirements). If this

will be the basis for Dive Two, tell them that the actual dive will be a shallower

and longer no stop dive.

• Have them use their TecRec Dive Planning Checklists. The Dive Planning Slate

may be used to record data from desk top decompression software.

• Since they don’t have data for their decompression SAC rates, assign a deco

SAC rate. A suggested assigned rate is to use two-thirds of their working rate.

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• With most software, divers have to determine their own turn pressures. Have

students do this based on the gas volumes they calculate and the cylinder(s)

they will be using. Students who have more difficulty with math may require

more time – encourage team mates to help each other, but not to do it for each

other.

• Show students how they would use software to calculate their oxygen expo-

sure (OTUs/CNS clock) by entering the actual depths, times and gases used

on the dive.

• You may schedule this practical application so that it is also the predive plan-

ning for Tec 40 Training Dive Two, and brief students accordingly for plan-

ning purposes.

4. As part of the planning process, think backwards through the dive from the

furthest point imagining realistic problems that could come between the

team and surfacing safely, and formulating realistic solutions for each, and

making them part of the dive plan. Have students provide you with a list of

problems and solutions.

• Review the list and note any additional problems they may not have

thought of. Ask them for solutions to these.

Tec 40 Practical Application ThreeTo successfully complete this Practical Application, the student should be able to:

1. Calculate the student’s decompress SAC rate based on the data during the SAC swim

in Tec 40 Training Dive Two (if not completed during dive debriefing).

2. Working as part of a team and with minimal instructor guidance, plan two decompres-

sion dives within Tec 40 limits according to the principles learned in this course, accu-

rately accounting for all segments of the A Good Dive’s Main Objective Is To Live dive

planning segments.

3. Working as part of a team and with instructor guidance, think backwards through both

planned dive from the furthest point imagining realistic problems that could come

between the team and surfacing safely, and formulating realistic solutions for each and

making them part of the dive plan. The team must draft a list of the problems and solu-

tions.

Conduct

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1. Divide the class into teams. Unless there are personality conflicts or other issues,

it is usually desirable to retain the same teams from previous sessions. This is par-

ticularly true if they have bonded well and function well as a team.

2. Assign each team two Tec 40-level dives to plan using desk top decompression

software and accounting for all steps of the A Good Diver’s Main Objective Is

To Live dive planning steps based on information you provide.

• It is recommended that students plan Tec 40 Training Dives Two and Three.

• Tec 40 Training Dive Two is a no stop dive but simulates a decompression dive.

Tell students to write down the decompression that the software predicts based

on a simulated maximum depth (actual dive depth can be shallower).

• Provide students information that they will need to plan the dives (maximum

depths, maximum times, gas blends available, equipment available, environ-

mental conditions, etc.)

• Tec 40 Training Dive Three is an actual decompression dive that students will

plan and make.

• Have students use their TecRec Dive Planning Slates and Checklists.

• Students should now have their decompression SAC rates and can recalculate

and confirm their working SAC rates based on information they gathered in Tec

40 Training Dive Two.

• Students should be able to plan all aspects of a Tec 40 level dive with only brief

reminders and minimal guidance from you and your staff.

• Remind students to consider repetitive dive exposure (nitrogen and oxygen)

depending upon the scheduling of these two dives, as well as the previous two

training dives.

• Students should be able to provide you with a decompression schedule (per

software) gas use, reserves, turn pressure, oxygen exposure (CNS and OTUs)

for each diver, descriptions of all required/planned equipment (cylinder sizes

and markings), logistics and general emergency procedures specific to the envi-

ronment.

3. As part of the planning process, have students think backwards through

the dives from the furthest point imagining realistic problems that could

come between the team and surfacing safely, and formulating realistic solu-

tions for each, and making them part of the dive plan.

4. Review the dive plans for thoroughness, omitted information and errors. When

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all teams have finished, share the completed plans with the group, discussing the

merits and ideas within them.

Tec 40 Training DivesTec 40 Training Dive oneDive Today Considerations

Students may complete Tec 40 Training Dive One before completing Tec 40

Knowledge Development One or Tec 40 Practical Application One. In this instance, follow

these guidelines.

1. Have equipment set up prior to the dive, or assist with setup. Students must still

set up their own gear later in Tec 40 Practical Application One. Briefly explain what each

component of the rig is for and why it is configured that way.

2. Thoroughly brief all the skills, with more detail than you might normally give in

terms of the purpose of the skill. Students will read about this in more detail when they

complete Tec 40 Knowledge Development One, but it is important from the outset that they

know when and why they would use a particular skill they are learning.

3. Since they have not completed any prior sessions, students may not be aware of

the role team work plays in tec diving. Assign student divers to teams and emphasize the

need to work as a team, think as a team and support each other as a team.

4. After Tec 40 Training Dive One, students must complete Tec 40 Knowledge

Development One before moving on to Knowledge Development Two, Tec 40 Practical

Application One before moving on to Practical Application Two, and all of these before

moving on to Tec 40 Training Dive Two.

To successfully complete this training dive, the student must be able to:

1. Working in a team, assemble and inspect the basic technical diving rig following the pre-

viously described rigging philosophy and to meet individual/environmental needs.

2. Demonstrate the proper weight required for the dive.

3. Demonstrate neutral buoyancy while wearing the basic technical dive rig(Tec 40, full

standardized rig or sidemount) underwater in water too deep in which to stand by hovering

for 1 minute without sculling or kicking.

4. Within 30 seconds, independently close the cylinder valve to a regulator that is experienc-

ing a simulated free flow.

5. Assist a team mate by closing the correct valve to a regulator that is experiencing a simu-

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lated free flow.

6. Within 30 seconds, independently close the isolator valve in response to a simulated

manifold leak. (Simulated closing is permitted if performing the skill with a single

equipped with an H or Y valve, or with a pony bottle. The skill is not required if using

sidemount.)

7. Respond to a simulated out of gas emergency by signaling a team mate, switching to

the team mate’s long hose second stage, then swimming 30 metres/100 feet using the long

hose regulator and maintaining contact with the team mate.

8. Respond to a team mate’s simulated out of gas emergency by, on signal, providing the

team mate with the long hose second stage, switching to the short hose secondary, then

swimming 30 metres/100 feet as the team mate uses the long hose regulator, maintaining

contact.

9. Working in a team, perform a bubble check, descent check and S-drill.

10. Independently don, remove and re-don a stage/deco cylinder on the bottom.

11. Perform gas switches to stage/deco cylinders correctly following the NO TOX proce-

dure.

12. Shut down both manifold valves and the isolator valve, and switch second stages to

maintain a breathing supply, beginning with any valve chosen by the instructor, within 60

seconds (or within 40 seconds if there is no isolator valve).

13. Deploy a lift bag or DSMB from the bottom in water too deep in which to stand.

14. Swim at a steady pace at a constant depth for sufficient time to determine the SAC

rate.

15. Using only neutral buoyancy, maintain a simulated decompression stop for eight min-

utes.

16. Remove and replace stage/deco cylinder at the surface in water too deep in which to

stand.

I. Training Dive StandardsA. Tec 40 Training Dive One is conducted in confined water or limited

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open water. (See Section Two, Course Standards for definitions of these.)

The maximum depth is 10 metres/30 feet. It is a no decompression

dive. It is recommended that the site provide ready access to water shal-

low enough in which to stand, and have an intermediate depth (approx.

half the maximum depth) for simulating breathing high oxygen only at a

shallow depth.

1. Note that this is a moderately long dive with gas sharing and simu-

lated free flows. Especially using single cylinder Tec 40 kits, stu-

dents may exhaust their air supply before completing all required

skills. It is recommended that you use as shallow a depth as possi-

ble and have fills or extra cylinders available if necessary.

B. Ratios – 6 students to 1 instructor, with 2 more students permitted

with a certified assistant to a maximum of 8. (See Section Two for spe-

cific requirements necessary to qualify as a certified assistant in this

course.) These are maximums – reduce ratios as necessary to accommo-

date student characteristics and environmental/logistical variables.

C. Students and instructor must be equipped as described in Tec 40

Knowledge Development One (Tec 40 kit, standardized technical rig

or sidemount) with accommodation for environmental needs. This

includes a decompression cylinder. It is recommended that each student

have an individual cylinder, but acceptable for students to share cylinders.

1. The ideal is for the instructor to wear the same kit as students.

2. The instructor may wear the standardized technical rig. This is rec-

ommended if a Tec 40 class has mixed configurations (some in

standardized technical rig, others in a basic Tec 40 kit). Skills in

the Tec 40 kit differ little from the same skills in the standardized

technical rig.

3. If a class has sidemount and backmount configurations, for demon-

stration purposes it is recommended that both configurations be

represented, with the instructor wearing one and a certified assis-

tant wearing the other.

D. Gas requirements: Students and staff may use air or enriched air, any

suitable blend up to EANx50, in sufficient supply to accomplish the dive

performance objects and have free time for experience and practice. It is

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recommended that the stage/deco cylinder have a richer EANx blend than

the back gas cylinders. You may have students simulate using different

EANx blends.

II. Predive Planning, Briefing and Preparation– suggested sequence

A. Predive briefing

1. Students set up their rigs, but do not yet don exposure suits (gear

may already be set up from the Practical Application – if following

Dive Today, it’s recommended that you have rigs already set up.

Go over the configuration(s) in detail, because they will not have

been informed about this yet.)

a. Inspect each rig for correct setup, ample gas, proper cylin-

der labels, etc.

b. Have divers work in teams. No one in the team is ready

until everyone in the team is ready.

2. Dive site overview

a. Depth, temperature, entry/exit points, note worthy features.

b. Facilities – parking, lockers, boat dry and wet areas, where

to find emergency equipment, etc.

B. Dive overview

1. Depth/time limits (limited open water) – if appropriate, note that

the dive may actually be two dives if gas fills are needed to get

everything done.

2. It’s recommended that you have students list the dive plan on their

slates – times, depths, turn pressures, etc., plus the skills, in order,

to consult during the dive. Get them in the habit of doing this for

each dive.

3. Skill overview – describe each skill, the performance requirement

and how you’ll conduct it, including signals you will use, etc.

a. proper weighting

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b. neutral buoyancy – hovering

c. regulator free flow – valve shutdown

d. regulator free flow – team mate assist

e. manifold leak – isolator shutdown

f. manifold leak – team mate assist

g. out of gas – use long hose as receiver

h. out of gas – use long hose as donor

i. bubble check, descent check and S-drill

j. don, remove and replace stage/deco cylinder on bottom

k. NO TOX gas switch

l. gas shutdown drill

m. deploy lift bag/DSMB

n. SAC swim at constant depth

o. simulated decompression stop

p. remove and replace stage/deco cylinder in water too deep

in which to stand

q. recheck weight with near empty cylinders

4. Review hand signals, emergency protocols, descent and ascent pro-

cedures, entry and exit procedures and any final details

a. Predive check is general only – technical level BWRAF is

okay; students learn the broader technical diving predive

check in the next session.

b. It’s recommended that you spot check everyone’s gear after it

is donned.

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III. Tec 40 Training Dive one – suggested sequenceA. Entry – into water shallow enough in which to stand (no deco cylinder at

this point).

1. Divers check their weight (no deco cylinder)

2. If using heavy rigs, divers may be negative with zero weight –

explain that they’ll recheck at the end with near empty cylinders

B. Descent to insensitive bottom (limited open water)

1. Students perform descent check and bubble check; check each

other for loose gear, etc.

2. Position class for skills.

C. Dive skills – for each, instructor demos, then has students perform as

briefed.

1. neutral buoyancy – hovering for 1 minute, no sculling or kick-

ing

a. Recommended that you use a line for reference and con-

trol if necessary.

b. Even very experienced recreational divers may need some

practice in learning to control buoyancy with heavy tech-

nical gear, especially in standardized technical rig.

c. Emphasize relatively horizontal position in the water

(ideal deco position)

2. regulator free flow – valve shutdown independently, within 30

seconds

a. Simulate by holding the purge button of either second

stage. Student closes the correct valve (pay close attention

to gas supplies, esp. with single cylinders and pony bot-

tles)

b. Emphasize that you may need to loosen waist strap and/or

crotch strap during your demo, then retighten when done.

3. regulator free flow – team mate assist

a. Simulate by holding the purge button of either second

stage. Student signals team mate to shut down the correct

valve. Again, pay attention to gas supplies.

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4. manifold leak – isolator shutdown independently within 30 sec-

onds

a. Simulate by pressing the purge button of your regulator

behind the student’s head so student can hear air flow, off to

one side or other.

b. Student shuts down isolator independently.

c. To simulate with no isolator on high capacity single, student

closes the valve to the short hose, then reopens it immediate-

ly (to allow for next step.)

d. Student leans back and looks up to find leak and checks sig-

nal to determine leaking side [identify side via a signal.]

Student switches (if necessary) to the regulator on leaking

side.

[Note, optional skill for sidemount students: The sidemount equivalent of

isolator shutdown is to transfer a working regulator to the other cylinder to

replace a malfunctioning regulator. The ideal is to have sidemount students

do this independently underwater in water shallow enough in which to

stand. However, that generally requires the transferred regulator to be over-

hauled afterward. Alternatively, they can practice at the surface with masks

on and breathing from the regulator only, but with the valves and first stages

out of the water.]

5. manifold leak – team mate assists

a. Simulate by pressing the purge button of your regulator

behind the student’s head so student can hear air flow, off to

one side or other.

b. Student signals team mate to assist. Team mate closes isola-

tor and tells the diver which side the leak is on.

c. To simulate with no isolator for high capacity single, assist-

ing student puts hand at valve location and simulates as if

closing valve (does not actually close a valve). The hand

must reach all the way to where the valve would be. For side-

mount students, it is recommended, but not required, that

they assist a staff member or student in a doubles setup.

d. Student switches (if appropriate to simulated scenario) to the

regulator on the leaking side.

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6. out of gas – use long hose as receiver, swim horizontally 30

m/100 ft.

7. out of gas – use long hose as donor, swim horizontally 30 m/100

ft.

8. Students return to surface/shallow area (change/refill all cylinders if

necessary). Enter/re-descend.

a. Descent check – on the bottom is acceptable

b. S-drill -- in teams, divers perform long-hose sharing as donor

and receiver, swimming about 6 m/20 ft.

c. Reposition class for skills demos and practice

9. Don, remove and re-don stage/deco cylinder on bottom

a. Cylinders are placed on the bottom by staff (or hand carried

by students) before exercise.

b. No gas switches.

c. Left side, single cylinder only.

10. Gas switch – NO TOX

a. Teams swim to shallow water (if available – if level depth,

designate one area as “shallow enough to breath EANx50”)

and perform NO TOX switch to their stage/deco bottles with

actual or simulated EANx50.

b. Check for clipping off long hose second stage, and be sure

that team mates check each other at the “X” step.

11. Gas shut down drill – on bottom, students close and reopen both

regulator valves and isolator valve, switching second stages to

stay with the open valve, within 60 seconds (if no isolator valve

for high capacity single, within 40 seconds)

a. Signal each student to perform shutdown drill, and indicate

where to start (long hose, short hose or isolator).

b. Student closes and opens all valves, one at a time beginning

with the one you indicate, and switches second stages to stay

on the open valve.

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c. Mix up which valve you have students start with.

d. Again, simulate an isolator with single cylinder by having

student close and immediately reopen the other (whichever

one the student has not immediately opened or closed) regu-

lator valve.

e. It may take more than one try to do this within 60 seconds.

f. Confirm all valves are open at end of exercise.

12. Deploy lift bag/DSMB

a. After your demonstration, all students practice retrieving

bags and reels, and sending up bag and/or DSMB. Watch for

correct technique that avoids entanglement.

b. If conducting the dive in a pool, do this in the deepest water

possible.

c. Stay close to the diver practicing the skill in case you need to

prevent an ascent – buoyancy control problems are common

when learning this skill.

13. SAC swim at constant depth

a. Teams swim together at a slow, steady pace (with stage cylin-

der) at as level a depth as possible long enough to determine

SAC rate (the shallower they are, the longer the swim).

b. Be sure students note their beginning and ending pressures

and time, and the depth on a slate.

14. Free time for practices and surprise drills

a. Team mates practice skills together. Encourage practice by

spontaneously having students perform the skills they’ve just

learned.

b. Allow plenty of time here – this is also a good time for addi-

tional surprise drills, such as pretending you’re out of gas,

etc.

15. Ascent – in water too deep in which to stand. Watch that students

control their ascent rates (more expanding air in BCDs with heavy

rigs may be an issue). Repeat if necessary until students can control

their ascent rates without difficulty.

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16. Simulated decompression stop – students ascend to a stop depth

you designate (1.5 metres/4 feet recommended) and maintain the

depth for eight minutes.

a. Divers should use only buoyancy control to maintain stop

depth, but you may provide a visual reference for them.

b. Remind students that they should remain within approxi-

mately .5 metres/1.5 feet of stop depth.

c. Remind students to maintain a roughly horizontal position

with their chests at stop depth.

d. This is a difficult skill, especially the first time. If possible,

allow extra practice time beyond eight minutes.

e. Time allowing, have students also practice a NO TOX gas

switch while maintaining stop depth with buoyancy control

only.

17. Student divers remove, replace and then re-remove stage/deco

cylinders at the surface.

a. Students commonly find this more difficult at the surface

than underwater, which is why they learn it first underwater.

b. Some students may find it easiest to remove the hip clip

first at the surface.

18. Recheck weight with near-empty cylinders and no deco cylinder.

a. Students wearing a heavy standard technical rig may be sur-

prised at how much weight they need.

b. Students in single cylinder rigs or light doubles may find

little more weight is needed.

D. Surface and exit – simulate technique that will be used in open water dives

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IV. Post DiveA. Performance review. After a moment to rest, get a drink, etc., but imme-

diately while all memories are fresh, have teams identify what happened,

mistakes, what worked, what didn’t, what they learned, etc. Comment

and fill in missing information as necessary, but have students critique

themselves constructively while you guide the process.

B. Confirm that all divers have their SAC swim data.

C. Divers disassemble and stow equipment.

D. Students log dive for your signature.

E. Remind students of assignments/tasks before the next scheduled meeting

(knowledge development, etc.)


To successfully complete this training dive, the student must be able to:

1. Working in a team, 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 procedure.

2. Independently don and remove a single deco cylinder at the surface.

3. Descend along a line to the bottom, maintaining control of depth and descent speed

by adjusting buoyancy.

4. Working as a team, perform appropriate bubble checks and descent checks.

5. While continuously swimming, independently stage a deco cylinder, swim at least 10

metres/30 feet from it, return to it and don it.

6. Swim at least two minutes and a distance of 18 metres/60 feet sharing gas with the

long hose as both the donor and the receiver.

7. Perform the gas shutdown drill within 60 seconds (40 seconds if not wearing isolator

doubles).

8. Perform a working rate SAC swim by swimming for approximately five minutes at a

level depth, recording the appropriate information for later calculation.

9. Demonstrate time/depth and gas supply awareness by writing the depth and time at

each 35 bar/500 psi of back gas consumed.

10. Demonstrate turn pressure and time limit awareness by signaling the instructor

upon reaching the turn pressure or time limit the team had planned were this really a

decompression dive.

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11. As a team, deploy a lift bag/DSMB from the bottom.

12. As a team, simulate a partially failed lift bag/DSMB by deploying a second lift bag/

DSMB up the line of the first lift bag.

13. Use primarily proper buoyancy control to ascend along a line at a controlled rate not

to exceed 10 metres/30 feet per minute, or slower if specified by a dive computer, to stop

at a simulated decompression stop at 5 metres/15 feet, without ascending past it.

14. Record the appropriate information for later calculation of a deco rate SAC by simu-

lating a 10 minute required decompression stop at 5 metres/15 feet.

15. While neutrally buoyant at a simulated decompression stop, with a team mate, NO

TOX gas switch to decompression cylinder while maintaining depth within 1 metre/3 feet

of the stop depth.

16. Throughout the dive, respond appropriately to simulated emergencies prompted by the

instructor.

17. Post dive, use desk top decompression software to determine the oxygen exposure

(OTUs and CNS “clock”) of the dive as it was actually made.

I. Training Dive StandardsA. Tec 40 Training Dive Two is conducted in open water. (See Section

Two, Course Standards for definitions of these.) The minimum depth is

10 metres/30 feet and the maximum depth is 18 metres/60 feet. It is a

no decompression dive.

1. 10 metres/30 feet to 12 metres/40 feet is recommended for larger

classes with students in single cylinders to provide adequate time

to accomplish all skills.

B. Ratios – 6 students to 1 instructor, with 2 more students permitted

with a certified assistant to a maximum of 8. (See Section Two for spe-

cific requirements necessary to qualify as a certified assistant in this

course.) These are maximums – reduce ratios as necessary to accommo-

date student characteristics and environmental/logistical variables.


Knowledge Development One (Tec 40 kit, standardized technical rig

or sidemount) with accommodation for environmental needs. This

includes a decompression cylinder. It is recommended that each student

have an individual cylinder, but it is acceptable for students to share cylin-

ders.

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2. The instructor may wear the standardized technical rig. This is recom-

mended if a Tec 40 class has mixed configurations (some in standard-

ized technical rig, others in a basic Tec 40 kit). Skills in the Tec 40 kit

differ little from the same skills in the standardized technical rig.

3. If a class has sidemount and backmount configurations, for demonstra-

tion purposes it is recommended that both configurations be represent-

ed, with the instructor wearing one and a certified assistant wearing

the other.

D. Gas requirements: Students and staff may use air or enriched air, any suit-

able blend up to EANx50, in sufficient supply to accomplish the dive perfor-

mance objectives and have free time for experience and practice. It is recom-

mended that the stage/deco cylinder have a richer EANx blend than the back

gas cylinders. You may have students simulate using different EANx blends.


A. Predive briefing

1. Students set up their rigs, but do not yet don exposure suits

a. Inspect each rig for correct setup, ample gas, proper cylinder

labels, etc.

b. Have divers work in teams. No one in the team is ready until

everyone in the team is ready.


a. Depth, temperature, entry/exit points, noteworthy features,

etc.

b. Facilities – parking, lockers, boat dry and wet areas, where to

find emergency equipment, etc.

B. Dive overview

1. You may schedule Tec 40 Practical Application Two immediately

before this dive and integrate the dive planning and preparation for this

dive with the dive planning assignments in the practical application.

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2. Depth/time limits

3. It’s recommended that you have students list the dive plan on their

slates – times, depths, turn pressures, etc., plus the skills, in order, to

consult during the dive. Get them in the habit of doing this for each

dive.

4. Dive and skill overview – describe how the overall dive will go, detail-

ing each skill, the performance requirement and how you’ll conduct it,

including signals you will use, etc.

a. don and remove a single deco cylinder at the surface

b. controlled descent

c. bubble check and descent check

d. stage and retrieve deco cylinder on the fly

e. swim two minutes sharing gas as donor and as a receiver

f. gas shutdown drill – 60 seconds (40 if not wearing isolator

doubles)

g. open water SAC swim (five minutes)

h. time/depth and gas supply awareness

i. turn pressure/time limit awareness

j. lift bag/DSMB deployment

k. second lift bag/DSMB deployment

l. ascent to simulated decompression stop

m. 10 minute SAC decompression

n. NO TOX gas switch while neutrally buoyant

o. simulated emergencies

5. Review hand signals, emergency protocols, descent and ascent proce-

dures, entry and exit procedures and any final details

a. Predive check – teams should check each other using the DSAT

TecRec Dive Planning Checklist slates, technical level BWRAF

included.

b. It’s recommended that you spot check everyone’s gear after it

is donned.

c. Per team, no one is ready until everyone is ready.

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III. Tec 40 Training Dive Two – suggested sequenceA. Entry – appropriate for local environment.

1. Divers check their weight (if necessary -- no deco cylinder during

check).

2. Don and remove deco cylinder at the surface (if each diver has a

deco cylinder [recommended], then divers may don their cylinders

after entering the water and remove them at the end of the dive

before exiting).

3. Bubble check at surface (may be combined with descent check if

surface conditions are somewhat choppy).

B. Descent

1. Students descend using buoyancy to maintain a controlled rate

along a line, staying in teams and maintaining team contact.

2. Position class for skills on insensitive bottom.

C. Dive skills – instructor demos new skills or if necessary to remediate per-

formance only. Students perform on signal as briefed.

1. Bubble check (if not performed at surface) and descent check

a. Before dive, quietly assign one or two students to have

minor “problems” (e.g. loose crotch strap,) for team mates

to catch.

2. Stage and retrieve cylinder on the fly – instructor demonstrates

first, the students practice.

a. Confirm closed valve, tucked hoses and unclipping cylinder

while swimming to stage point.

b. Stage cylinder and secure in place (eg clip to line along

bottom) – reduce buoyancy at the same time as releasing

the cylinder – pausing only momentarily and without mak-

ing bottom contact.

c. Swim approximately 10 metres/30 feet and return.

d. Prepare to adjust BCD while approaching cylinder.

e. Without making bottom contact, release and grab cylinder;

increase buoyancy to compensate for added weight at the

same time.

f. Clip in cylinder while continuing to swim.

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3. Swim two minutes sharing gas as donor and receiver.

a. Skill starts with receiver giving out of gas signal and donor

deploying long hose and switching to secondary regulator

b. Have students swim a circle or other closed pattern at a

level depth while sharing gas with the long hose; receiver

leads.

c. After two minutes, students switch roles and repeat drill.

4. Gas shutdown drill – 60 seconds (40 if not wearing isolator SAC

swim).

5. Open water SAC swim – in teams, students swim for five minutes

at a level depth gathering cylinder pressure, depth and time infor-

mation to calculate bottom SAC rate.

6. Time/depth and gas supply awareness – on a slate, divers should

record the depth and time for each 35 bar/500 psi consumed for the

entire dive, amid other skills as necessary.

a. Team mates may remind and assist each other.

7. Turn pressure/time limit awareness –students signal you and their

team mates when they reach the turn pressure or dive time based on

the simulated decompression dive they calculated.

a. Remind students that because this is a no stop dive, the dive

will continue until reaching the actual limits of. [reinforce

planned actual dive time/gas supply limits]

8. Lift bag/DSMB deployment – on your signal one diver from team

deploys lift bag/DSMB to surface. Teams should decide who this

will be during dive planning.

9. Second lift bag/DSMB deployment – on your signal, a second

diver in each team deploys a lift bag/DSMB and sends it up the

same line to simulate adding buoyancy to a partially failed bag/

DSMB, or sending up a second bag as an emergency signal.

10. Ascent to simulated decompression stop – divers ascend at 10

metres/30 feet per minute or slower if indicated by their computers.

a. Depending upon the circumstances, you may have them

ascend along their lift bag/DSMB line or a heavier line like

a mooring line or anchor line.

b. Divers should control buoyancy so they arrive at 5

metres/15 feet neutrally buoyant, and not rise past the stop.

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11. 10 minutes SAC decompression stop – students remain at 5 metres/15

feet simulating a decompression stop and recording time/gas supply

information for calculating their decompression SAC rate later

a. Divers should use primarily buoyancy control to maintain stop

depth, but may use a line or other object for assistance.

b. Remind students that they should remain within approximately .5

metres/1.5 feet of stop depth.

c. Remind students to maintain a roughly horizontal position with

their chests at stop depth.

12. NO TOX gas switch while neutrally buoyant – one at a time but as a

team, students switch to a deco cylinder following the NO TOX proce-

dure, maintaining the stop depth plus or minus 1 metres/3 feet, using

neutral buoyancy to control depth.

a. Team mates may assist each other with depth control.

b. Follow the entire NO TOX procedure.

c. If students have individual deco cylinders, you may have them do

the switch before the 10 minute SAC deco and use their deco cyl-

inders for the entire simulated decompression.

d. If students do not have individual deco cylinders, they may take

turns using cylinders (at least two, one each for two team mates)

carried by the instructor/staff.

13. Simulated emergencies – tell students that depending upon time, gas

supplies, etc, throughout the dive you may surprise them with impromp-

tu emergencies via hand signals or your slate that they must respond to

appropriately. Simulate situations students should already be prepared to

deal with based on their training to this point.

D. Surface and exit – technique suited to environment. Students wearing deco cyl-

inders remove them in the water.

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IV. Post DiveA. Performance review. After a moment to rest, get a drink, etc., but imme-

diately while all memories are fresh, have teams identify what happened,

mistakes, what worked, what didn’t, what they learned, etc. Comment

and fill in missing information as necessary, but have students critique

themselves constructively while you guide the process.

B. Confirm that all divers have their SAC swim data.


D. Divers calculate their OTUs and CNS clock based on the actual dive

as made (actual times, depths and EANx blend(s)) used.

1. Provide guidance, but encourage team mates to help each other.

2. You may do this at the beginning of Tec 40 Practical Application

Three if necessary for logistics.

E. Students log dive for your signature.

F. Remind students of assignments/tasks before next scheduled meeting

(knowledge development, etc.)

Tec 40 Training Dive ThreeTo successfully complete this training dive, the student must be able to:

1. Working in a team, 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 procedure.

2. Complete a simulated decompression dive based within Tec 40 limits (40 metres/130

feet max depth, 10 minutes max deco, EANx50 max oxygen content).

3. Descend along a line to the bottom, maintaining control of depth and descent speed

by adjusting buoyancy.


5. Perform the gas shutdown drill within 45 seconds (30 seconds if not wearing isolator

doubles).

6.. Demonstrate time/depth and gas supply awareness by writing the cylinder pressure

at each 10 minutes of dive time.

10. Demonstrate turn pressure and time limit awareness by signaling the instructor

upon reaching the turn pressure or time limit the team had planned were this really a

decompression dive.

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11. As a team, deploy a lift bag/DSMB from the bottom.

12. Ascend the lift bag/DSMB line and complete the simulated decompression, staying togeth-

er with the team, remaining neutrally buoyant and staying within plus or minus .5 metres/1.5

feet of stop depth by controlling buoyancy.

13. Throughout the dive, respond appropriately to simulated emergencies prompted by the

instructor.

I. Training Dive StandardsA. Tec 40 Training Dive Three is conducted in open water. (See Section Two,

Course Standards for definitions of these.) The minimum depth is 15

metres/50 feet and the maximum depth is 27 metres/90 feet. It is a no

decompression dive.

1. Students will simulate a dive requiring decompression.

B. Ratios – 4 students to 1 instructor, with 2 more students permitted with a

certified assistant to a maximum of 6. (See Section Two for specific require-

ments necessary to qualify as a certified assistant in this course.) These are

maximums – reduce ratios as necessary to accommodate student characteristics

and environmental/logistical variables.


Knowledge Development One (Tec 40 kit, standardized technical rig or

sidemount) with accommodation for environmental needs. This includes a

decompression cylinder. It is recommended that each student have an individ-

ual cylinder, but acceptable for students to share cylinders.


2. The instructor may wear the standardized technical rig. This is recom-

mended if a Tec 40 has mixed configurations (some in standardized

technical rig, others in a basic Tec 40 kit). Skills in the Tec 40 kit differ

little from the same skills in the standardized technical rig.

3. If a class has sidemount and backmount configurations, for demonstra-

tion purposes it is recommended that both configurations be represent-

ed, with the instructor wearing one and a certified assistant wearing the

other.

D. Gas requirements: Students and staff may use air or enriched air, any suitable

blend up to EANx50 or that reaches 1.4 at the maximum planned depth, which-

ever is less, in sufficient supply to accomplish the dive performance objects and

have free time for experience and practice.

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1. It is recommended that students have decompression cylinders. Have

students practice carrying a gas blend that they cannot safely breathe at

the simulated maximum depth (the gas content may be simulated; have

students label cylinders “Simulated EANxXX, Max Depth XX; Actual

EANxXX, Max Depth XX)


A. Predive briefing

1. Students set up their rigs, but do not yet don exposure suits


labels, etc.




a. Depth, temperature, entry/exit points, noteworthy features, etc.

b. Facilities – overview parking, lockers, boat dry and wet areas,

where to find emergency equipment, etc.

B. Dive overview

1. It is recommended that you schedule Tec 40 Practical Application Three

immediately before this dive and integrate the dive planning and prepa-

ration for the dive with the dive planning assignments in the practical

application.

2. Depth/time limits (limited open water) – students plan for simulated

depth, time and decompression, and actual maximum depth and time you

provide (no decompression).

Note: Because this is actually a no decompression dive, dive computers

will not provide deco information. Students need to have the sim-

ulated decompression schedule (written on a slate or printed and

laminated tables) to follow.

3. It’s recommended that you have students list the dive plan on their slates

– times, depths, turn pressures, etc., plus the skills, in order, to consult

during the dive. Get them in the habit of doing this for each dive.

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4. Dive and skill overview – describe how the overall dive will go,

detailing each skill, the performance requirements and how you’ll

conduct the dive, including signals you will use, etc.

a. controlled descent

b. bubble check and descent check

c. gas shutdown drill – 45 seconds (30 if not wearing isola-

tor doubles)

d. time/depth and gas supply awareness

e. turn pressure/time limit awareness

f. lift bag/DSMB deployment

g. ascent along lift bag line to simulated decompression

stop

h. simulated decompression stop while neutrally buoyant

n. simulated emergencies



a. Predive check – should be check each other using the

DSAT TecRec Dive Planning Checklist slates – technical

level BWRAF included.

b. It’s recommended that you spot

check everyone’s gear after it is

donned.

c. Per team, no one is ready until

everyone is ready.

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III. Tec 40 Training Dive Three – suggested sequenceA. Entry – appropriate for local environment.

1. Divers check their weight (if necessary, without deco cylinders)

2. Don deco cylinder at the surface.

3. Bubble check at surface (may be combined with descent check if sur-

face conditions are somewhat choppy).

B. Descent

1. Students descend using buoyancy to maintain a controlled rate

along a line, staying in teams and maintaining team contact.


C. Dive skills – there are no new skills on this dive. Students should perform

skills related to normal dive conduct (bubble checks, ascent checks etc.) with-

out prompting. Other skills (e.g. gas shutdown drills) they perform on signal

as briefed.

1. Bubble check (if not performed at surface) and descent check Before

dive, quietly assign one or two students to have minor “problems”

(e.g. loose crotch strap,) for team mates to catch – if possible, choose

a different student and problem from Dive Two.

2. Gas shutdown drill – 45 seconds (30 if not wearing isolator)

3. Time/depth and gas supply awareness – on a slate, divers should

record their cylinder bar/psi at each 10 minutes of dive time for entire

dive, amid other skills as necessary. Team mates may remind and

assist each other.

4. Turn pressure/time limit awareness –students signal you and their

team mates when they reach the turn pressure or dive time based on

the simulated decompression dive they calculated.

Note: Remind students that because this is a no stop dive, the dive

will continue until reaching the no decompression or gas sup-

ply limits [reinforce planned actual dive time/gas supply lim-

its.

5 Lift bag/DSMB deployment – on your signal one diver from each

team deploys lift bag/DSMB to surface.

a. Teams should decide who this will be during dive planning.

b. If there is a diver in each team who did not send up a lift bag/

DSMB in Tec 40 Training Dive Two, that diver should deploy

the bag.

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6. Ascent to simulated decompression stop – divers ascend along the

lift bag line at 10 metres/30 feet per minute (or slower if indicated by

their computers) to the first scheduled decompression stop.

7. Simulated decompression – students remain as a team under the lift

bag/DSMB and complete simulated decompression per schedules.

a. Divers should use buoyancy control to maintain stop depth.

This may be a drift decompression.

b. Remind students that they should remain within approximate-

ly .5 metres/1.5 feet of stop depth.

c. Remind students to maintain a roughly horizontal position

with their chest at stop depth.

d. Divers with decompression cylinders (recommended) may NO

TOX switch to the cylinders at the first stop. [Note: At this

level, divers will still be gaining skill doing this neutrally

buoyant. Have team mates do this one at a time and assist

each other with depth control. You may allow more latitude

for depth variance during the switch.]

12. Simulated emergencies – tell students that depending upon time, gas

supplies, etc, throughout the dive you may surprise them with

impromptu emergencies via hand signals or your slate that they must

respond to appropriately.

Note: Simulate situations students should already be prepared to

deal with based on their training to this point.

D. Surface and exit – technique suited to environment. Students wearing deco

cylinders remove them in the water.

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IV. Post DiveA. Performance review. After a moment to rest, get a drink, etc., but immediate-

ly while all memories are fresh, have teams identify what happened, mis-

takes, what worked, what didn’t, what they learned, etc. Comment and fill in

missing information as necessary, but have students critique themselves con-

structively while you guide the process.

Note: The next dive is an actual decompression dive. Students must have met all per-

formance requirements and demonstrated their ability to conduct such a dive before

moving on to it. If you or a student has any doubts about this, repeat Tec 40 Training

Dive Three and/or provide any necessary remediation before continuing on to Tec 40

Training Dive Four.

B. Confirm that all divers recorded their pressure information at each 10 min-

utes.



E. Remind students of assignments/tasks before next scheduled meeting (knowl-

edge development, etc.)

Tec 40 Training Dive fourTo successfully complete this training dive, the student must be able to:

1. Working in a team, 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 pro-

cedure.

2. Complete an actual decompression dive within Tec 40 limits (40 metres/130 feet max

depth, 10 minutes max deco, EANx50 max oxygen content).

3. Descend along a line to the bottom, maintaining control of depth and descent speed by

adjusting buoyancy.


5. As part of a team, demonstrate time/depth and gas supply awareness and turn pressure

and time limit awareness by turning the dive at the planned time, when any team mate’s

computer shows the planned decompression time or when any team mate reaches turn pres-

sure.

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6. Ascend at a safe rate not to exceed 10 metres/30 feet per minute, or slower if prompted by

a dive computer, and complete the required decompression as a team.

7. Throughout the dive, respond appropriately to actual or simulated problems or emergen-

cies.

Reminder: As you know, beginning with Training Dive One, students must demon-

strate mastery of all skills in each training dive prior to progressing to the next.

Because Dive Four is the first actual decompression dive at this level, there should be

no doubt that skills learned and practiced in the previous dives have been mastered.

Remember, you do not continue instruction into Training Dive Four with any students

who have not yet demonstrated mastery of all prior skills and learning.

I. Training Dive StandardsA. Tec 40 Training Dive Four is conducted in open water. (See Section Two,

Course Standards for definitions of these.) The minimum depth is 26

metres/85 feet and the maximum depth is 40 metres/130 feet. It is a

decompression dive within Tec 40 limits: max 40 metres/130 feet, max 10

minutes decompression, max EANx oxygen content 50 percent.

1. Students will make an actual dive requiring decompression within Tec

40 limits.

B. Ratios – 3 students to 1 instructor, with 1 more students permitted with

a certified assistant to a maximum of 4. (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

characteristics and environmental/logistical variables.


Knowledge Development One (Tec 40 kit, standardized technical rig or

sidemount) with accommodation for environmental needs. This includes

a decompression cylinder. It is recommended that each student have an

individual cylinder, but acceptable for students to share cylinders.

1. The instructor may wear the standardized technical rig.

D. Gas requirements: Students and staff may use air or enriched air, any suit-

able blend up to EANx50 or that reaches 1.4 at the maximum planned depth,

whichever is less, in sufficient supply to accomplish the dive and maintain

the planned reserve (thirds or more).

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1. It may be helpful to use a relatively “thin” EANx for bottom gas, or air,

to take students past no decompression limits for a genuine decompres-

sion training dive.

2. It is recommended that students have decompression cylinders with a

higher oxygen EANx blend. This provides extra gas, and helps make

their decompression extra conservative. If using a blend that is not

breathable at the maximum depth, remind students of this. Also

remind them to NO TOX switch at the first stop.


A. Predive briefing

1. Students set up their rigs, but do not don exposure suits yet


labels, etc.




a. Depth, temperature, entry/exit points, note worthy features, etc.

b. Facilities – overview parking, lockers, boat dry and wet areas,

where to find emergency equipment, etc.

B. Dive overview

1. It is recommended that you schedule Tec 40 Practical Application Three

before this dive and integrate the dive planning and preparation for the

dive with the dive planning assignments in the practical application.

2. Depth/time limits – students plan for depth, time and decompression

and limits you provide.

a. Students should to have the decompression schedule (written on

a slate or printed and laminated tables) to follow in the event of

a computer failure and/or for reference in an omitted decompres-

sion situation.

3. It’s recommended that you have students also list the dive plan on their

slates – times, depths, turn pressures, etc., to consult during the dive.

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4. Dive and skill overview – describe how the overall dive will go.

Explain that the point of this dive is to put into practice everything

they have learned and practiced.

a. controlled descent

b. bubble check and descent check

c. mission

d. turn dive at pressure/time limit

e. ascent and decompression

f. simulated/actual problems and emergencies

5. Teams plan how to accomplish mission (optional)

a. If possible, assign a mission or task to team. Alternatively,

teams may plan their own.

b. The mission should be very simple, short and reasonable

for Tec 40 limits

c. Remind students that accomplishing the mission is not

required and the dive should end when the team reaches a

planned limit. The overriding mission of any dive is return-

ing safely.



a. Predive check – should be check each other using the

DSAT TecRec Dive Planning Checklist slates – technical

level BWRAF included.

b. It’s recommended that you spot check everyone’s gear after

it is donned.

c. Per team, no one is ready until everyone is ready.

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III. Tec 40 Training Dive four – suggested sequenceA. Entry – appropriate for local environment.

1. Divers check their weight (if necessary -- without deco cylinder)

2. Don deco cylinder at the surface.

3. Bubble check at surface (may be combined with descent check if sur-

face conditions are somewhat choppy).

B. Descent

1. Students descend using buoyancy to maintain a controlled rate along

a line, staying in teams and maintaining team contact.


C. Dive skills – there are no new skills on this dive. Students should perform skills

related to normal dive conduct (bubble checks, ascent checks etc.) without

prompting. Other skills (e.g. gas shutdown drills) they perform on signal as

briefed.

1. Bubble check (if not performed at surface) and descent check

2. Mission – optional, as planned, accomplishing it is not required

3. Turn dive at pressure/time limit awareness –students signal you and

their team mates upon reaching any dive limit

4. Ascent and decompression– divers ascend and complete the required

decompression

a. You may have students ascend along a lift bag/DSMB line (if so,

have teams plan time for deploying it), mooring or anchor line, or

other appropriate ascent method.

b. Divers NO TOX switch to deco cylinders (if carried) at first stop.

c. Remind students that they should remain within approximately .5

metres/1.5 feet of stop depth and maintain a roughly horizontal

position with their chest at stop depth.

12. Simulated and actual problems and emergencies – tell students that

you may simulate minor problems or emergencies for them to handle,

but none of these would waste gas (e.g. free flowing regulator) or cause

them to abort the dive. Any problems of that nature are genuine.

D. Surface and exit – technique suited to environment. Students wearing deco cyl-

inders remove them in the water.

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IV. Post DiveA. Performance review. After a moment to rest, get a drink, etc., but

immediately while all memories are fresh, have teams identify

what happened, mistakes, what worked, what didn’t, what they

learned, etc. Comment and fill in missing information as necessary,

but have students critique themselves constructively while you

guide the process.

B. Divers disassemble and stow equipment.


E. Remind students progressing immediately into the Tec 45 course

of assignments/tasks before next scheduled meeting (knowledge

development, etc.)

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Tec40

Sports

Transcript of Tec40