Tec45

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Instructor Guide Section fIve: Tec45

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five: Tec 45 Standards and Course Content

The Tec 45 subcourse of the DSAT Tec Diver course introduces Tec 40 divers to the first stages of full, technical deep decompression diving. Certified Tec 45 divers are qualified to make multistop decompression dives that employ EANx and oxygen for accelerated decompression.

The expectation is that a Tec 45 diver intends to continue on in technical diving. Accordingly, the course not only develops the knowledge and skills to make open circuit technical dives as deep as 45 metres/145 feet, but also begins developing the knowledge and skills the diver will need at the Tec 50 level and beyond.

Program SequenceThe Tec 45 course consists of three knowledge development sections, three practical appli-

cations sessions and four training dives. You will find these in the Knowledge Development, Practical Application and Training Dive subsections, each with content/presentation outlines and related standards.

The fully integrated instructional sequence for the Tec 45 course is:Tec 45 Knowledge Development OneTec 45 Practical Application OneTec 45 Training Dive OneTec 45 Knowledge Development TwoTec 45 Practical Application TwoTec 45 Training Dive TwoTec 45 Knowledge Development ThreeTec 45 Practical Application ThreeTec 45 ExamTec 45 Training Dive ThreeTec 45 Training Dive Four

The Tec 45 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:

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Section fIve: Tec45 Instructor Guide

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• Any knowledge development sections, practical applications or training dives that precede a training dive in the integrated sequence must be successfully completed before that training dive.

• Any knowledge development sections or practical applications that precede a practical application in the integrated sequence must be successfully complet-ed before that practical application.

• Any knowledge development section that precedes another knowledge devel-opment section must be successfully completed before that knowledge devel-opment section.

For example, the following sequences would be acceptable:Tec 45 Knowledge Development OneTec 45 Knowledge Development TwoTec 45 Practical Application OneTec 45 Practical Application TwoTec 45 Training Dive OneTec 45 Training Dive TwoTec 45 Knowledge Development ThreeTec 45 Practical Application ThreeTec 45 ExamTec 45 Training Dive ThreeTec 45 Training Dive Four

Tec 45 Knowledge Development OneTec 45 Knowledge Development TwoTec 45 Knowledge Development ThreeTec 45 Practical Application OneTec 45 Training Dive OneTec 45 Practical Application TwoTec 45 Training Dive TwoTec 45 ExamTec 45 Practical Application ThreeTec 45 Training Dive ThreeTec 45 Training Dive Four

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Tec 45 Key Standards Participant prerequisites:

• Certified as a Tec 40 diver or qualifying certification from another training organization. For the purposes of this level, a qualifying technical certification is one that qualifies the student to make decompression dives to 40 metres/130 feet using air and EANx using open circuit scuba equipment. 18 years old, 50 logged dives (12 deeper than 18 metres/60 feet using EANx, at least 6 deeper than 30 metres/100 feet (with or without EANx).

• Instructor qualification: Teaching status, insured (where required) Tec Deep Instructor• Assistant qualification: renewed, insured (where required) PADI Divemaster or higher

certified as a Tec 45 or higher level TecRec diver

Training Dive One Environment: Confined water or limited open water with ready access to water shallow enough in which to stand. Depths: Minimum: 2.4 metres/8 feet Maximum 10 metres/30 feet Decompression: No stop only Gases: Air or EANx, recommended that all blends be breathable at maximum dive depth Ratios: 6:1, 8:1 with one or more certified assistants

Training Dive Two Environment: Open water Depths: Minimum: 12 metres/40 feet Maximum: 18 metres/60 feet Decompression: No stop only Gases: Air or EANx, recommended that all blends be breathable to maximum dive depth Ratios: 4:1, 6:1 with one or more certified assistants

Training Dive Three Environment: Open Water Depths: Minimum: 18 metres/60 feet Maximum: 30 metres/100 feet Decompression: No stop only Gases: Air, Air, EANx or oxygen Ratios: 4:1, 6:1 with one or more certified assistants

Training Dive four Environment: Open Water Depths: Minimum: 27 metres/90 feet Maximum: 45 metres/145 feet Decompression: Single gas decompression, gas switch for conservatism, Gases: Air, EANx or oxygen Ratios: 3:1, 4:1 with one or more certified assistants

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Tec 45 Knowledge Development

Knowledge PreassessmentThe Tec 45 course builds upon and extends the knowledge development estab-

lished in the Tec 40 course. A lack of understanding or familiarity with the fundamental knowledge required of a Tec 40 diver can substantially impede learning at the Tec 45 level, and in some cases, raise safety concerns. Therefore, it is important to verify and assess prerequisite knowledge before beginning Tec 45 level knowledge development. Apply these standards:

1. Students who enter the course with a qualifying prerequisite certification (not DSAT Tec 40 certification) must complete all the Tec 40 Knowledge Reviews and the Tec 40 Exam. It is recommended that you have these students complete the reading assignments first. Check over the Knowledge Reviews and score the exam, pro-viding remediation to achieve mastery as necessary.

2. Students who enter the course as DSAT Tec 40 divers (not a qualifying certification from another organization) who you did not personally certify, and/or who completed certification more than six months prior to the start of the course, must retake the Tec 40 exam. Score the exam, providing remediation to achieve mas-tery as necessary.

3. As appropriate, it’s recommended that you preassess potential students’ skill and knowledge in a confined water session and/or interviews. You can combine remedi-ation with preassessment, refreshing student capabilities to mastery prior to beginning the course.

4. Students who you certified as DSAT Tec 40 divers (not a qualifying certifica-tion from another organization) within six months of starting the course do not have any particular assessment requirements. It is recommended that you check their training records for any areas that may have had difficulty and conduct informal assessments by asking questions, etc.

The following knowledge development outlines provide the course content in presentation form. If the Tec Deep Diver Manual is not available in a language the stu-dent understands, you may use the outline to present all course content. Otherwise, it is recommended that you cover knowledge development through student independent study with the manual and handouts, with presentations that review/remediate what they studied.

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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 convenience) 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 independently 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 45 students do not use the Knowledge Reviews in the Tec Deep Diver Manual. Instead, copy the blank Tec 45 Knowledge Reviews in the Appendix of this guide for their use. You will also find the answer keys there. Students have not completed a Knowledge Development until they have completed the corresponding Knowledge Review cor-rectly, accurately and completely.

The final step in completing Tec 45 Knowledge Development is the Tec 45 Exam. Tec 45 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 mastery 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 45 Practical Application Three.

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

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Tec 45 Knowledge Development One[The voice in these presentations addresses students. Notes to the instructor appear in brackets.]

I. Introductory SessionLearning ObjectivesBy the end of this section, you should be able to answer these questions:1. What are the goals of the Tec 45 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 students become acquainted.]

2. [Have students introduce themselves and tell something about themselves, diving interests, etc.]

3. [Collect and review Tec 45 Knowledge Review One].a. [Review the answers to assess mastery so you can tailor your presen-

tations accordingly.]B. Course Goals

1. The goals of the Tec 45 course area. To qualify you to make limited decompression dives using air,

enriched air and oxygen to a depth of 45 metres/145 feet or less.• Certification as a Tec 45 diver qualifies you to use a single

decompression gas of up to 100 percent oxygen to make your decompression more conservative or to accelerate your decompression.

b. To train you in the knowledge, procedures and motor skills required for decompression diving within the limitations of the Tec 45 certifi-cation.

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 45 limits.

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e. To lay the foundation continuing your training in the Tec 50, Tec Trimix 65 and Tec Trimix Diver courses.

C. Your Obligations and Responsibilities1. During the Tec 45 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 to 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 quali-fied 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 conse-quences: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. Administrationa. Course costs [Explain and collect, as appropriate, all costs associated

with the course, refund policies, etc.]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.

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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.]

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 training.]

f. [Have student divers read, complete and sign the PADI Medical Statement. Prior to Tec 45 Training Dive One, 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. [Diver insurance – It’s recommended that you require students in the DSAT Tec 45 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 handle knowledge development.]a. You will study independently with the Tec Deep Diver Manual

and provided handouts.• The manual supports the entire Tec Diver course as well

– Tec 40 through Tec 50. You should have already read much of it.

• Read the assigned handouts, sections and exercises.b. You will use the manual to complete knowledge reviews provid-

ed to you. Do not use the knowledge reviews in the manual.c. We will review the material and help with anything you don’t

understand [state where/when: class sessions, practical applica-tions, predive sessions, etc.]

d. You will complete the Tec 45 Exam before the last two training dives of the course.

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II. equipment[Note to instructor: Students who took the Tec 40 course in the standardized techni-cal rig (or sidemount) will have already completed this section. At your discretion, they do not have to repeat it. Students who took the Tec 40 course using the basic Tec 40 configuration do need to complete this section.]

Manual Supported ContentStudy assignment: Tec Deep Diver Manual, pgs 10-33, Equipment I, Tec Exercise 1.2, pgs 80-87, Equipment II, Tec Exercise 2.1, pgs 142-145, Equipment III, Tec Exercise 3.1Watch the TecRec Equipment Setup and Key Skills video.

Learning ObjectivesBy the end of this section, you should be able to answer these questions:1. What is meant by “standardized technical rig,” and why do technical divers need to apply it?2. What guidelines apply to selecting masks, fins and snorkels for technical diving?3. What characteristics should you look for in a cylinder valve or manifold used for deep technical diving?4. What is the minimum number of fully independent regulators, per diver, and how do you configure each?5. What three characteristics should you look for in a BCD, and what five character-istics should you look for in a harness, for a deep technical diving rig?6. How do you choose an appropriate exposure suit for a deep technical dive, and how may your choice affect your BCD choice?7. What are your options regarding a weight system, and what are the advantages and disadvantages of each?8. What instrumentation do technical divers generally carry, and why do they gener-ally avoid consoles?9. What are the three types of computers you can use for technical deep diving with air and enriched air, and what are the advantages and disadvantages of each?10. What types of cutting tools are appropriate for deep technical diving, and at least how many should you have with you? 11. What are six general guidelines regarding pockets, accessories and clips you might need when technical diving?12. What is the difference between a stage bottle and a decompression cylinder?13. How do you set up a stage/deco cylinder?

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14. What is the advantage of a stage/deco cylinder connection you can cut?15. Why would you need a lift bag/DSMB and reel?16. What are suitable lift bags/DSMBs and reels, and where do you secure them on your rig?17. What makes a suitable spare mask for tec diving?18. What are the issues and recommendations relating to equipment and oxygen compatibility?19. What are four recommendations regarding equipment maintenance?20. What are three reasons that technical divers consider a slate standard equip-ment?21. What is a “jon line,” and how do you use it?22. What benefits does a multigas computer offer you?23. What are the options regarding urination for long technical dives?

You should also be able to:17. Describe the layout, arrangement and configuration of the basic rig and equip-ment, head to toe, as worn for a technical deep dive.

A. The technical community has evolved a standardized technical rig that mini-mizes and streamlines your gear so that nothing dangles, everything is easily accessible and so you eliminate the unnecessary.1. With the extensive equipment needs in technical diving, you must

apply the standardized rig philosophy to minimize confusion and pro-cedural error due to equipment task loading, and to assure streamlin-ing, which avoids entanglements and reduces wasted energy due to drag.

2. Gear rigging may vary with the type of technical diving and still be consistent with the standardized technical rig philosophy. In this course, you’ll learn the basic technical diving setup most widely accepted in the technical diving community.

B. Mask, fins and snorkel.1. Choose a compact mask to maximize streamlining and to minimize

having it jostled loose by current.

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2. Choose fins with sufficient blade area and flex for power. Fins suitable for snorkeling or warm water recreational diving may not be suitable for tech-nical diving.

3. Usually you omit the snorkel. They are appropriate standard equipment for recreational diving, but not for tec diving. In tec diving condictions, a snorkel tends to create drag and be an entanglement hazard. a. In rare instances with long swims at the surface in conditions call-

ing for a snorkel (before or after a dive), you may choose a snorkel you can detach and stow for the dive.

4. Full face masks are not widely used for open circuit tec diving. However, at least one company manufacturers a model with interchangeable mouth “pods” that permit the diver to easily change gases and use standard sec-ond stages. The use of such a mask may be especially beneficial during decompression with oxygen, because it may reduce drowning risk in the event of a convulsion.

C. Cylinders and valves.1. The basic technical rig usually consists of twin cylinders chosen based on

your gas consumption, size and the dive requirements.a. Twin 11-12 litres/71.2-80 cubic foot cylinders are sufficient for

many divers going no deeper than 50 metres/165 feet.b. In some instances, a single 18-20 litre/105-120 cubic foot cylinder

with an appropriate valve will suffice for the planned dive.2. For twins, choose a valve with twin regulator posts that can shut down gas

to either regulator and still allow the other access to all gas in both cylin-ders (in case of a freeflow malfunction).a. You also want an isolator manifold, which has a valve that sepa-

rates the cylinders and saves half the remaining gas in the event of a manifold leak.

b. The DIN (Deutche Industrie Norm) system is preferred over the yoke system – considered more reliable because of the threaded connection and captured o-ring (some valves will accept either with an insert adapter.)

c. If you train in sidemount, you will have independent twin cylin-ders, and (obviously) no isolator valve. Your instructor will go over sidemount equipment specifics in detail.

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3. For a single cylinder set up, choose an “H” or “Y” valve, which have twin regulator posts and can shut down gas to either regulator and still allow the other access to all the remaining gas (again, the DIN system is preferred).a. All your training in the Tec 45 course will be in doubles, but you

may elect to use a single at times as a certified Tec 45 diver.4. Cylinder and valve accessories

a. A remote-close cable for the isolator manifold is common in a few areas with specialized needs, such as in cold water where thick exposure suits make it difficult to reach the valve.

b. Some wreck divers use valve guards to protect against impact inside wrecks; the trend is away from these due to bulk and entanglement, though they’re common in some environments that call for them.

5. Doubles are set up with doubles bands set with the mounting bolts a standardized 28 cm/11 inches apart. Setting up doubles takes some training and practice, so have your PADI Dive Center or Resort handle it for you.a. Sidemount cylinders ride on either side of your body much like

stage/deco cylinders. These don’t require a manifold, but they do require special clips and other rigging as well as a specialized harness.

D. Regulators1. In deep technical diving, the minimum is two fully independent regula-

tors per diver (this does not include those used on stage or decompres-sion cylinders).

2. Choose top of the line balanced regulators for maximum reliability and performance at depth.

3. Configure the right post (as worn) regulator with a low pressure inflator hose and the second stage on a 1.8 m/7 ft hose. Sidemount will be simi-lar, though you will have an SPG. Its hose and the low pressure inflator hose lengths may differ.

4. Configure the left post regulator with the SPG and the second stage on a standard length (about 80 cm/32 in) hose.

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5. The left regulator may or may not have a low pressure inflator hose (more about this later).

6. Note: neither regulator needs an extra second stage (one per regulator).7. Again, the DIN system is preferred (most DIN regulators accept adapters

for yoke system use).8. Sidemount configuration is similar – your instructor will show you the

sidemount configuration if you’re completing the course in sidemount.E. BCD and harness

1. The basic deep technical rig calls for a harness that sits on top of an inter-changeable BCD bladder; this attaches to double cylinders via recessed wing nuts that screw down on the band bolts.a. In the case of sidemount, the BCD bladder may or may not be

incorporated into a typically fabric harness. There are no bands to mount to with sidemount, however, the harness may have a metal rail system at the bottom and back of the harness, which is used to connect the lower part of cylinders.

2. BCDs –called “wings” (because they let you “fly” doubles or because they resemble stubby wings). a. Size – a wide variety is available; choose based on adequate lift to

hold you at the surface wearing all the gear for the planned dive, and with all cylinders full.

b. Single bladder (has a single air cell, inflator and deflator) and double bladder (two air cells, inflators and deflators) models are available.

c. You need back up buoyancy if your primary BCD fails. Options depend upon your other gear:• Single bladder: when using lighter cylinders with a dry suit• Double (dual bladder): needed for heavy cylinders with a

dry suit, or diving a wet suit, so you can still restore posi-tive buoyancy even with a major BCD failure. The heaviest diving rigs may pose too much weight for dry suit back up buoyancy; you may need a double BCD in either a wet or dry suit. This is the generally preferred choice.

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• Unrestrained or “bungeed” BCDs – Bungeed wings have elastic or tubing that constricts the BCD to minimize pro-trusion and reduce the profile for wreck penetration div-ing.o bungeed wings should not be so tight that they

would squeeze out all air if you had an exhaust valve failure or hole

o some BCD wings have adjustable elastic that you set for the required buoyancy; this will not squeeze out all air; some allow you to release the bungee during the dive

3. Harness – holds the BCD to the cylinders, and the assembly on to you.a. Style – Plate (steel, aluminum or plastic) with standard nylon

webbing is simple and holds a lot of weight securely. A soft har-ness is all standard nylon webbing and fabric; it is a bit more ver-satile and comfortable, but not as simple. It also weighs less, which is advantageous for traveling divers.

b. Crotch strap – Due to the bulk and buoyancy distribution, you’ll need a crotch strap with most harnesses.

c. Shoulder harness adjustable quick release connectors – they are generally not needed, but are convenient. Should you need assis-tance, they simplify getting you out of your gear; without them, they may have to cut your straps to get you out of your rig.

d. Adjustable D-rings at the shoulders (two max each side) on straps, standoff (bent out or rigid), are recommended. Custom BCD with “permanently adjusted” D-rings are an option. Rigid D rings on the waist strap at hips (one each side) are essential – you need them located for optimum stage/decompression cylinder car-rying (more about this later in the course).• Fabric “butt plates” can be added to some BCDs.

Developed for sidemount, these plates have cylinder attachment rails that some backmount divers prefer for stage/decompression cylinders in place of hip D rings.

• Sidemount harnesses will also have two bungees clipped off to the back of the harness and to the front shoulder D-rings. This bungee is placed around the valve of each

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cylinder to hold it close to the diver’s body. These should be attached underwater and not used to support the weight of the cylinder out of the water, because the bungee isn’t strong enough. Many divers will use a short loop of nylon cord with a bolt snap that can be easily be looped around the valve out of the water to support the cylinder and allow the diver to enter and exit with them on, if needed.

• If using a quick release on the harness shoulder, D-rings should be above the release – this makes adjustment easier, and the stage bottle keeps the rig on you if you release it accidentally (very rare with modern harnesses).

e. Waist strap – is usually a standard webbing/buckle on a plate har-ness, or a standard webbing/buckle with a removable “cummer-bund,” foundon many soft harnesses. Avoid harnesses with cum-merbund only (these are not as strong and create gear positioning problems). Many divers prefer a metal buckle to avoid breakage when moving heavy gear.

4. The BCD may or may not be partly integrated to your harness; you will want to choose your BCD and harness as a system.

5. Many avid technical divers have two or three wings, or entirely separate BCDs and harnesses, to match differing dive requirements.

F. Exposure suits1. As in recreational diving, you choose your exposure suit based on the

water temperature at depth and the dive duration.a. Exposure protection suitable for short recreational dives may not

be sufficient for long technical dives.b. You almost always need more insulation for a technical dive due to

duration and decompression/safety stops without much exertion.2. Dry suits

a. For longest durations/coldest water.b. May permit using a single bladder BCD.c. Inflate with argon system for additional insulation.d. Master dry suit use in recreational diving before using one in tech-

nical diving. At least 20 dives is a conservative minimum before using your dry suit for tec diving. The PADI Dry Suit Diver course recommended.

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• Note that in recreational diving, you use only the dry suit for buoyancy control underwater.

• In a heavy weight technical rig, you may need to use both the suit and your BCD – a more complex skill to master.

3. Wet suitsa. For most divers, a full 6 mm 1/4 in. wet suit with hood will suf-

fice in water 24°C/75°F or warmer for two to three hour dives. Choose high quality neoprene to withstand the rigors of com-pression and recovery inherent to deep diving.

b. Choose a redundant (double bladder) wing BCD, because drop-ping weights (if any) may not give you sufficient buoyancy if your BCD fails, or dropping weights may make you too buoyant to make your decompression stops.

c. Note that at depth, wet suit compression may require substantial air in the BCD.

d. The advantage of diving in a wet suit is simplicity – you only need to adjust the BCD. A minor tear will not substantially affect your thermal protection.

G. Weight systems1. With aluminum double cylinders, you will probably still need weights.

With a heavy weight rig, you may not.2. The choices are weight belt, integrated weight system and weight har-

ness.a. Weight belt

• Advantages: simple, readily available when needed.• Disadvantages: must don after putting on rig so it’s not

trapped by crotch strap; can be hard to position securely amid other components. Note: Since losing weights on a deco dive can be hazardous (discussed in a moment), some divers intentionally wear their crotch straps over their weight belts, knowing they’ll have to release it in a weight ditching emergency.

b. Integrated weight system• Advantages: no need to put on last; prepositioned amid

rest of rig

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• Disadvantages: must have a harness system that accepts one; makes an already heavy rig heavier; may add clutter to the configuration (depends on design)

c. Weight harness• Advantages: it is put on before the rig; does not add to rig’s

weight; provides key advantages of both weight belt and weight system

• Disadvantages: may be awkward to adjust and position so that rig doesn’t interfere with weight ditching; may interfere somewhat with putting rig on

d. Combination• Advantages: loss of one weight system doesn’t lose all your

weight; may make configuration and donning easier.• Disadvantages: more complicated preparation, one more thing

to remember.

3. Loss of weights can be a significant hazard when wearing lightweight rigs (such as twin aluminums), due to out of control ascent and the inability to make required decompression stops.a. Some tec divers use double buckles on weight belts to prevent acci-

dental release.b. Another technique for backmounts is to use a metal plate and thread

smaller weights into the harness in the shoulder area. Typical plates weigh 2.7 kg/6 lbs. Adding small weights to the harness can provide the diver up to 3.5 – 4.5 kg / 8 – 10 lbs that can’t be accidentally lost. While this may not provide sufficient weight alone, it makes loss of weight less of an issue with the remaining system.

c. A third backmount technique is the use of a keel weight. This is a bar weight that fits between the cylinders, generally under the harness.

H. Instrumentation1. Basic deep technical rig instrumentation: SPG, compass, computer or timer/

depth gauge and back up computer or timer/ depth gauge.2. Technical divers generally prefer arm-mount instruments (generally SPG is

not arm-mounted, though it can be) – consoles are bulky and protrude (doesn’t follow the standardized technical rig philosophy) creating drag and

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entanglement hazard. (Note: you can often mount two gauges on a single wrist strap. Some tec divers carry back up instruments clipped inside a pouch or pocket.)

3. SPG (submersible pressure gauge)a. One only (except in sidemount) – there is no back up (it cre-

ates two potential high pressure leaks); failure means end the dive immediately

b. Mechanical preferred – reliable with no battery concernsc. In sidemount, smaller and lower profile preferred

4. Compass -- Good quality, liquid filled as used in recreational diving. It is commonly carried in a pouch until needed, rather than worn.

5. Timer and depth gauge (integrated or separate)a. May be used in place of computer when diving with tables

(though most common “timer-depth gauge” is a dive computer set to gauge mode.)

b. May be used to back up a computer (with tables).6. Dive computers

a. State of art in tec diving is the multiple gas computer.b. Modern computers accept as many as 7 different gases that

you can switch to “on the fly” (during the dive) to accelerate decompression. Some allow you to add or delete gas blends underwater to handle emergency situations.

c. Many also calculate helium dives – useful for diving trimixd. Single gas computers can be used, but at this level, are typical-

ly used as timer/depth gauges along with tablesI. Cutting tools

1. You always dive with at least two cutting tools.2. Carry at least one where you can deploy it with either hand.3. Common types and locations include:

a. Typical dive knife – sharp and in excellent condition; com-monly worn on inside of calf (on the outside is prone to entan-glement and hard to reach with either hand), however, most tec divers have moved away from large, leg knives altogether.

b. Small dive knife – sharp, typically worn in sheath near center of waist band.

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c. Z-knife – a small hook with blade especially suited to cutting fine line. It is worn on a gauge strap, harness or BCD deflation hose.

d. EMT shears – heavy duty shears that cut rope (some will even handle cable). These may be worn on the calf, harness or waist.

e. Bosun’s knife or other folding knife – very sharp for cutting line, often carried with clip or lanyard in a pocket or under instrument wrist bands

f. Multi tools – Leatherman®- type tools, sometimes carried to meet specific dive objectives, usually in a sheath/pouch on the waist band or in a pocket with a clip.

4. Different types of technical diving have different cutting tool concerns (e.g., cave divers never wear large, calf-mounted knives).

J. Guidelines for pockets, clips and accessories1. To minimize confusion and bulk, avoid large pocket pouches on the har-

ness; small pockets for back up gear (e.g., spare mask) that are out of the way at the hips are okay.

2. The most useful pocket in tec diving is on the outside of the thigh on the exposure suit (some manufacturers make a strap-on pocket if your expo-sure suit doesn’t have one). Some sidemount divers prefer it on the front of the thigh so they can reach it by lifting a knee.

3. Use brass or stainless steel clips on accessories, SPG, etc. Mount clips on accessories, not on the BCD.

4. Sliding gate clips (a.k.a. “dog clips”) are preferred by most divers to marine snaps (a.k.a. “swinging gate clips”), because they won’t acciden-tally snap on to things by themselves.• Choose clips for the environment– smaller clips that work easily

in warm water with thin gloves may be impossible to use in cool water with thick gloves.

• You should be able to reach all clips, because all clips can entangle or need your attention.

5. Accessories on a D-ring should be well out of way when stowed, and not dangle or create entanglement potential. If possible, keep accessories in a pocket except when in use, and clip them off only to free hands momen-tarily or to avoid dropping them while using them. If possible, only hang one item per D-ring.

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6. Use a breakaway clip on anything you may need to discard or release in an emergency. A simple breakaway: connect a clip to accessory or gauge via a small o-ring or small, thin cable tie. In an emergency, a sharp pull or twist breaks the o-ring/cable tie, releasing the accessory or gauge.

K. Basic rig: head-to-toe configuration– how everything fits together. [Note to instructor: The most effective way to demonstrate this is to have a

staff member wearing the kit for you to demonstrate.]1. Regulators and valves

a. Short hose regulator on the left post - The SPG goes straight down, the gauge mounts at the left hip D-ring or on chest on an upper left or right D-ring with a break away clip. The second stage goes to the right and then rests on the upper chest held by a bungee or surgical tubing “necklace.” The LP hose goes to the right to the back up BCD inflator (if used), or straight down and in, to the dry suit inflator. If using an argon system and no back up BCD, there is no LP inflator hose. For sidemount, the left regulator is the same, however, the SPG may be on a short hose. It rests on the shoulder of the cylinder or in some cases may route directly out from the first stage to make it easier to see. The LPI hose for the BCD connects directly to the BCD, but will have a small loop that folds up underneath the diver’s arm.

b. Long hose regulator on the right post- The LP inflator hose goes from it to the BCD inflator. The second stage hose goes straight down behind the BCD wing, up at the hip, across the chest (held in place by a rigid D ring and the safety reel), behind the neck from the left and around into the mouth. A break away clip is mounted where the hose meets the second stage (not clipped while in use). The reel is normally clipped on the right hip D-ring to hold the hose in place. For sidemount, the long hose routes down along the right cylinder, up around the diver’s neck and into the mouth. The hose is held by a bungee or shock cord around the cylinder. A break away clip is mounted in same loca-tion as on a back mount. Reels are typically clipped to a D-ring located on the back of the harness/BCD.

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c. Note that all hoses route in or down – never out (except a short hose SPG in sidemount).

d. All valves and the isolator are all the way open. Do NOT close back a partial turn. This assures they only turn one direction in a shut-down emergency – closed.

2. BCD and harnessa. The primary BCD inflator hose is over left shoulder, retained so it

won’t float away.b. The back up BCD inflator is clipped behind the wing or bungeed to

the cylinder on the left or right (depends upon how the BCD is laid out) to avoid confusion with the primary. (Note: You never use both BCDs at the same time.) If using a high flow inflator, many divers bungee the low pressure hose in place, but don’t connect it so as to avoid a runaway ascent if the back up low pressure inflator malfunc-tions. In a BCD failure situation, they would use oral inflation if they need to quickly establish buoyancy, then connect the LP hose after stabilizing the situation. Note that sidemount configuration generally requires a specialized bladder or rigging.

c. If using a dry suit, you should ideally be able to hold the BCD infla-tor and press the dry suit inflator with the left hand at the same time.

d. Pockets (if used) should be small and mounted at the hips, out of the way. (The ideal place for a pocket is on the exposure suit thigh).

e. Straps are adjusted/trimmed so there’s no excessive slack dangling from any slide or buckle.

f. The height on cylinders is adjusted so you can reach both regulator valves and the isolator (with loosened waist/crotch strap acceptable).

3. Exposure suita. The argon system (if used) usually is mounted on the left cylinder or

side of the harness, inverted, regulator in, so you can open the valve while worn. The LP hose to the inflator is threaded under the har-ness, as necessary, to eliminate protruding slack. There is no second stage on the regulator. The system is mounted with straps you can cut away if necessary. Some divers prefer to wear it on the right.

b. Desirable accessories• Thigh pockets• Knee pads

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4. Instrumentsa. Arm mounted, either side preferred

• mounting all one side makes one arm “clean” for more eas-ily sliding in and out of harness

• some types of tec diving (e.g. scootering in a cave) make it important to mount gauges on one arm or the other

b. The compass is positioned on the arm so you can center it for accurate navigation (it is frequently stored in a pocket/pouch if use is not expected)

c. Two computers, or one computer and one depth gauge/ timer/tables, or two depth gauge/timers and tables.

5. Mask and finsa. No snorkel in most circumstancesb. Spare mask (optional) in an out-of-the-way harness pocket or in a

thigh pocketc. Fins are preadjusted and taped or otherwise secured so they can’t

slip or dangle (unless they have spring heel straps or are adjustable while being worn).

d. Inspect straps frequently – this is one of the most common, but most avoidable gear failure points.

6. Weight system -– weights secure, free and clear for ditching; back up buckle secured (if used)

7. Cutting tools – two, mounted appropriately for type, at least one retriev-able by either hand alone.

8. Some variations on the above rigging suggestions exist, but these are the most common approaches. Agree on any departures with team mates – standardized rigs speed up your reaction time.

L. Stage and decompression bottles (stage/deco cylinders)1. They are worn on the side under the arm, clipped at the waist and on the

chest, and are often removed and then later replaced during the course of the dive.

2. Although rigged the same, stage bottles are cylinders used to extend your range (working part of the dive), while decompression (deco) bottles are cylinders with enriched air (higher oxygen content than your bottom gas) or oxygen for decompression.

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a. In this program, you’ll learn about using stage cylinders for extended no decompression dives, and decompression cylinders for decom-pression dives.

b. Handling considerations are the same for either, so exercises and descriptions refer to “stage/deco” cylinders.

c. Leaving either type cylinder for later retrieval and use is called “stag-ing,” regardless of whether it is a deco or a stage bottle.

d. The terms are used somewhat interchangeably. This actually isn’t confusing in context in most circumstances.

3. Typical configuration [show setup cylinder]a. Nylon rope or strap approximately 46 cm/18 in (more or less to indi-

vidual needs), runs under the valve opening from the neck down to a band around the cylinder, with a clip at each end – serves as handling strap underwater, plus provides clips for hip and chest D-rings; you may adjust bottom clip (some divers prefer it under the valve knob)

b. Regulator is a second stage and SPG only – hoses tuck under inner tubing, bungee, surgical tubing or other retaining band stretched around cylinder

c. The second stage has a clip with a breakaway mount so you don’t pull it out unintentionally

d. A short hose SPG, bent up and pull tied to the first stage, is popular with some divers

e. Suitable cylinders are those that are nearly neutral for easy handling; those substantially negative are not a good choice• an optional exception is an oxygen cylinder for use at 6 m/20

ft, since the added weight may benefit you if you’re under weighted

f. Decompression cylinder second stages may have mouth guards/blocks

g. Properly set up, the stage/deco cylinder should be a compact package that you can handle easily with nothing dangling or dragging

4. Stage/deco bottle clips usually attach to the cylinder via a rope or nylon strap, especially in penetration diving, so you can cut away the cylinder in an

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emergency. You can’t cut connections that are entirely metal. (Some divers use double ended clips; it’s unlikely that both ends would jam at the same time).

5. Single stage/deco cylinders are worn under either arm, usually the left arm. Multiple cylinders may be worn all on the same side or distributed on either side.a. You will learn to use two cylinders in the Tec 50 course.b. If wearing a second cylinder on the right, be sure it does not trap your

long hose – the hose should be routed below a hip D-ring when you clip.

c. When scootering, you may choose to wear all cylinders on the left so you can aim the propeller wash under your right arm.

d. You can clip cylinders you’re done with by the upper clip to a hip D-ring to get them out of the way.

M. Lift bag/Delayed Surface Marker Buoy (DSMB) and reel1. When diving in open water, you may accidentally find yourself away from the

anchor line or planned ascent line or area.2. In this instance, you deploy a lift bag/DSMB on a line from your emergency

reel.a. This gives you a line to ascend along and to use to control your depth

and stops.b. It marks your location for the boat and support team.

3. A suitable bag or buoy is brightly colored (yellow is preferred – it provides the best visibility amid white caps and in dim light) with at least 45 kg/100 lbs lift. Write your name on it in big letters for surface support identification. [Show example bag] A bright, elongated DSMB is also ideal, because it pro-trudes high above the water.a. In some areas, divers carry two bags/DSMBs – one of a different color

to signal for assistance from surface support.b. Different teams and areas have differing protocols regarding bag/

DSMB colors and uses.4. A suitable reel is compact, with ample line to reach the surface. Some divers

use two reels in tandem in case one jams. [Show reels.]5. Lift bags are commonly carried rolled up and bungeed to doubles or on the

small of the back. Compact DSMBs may fit in a pocket or be clipped with the reel. [Show stowed bag/DSMB on rig.]

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6. The reel clips to the right hip D ring to help hold the long hose in place. In sidemount, it clips to the back rail or a D ring behind the harness.

7. Lift bags/DSMB and reels are considered mandatory safety equipment in most areas. In some places, ascents with bags/DSMBs are standard operating proce-dures. In others, they are emergency procedures only. You’ll practice such ascents several times in this course.

N. Spare mask1. You have a big problem if you cannot read your tables or computer during a

decompression dive, because you can’t tell when to ascend to the next stop, and you can’t surface. Therefore, many technical divers carry a back up mask, though it’s considered optional equipment. (Some computers with audio alarms will alert you when you ascend beyond stop depth, making it another tool in this situation.)

2. A suitable back up is as small as possible.3. It is typically carried in a compact pocket as far to the rear as possible on the

right or left hip of the harness. [Show spare mask and location.]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 45 diver, you will be qualified to use EANx up to and includ-

ing 100 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 com-

bust 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.

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a. Example: Using an oxygen service regulator on a standard air cylinder – 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 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 equip-ment 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 decom-pression after long, deep dives. The use of higher oxygen probably lessens the risk of decompres-sion 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 other 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 cen-tral 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.

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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 including pure oxygen.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 support – 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 hand-ful – 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 manufacturer’s guide-lines 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 notwith-standing, 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 technical 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.

P. Maintenance1. You rely on your gear for life support. Therefore, maintain your gear according

to manufacturer specifications.2. Have regulators, valves, BCDs and gauges inspected and overhauled at least

annually or more frequently for heavy use or as manufacturer specified.3. Have any equipment that doesn’t appear to function normally inspected and

serviced before using.4. Never dive with gear in anything but top shape. To do otherwise in technical

diving raises your risk of injury or death by starting the dive with a potential problem.a. If you start a dive with some equipment in less than ideal working

order, you are essentially using your back up from the start of the dive.b. In this case, if your back up has no back up, then you’re diving without

back up. That’s what often injures and kills divers in technical diving environments.

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Q. Slates1. Usually a convenience in recreational diving, they are a necessity in

most technical diving for several reasons:a. Communication -- understanding between you and your team

mates may be crucial; if they don’t understand a signal, you need a slate

b. Memory back up -- you can’t rely on memory for crucial infor-mation; use a slate to record back up decompression schedules, turn around times, special procedures, etc.

c. You record your time, depth and gas supply throughout the dive.2. Choose a slate that fits easily in your thigh pocket (or other easily

accessed pocket) because you’ll use it frequently.3. You can use specialized slates for dive planning, surveying (cave/wreck

diving) and other plans; multiple page slates are a good choice for lots of writing space.

R. Jon line1. Decompressing in a current on an anchor/mooring line can be tiring, also

crowded if several divers reach the same deco stop at same time.2. A jon line is a short line about a metre/three feet to 3 metres/10 feet long

that snugs (via a loop or special hook) around the anchor/ mooring line and clips to your harness.

3. The jon line lets you decompress effortlessly, opens up space at the stop depth and helps you control your depth. Also reduces likelihood of get-ting blown off the line in a very strong current.

[Show class jon lines and how to attach them.]S. Multigas computers

1. You can program multigas computers with two or more enriched air blends or oxygen, then tell the computer when you’ve switched gases during the dive. The computer adjusts the decompression limits, required decompression, and oxygen exposure calculations based on the gas you’re actually using.

2. This provides several benefits:a. You can conveniently make gas-switch, extended no stop dives as

a way of giving yourself substantial no decompression time.b. You can accelerate your decompression to reduce your hang time.

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c. You don’t need to calculate oxygen exposure manually as you do when making gas switch dives using a single gas computer.

3. Multigas computers accommodate from three to 10 different gases; some require a PC interface with desktop deco software.

4. More about multigas computers shortly.T. Urination

1. In technical diving, long dives (two or more hours) and the inability to surface makes having to urinate a real issue, especially when wearing a dry suit.

2. There are three options available to males, two of which are available to females.a. Dive in a wet suit and wash the suit thoroughly after each dive.

• This is not an option in many environments due to water tem-perature or duration

• Urinating in a wet suit feels warm, but actually speeds heat loss by dilating skin capillaries

• This is an option for both male and female diversb. Adult diapers in dry suits

• Do not require any suit modification.• Have limited capacity -- they only hold so much.• Require that you relieve yourself slowly or it will leak into

your suit.• Are an option for both male and female divers.

c. Condom catheters in dry suits• Use disposable external urination condoms to route waste out-

side the suit through a valve.• Sometimes have valves that can only be opened and used face

down to avoid a squeeze.• Many not be suitable for pristine environments that would be

sensitive to contamination• Primarily are an option for males – attempts to make such

devices for females have had only limited acceptance, though some appear to work.

[Show student hardware for dry suit condom catheter, if available]

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Other Delivery Content, Tec 45-1Study assignment: Tec 45 Handout 1

III. equipment Issue Discussions and Philosophies

Learning ObjectivesBy the end of this section, you should be able to answer these questions:1. Why is the standard practice to use two multigas dive computers on the dive, and to plan with desk top decompression software?2. Why are DSMBs replacing lift bags in many tec diving situations?3. Why has failure of quick releases on harness shoulders proved not to be a serious issue? What would you do if it were to happen?4. What is perhaps the most common weighting error in tec diving?5. Why is backup buoyancy critical in most open water, open circuit technical diving?6. What are the problems with trying to use a lift bag or DSMB as a backup buoyancy system? 7. What is the policy of virtually every lift bag and dry suit manufacturer with respect to backup buoyancy?8. Why is the redundant (double bladder) BCD the most realistic approach to providing backup buoyancy control?

A. The standard of practice in deep decompression tec diving is to use multigas dive computers during the dive, with decompression software for overall planning. You may use a single gas computer and/or depth gauge and timer with tables in this course, but this is the recommended approach. There are several reasons why:1. Multigas computers now handle up to seven gas mixes (including trimix),

and also calculate CCR (closed circuit rebreather) diving, making them suited to your future as well as present tec diving.

2. A multigas computer maximizes your options in an emergency, allowing you, for example, to switch to a lower oxygen gas (even back gas) should you lose or exhaust your primary deco gas.a. Some of the newest models allow you to enter entirely new gases

during the dive and recalculate your decompression. This provides more options in an emergency.

3. Many multigas computers have PC interfaces, allowing you to adjust stop

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depths, conservatism factors, etc. Some let you choose the decompression model you prefer.

4. Multigas computers track your actual dive profile, adjusting your decom-pression requirements based on your actual dive. This makes it easier to adjust to circumstances. Example: You accidentally exceed your planned depth slightly; you leave the bottom sooner based on your computer so that your decompression time is the same as planned, keeping you within your gas plan.

5. With a multigas computer, you can choose to decompress based on a sin-gle gas and switch to a higher oxygen gas for added conservatism (as you learned to do as a Tec 40 diver). Should circumstances require (emergen-cy), however, you can switch to accelerated decompression to get to the surface faster with less gas used.

6. You still use deco software to plan the dive – oxygen exposure, decom-pression and gas requirements. Use the computer within the dive you plan.

7. Multigas computers are more sophisticated than single gas, so they’re more complex to use. But, they are not difficult to use and getting easier.

B. DSMBs (Delayed Surface Marker Buoys) are replacing lift bags in many tec div-ing situations.1. DSMBs stand higher in the water, making them preferred for rough condi-

tions.2. DSMBs are more compact on your rig, making them popular when used

as an emergency alert only.3. DSMBs have no-spill designs (though several lift bags have these, too,

now), so accidentally losing tension on the line isn’t likely to result in a spilled buoy.

4. The highest capacity DSMBs are essentially tall, thin lift bags and work well for drift decompression.

5. Several types of DSMBs (and lift bags) have LP inflation ports that allow you to fill them with an LP inflator hose, away from your body or mouth, without using a second stage. This minimizes the chance of regulator freeze, as well as minimizing reel tangle issues.

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C. At one time, some people thought failure of shoulder quick release buckles on tec harnesses would be a serious issue. This hasn’t proven true.1. Quick release buckles are designed to withstand hundreds of kg/lbs

direct stress. This explains why stress failure is virtually unheard of.2. Were the release to fail, you would only have to pass the lower part of

the harness strap through the D-ring on the upper part and tie it.D. Weighting

1. Proper weighting and adequate backup buoyancy remain two areas commonly addressed inadequately in open circuit technical divers.

2. Perhaps the most common weighting error in tec diving is under weighting.a. Proper weighting means you’re able to maintain your final stop

depth with nearly empty back cylinders and either no or near-empty deco cylinders – this is what would happen if you had a major problem forcing you into a long deco using your gas reserve, and/or decoing on back gas.

b. If you were not weighted for this, you face a high DCS risk, because you would not be able to remain at stops.

c. As an example, a properly weighted tec diver wearing high capacity doubles and two deco cylinders will be about 14 kg/30 lbs negatively buoyant at the start of a dive, and 4.5 kg/10 lbs or more negative at the end if dive goes as planned.

d. In this example, inadequate weighting would mean that in an emergency situation, besides the original problem, you also have to deal with between 4.5 kg/10lbs and 14 kg/30 lbs positive buoyancy while trying to decompress.

E. Backup buoyancy is critical in most open water, open circuit technical diving because a diver is substantially negatively buoyant throughout the dive.1. Failure of the primary BCD without a backup leaves no alternative but

to drop equipment (deco cylinders, weights, etc.). This can make the sit-uation worse if the diver must discard deco gases to attain buoyancy.

2. Discarding gear may result in too much buoyancy. If the diver is already in deco, the ability to decompress effectively becomes compromised, growing worse as the diver consumes gas.

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3. There is a high likelihood of surfacing with omitted decompression if the diver cannot maintain stop depths, or lacks the required decompression gases, or both.

4. A dry suit may work as a backup buoyancy device.a. This is primarily an option when the dive will be relatively short and

shallow, with short decompression – the gas requirement is low, so the diver is not substantially negatively buoyant (such as when using aluminum cylinders).

b. Limited option – most dry suits will not hold more than small amount of excess gas. Beyond a certain point, it escapes through neck/wrist seals.

c. Several manufacturers caution against inflating their dry suits to gain large amounts of buoyancy because of zipper failure issues.

d. A large volume of expanding gas is harder to control in a dry suit.e. With deeper/longer tec dives, backup buoyancy control other than

the dry suit is generally necessary.5. Some have advocated using a lift bag or DSMB as a backup buoyancy

device. This has several problems:a. DSMBs and lift bags are not designed as buoyancy devices and are

difficult to control in that role. • They are even more difficult to control while trying to per-

form gas switches, handle a gas shutdown, etc.• Even if learned and practiced, it is not a skill one would

expect a diver to perform reliably in a real failed BCD emer-gency over the course of a real decompression. If it has not been practiced at all, it would be especially difficult.

• DSMBs/lift bags do not provide a realistic buoyancy system for positive buoyancy at the surface after completing decom-pression.

• Using a DSMB/lift bag as back up buoyancy would require the diver to hold on to the bag while dealing with other tasks, or it would have to be clipped to the harness. Either would compromise safety.

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b. If the DSMB/lift bag is used for backup buoyancy, then it is not available to send to the surface.

c. Sending the DSMB/bag to the surface and hanging on the line for buoyancy is not a good option either.• In all but flat seas, this will cause the diver to rise and

fall, compromising the quality of the decompression.• Once sent up, there is no way to adjust the bag’s buoyan-

cy.• It is not a technique that transfers well to other environ-

ments.• Stress on the line and reel is a major issue. For this to be

reliable, the diver would need to carry much heavier line and a larger reel than most tec divers prefer.

d. Trying to use a lift bag or DSMB as a backup buoyancy system unnecessarily complicates an emergency situation, and provides inadequate benefit.

6. It’s worth noting that no dry suit manufacturer and no lift bag manufac-turer sanctions the use of their products as tec diving backup buoyancy devices. Some specifically warn against it.

7. The redundant (double bladder) BCD is the most realistic approach to providing backup buoyancy control.a. They are designed for the job and endorsed by the manufactur-

ers.b. They are used the same way as your primary BCD – a well prac-

ticed skill you use on every dive, exactly what you want in an emergency situation.

c. They are applicable to virtually all dive environments.d. Other than a slightly higher investment, there are no meaningful

drawbacks.e. They are the only real option for open water tec diving in a wet

suit.

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exercise, Other Delivery Content, Tec 45-11. Multigas computers have become the standard of practice in tec diving because (choose all that apply)q a. they handle multiple gases and CCR diving.q b. they maximize your options in an emergency.q c. their decompression models are newer than those in single gas computers.q d. they are smaller than single gas computers.2. DSMBs are replacing lift bags in many tec diving situations because (choose all that apply)o a. they don’t stick so far up into the wind.q b. they are more compact on your rig.q c. they have no-spill designs.q d. some have special inflation systems.3. It is unlikely that a quick release on your harness shoulder would fail, but if it did, you would only need to tie off the loose end.q Trueq False4. Perhaps the most common weighting error in tec diving isq a. under weighting.q b. over weighting.q c. neutral weighting.q d. None of the above.5. Backup buoyancy control is critical in open water, open circuit tec diving because if you’re properly weighted and your primary BCD fails, you risk being unable to decompress adequately.q Trueq False6. Problems with trying to use a lift bag or DSMB as a backup buoyancy system include (choose all that apply)q a. it is a complex skill with low reliability for use under stress after disuse.q b. it is difficult to conduct that skill and other complex skills at the same time.q c. hanging from a floating DSMB/lift bag may compromise the quality of decompression.q d. hanging from a floating DSMB/lift bag requires a heavier line/reel than tec divers like

to use.

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7. Several manufacturers endorse the use of the lift bags/DSMBs are emergency backup buoyancy devices.q Trueq False8. The redundant (double bladder) BCD is the most realistic approach to providing backup buoy-ancy control because (choose all that apply)q a. they were designed specifically for this purpose.q b. you use them exactly like you use your primary BCD – a practiced skill.q c. it is applicable to almost all dive environments.q d. other than a slightly higher cost, it has no meaningful drawbacks.How did you do?1. a, b. 2. b, c, d. 3. True. 4. a. 5. True. 6. a, b, c, d. 7. False. 8. a, b, c, d.

Iv. Gas PlanningManual Supported Content

Study assignment: Tec Deep Diver Manual, pgs 93-97, Determining Gas Supply and Reserve Requirements for Multiple Depths and Decompression Stopspgs 146 -161, Gas Planning III, Tec Exercise 3.2

Learning ObjectivesBy the end of this section, you should be able to answer these questions:1. How do you determine your gas supply and reserve requirements for a multiple depth dive (including dives with decompression or safety stops)?2. What is the theoretical cause of gas narcosis?3. How do you account for narcosis in dive planning?4. What depth limits arise from narcosis concerns?5. How do you perform an “air break” and why should you do so?6. How do you determine your OTUs and OTU limits for a given dive profile?7. How do you calculate your “CNS clock” exposure for a given dive profile and determine its limits?8. How do you include oxygen concerns in determining the ideal enriched air to use at a given depth?

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9. What is the basis of oxygen surface interval credit, and how do you apply it?You should also be able to:10. Calculate the gas supply requirements and oxygen exposure for a decompression dive based on a single gas computer using enriched air and/or oxygen during decompression for conservatism.

A. As a Tec 40 diver, you learned to use desk top decompression software to plan your gas requirements and oxygen exposure. This is the state of practice, but as a Tec 45 diver, you should understand more specifically what the software does for you. We’ll start with a review of what you learned already.

B. Determining gas supply and reserve requirements for multiple depths and decom-pression stops.1. To determine the gas you need for a given depth, you multiply your SAC by

the number of minutes at that depth and by the conversion factor for that depth:

gas required = SAC X min X conversion factor

a. You get the conversion factor from the SAC Conversion Factor Table in the Appendix of the Tec Deep Diver Manual. (Round up to the next depth if the exact depth isn’t shown.)

b. The conversion factor is simply the absolute pressure in atmo-

spheres:

Metric: (D in metres + 10) / 10 Imperial: (D in feet + 33) / 33

MetricExample: 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

ImperialExample: 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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2. You do this for each depth and then total all the required gas.a. Use the DSAT TecRec Dive Planning Slate to list depth, conversion

factor and required gas (as well as other information to be filled in later).

b. If making a gas switch, note each gas type as well.c. You use the midpoint between bottom and the first stop for the

ascent depth, and the time of the ascent to the first stop. (Subtract the stop depth from the bottom depth, divide that by two and add it to the stop depth to find the midpoint).

d. Ascent between stops accounts for minimal gas use and is handled several ways. Most common (used in examples) in manual calcula-tion is to add one minute every third stop (gas switches are ignored), which accommodates rates as slow as 10 m/30 ft per minute. Ascent from last stop to surface is generally disregarded in gas calculations.

e. Recall that your SAC is typically higher on the bottom (working) portion of the dive and lower during the decompression portion of the dive.

f. Determine a planned gas volume consumption for each gas you’ll use.

g. Typically round to closest litre or cubic foot.3. Get your total gas requirements by multiplying the planned consumption for

each gas by 1.5 (for thirds – or use the formula you learned earlier for a dif-ferent reserve)

Examples: [Have students complete the appropriate portions of the DSAT TecRec Dive Planning Slate; tell them to disregard the col-umns not used here – they’ll learn about those later.]

MetricWhat is your total gas requirement, including one third reserve, if your SAC rate is 20 litres per minute and you plan a dive to 30 metres for 15 minutes followed by a 3 minute safety stop at 5 metres, using air for the entire dive? Ascent rate is 18 metres per minute.Answer: 2103 litres

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Total Air = 1200 + 112 + 90 = 1402; 1402 X 1.5 = 2103 litres

MetricYou plan to make a dive with air by following a standard air table. You plan to make the decompression more conservative by using EANx50 at 9 and 6 metres, and pure oxygen at 3 metres. Your planned dive is 45 metres for 40 minutes, with 5 minutes at 9 metres, 19 at 6 metres and 33 at 3 metres. Your SAC rate is 24 litres per minute during the working part of the dive, and 18 litres per minute when decompressing. Your ascent rate is 10 metres per minute. What are your total gas requirements for each gas, includ-ing a one-third reserve?Answer: Air = 8452 l, EANx50 = 1077 l, Oxygen = 1194 l

Air = 5280 + 355 = 5635; 5635 X 1.5 =8452

EANx50 = 171 + 547 = 718; 718 X 1.5=1077Oxygen = 796 X 1.5=1194

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ImperialWhat is your total gas requirement, including one third reserve, if your SAC rate is .75 cubic feet per minute and you plan a dive to 100 feet for 15 minutes followed by a 3 minute safety stop at 15 feet, using air for the entire dive? Ascent rate is 60 feet per minute.Answer: 78 cubic feet

Total Air = 45 + 4 + 3 = 52; 52 X 1.5 = 78 cubic feet

ImperialYou plan to make a dive with air by following a standard air table. You plan to make the decompression more conservative by using EANx50 at 30 and 20 feet, and pure oxygen at 10 feet. Your planned dive is 150 feet for 40 minutes, with 5 minutes at 30 feet, 19 at 20 feet and 33 at 10 feet. Your SAC rate is .8 cubic feet per minute during the working part of the dive, and .65 cubic feet per minute when decompressing. Your ascent rate is 30 feet per min-ute. What are your total gas requirements for each gas, including a one-third reserve?Answer: Air = 282 cf, EANx50 = 39 cf, Oxygen = 44 cf

Air = 176 + 12=188; 188 X 1.5=282EANx50 = 6 + 20 = 26; 26 X 1.5=39Oxygen = 29; 29 X 1.5=44

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[Work examples based on tables generated with software you’ll use in the course and have students calculate the gas require-ments.]

4. Your calculations will likely vary somewhat from what your desk top decompression software gives you. The differences should be minor, how-ever, and result from variations in calculating ascents, rounding, etc.

C. Narcosis -- theory and application1. As you already know, your END (Equivalent Narcotic Depth) does not

change with different blends of enriched air.2. Without going into deep physiological theory, the basic explanation for

narcosis is that gas dissolved into nerve cell lipids interferes with nerve impulse transmission.a. Gas solubility varies with different gases; the higher the solubility,

the higher the expected potential for narcosis.b. Oxygen is twice as soluble as nitrogen; suggesting that it is poten-

tially more narcotic than nitrogen. This is offset somewhat by your body metabolizing oxygen.

c. Argon is more soluble than nitrogen or oxygen, and highly narcot-ic, making it (along with high density) a poor choice as a breathing gas.

d. Helium has poor solubility, which is thought to explain why it does not produce narcosis easily.

e. The relationship between solubility and narcosis isn’t perfect; physiologists still don’t understand all the mechanisms underlying narcosis.

3. Because oxygen and nitrogen have roughly equivalent narcosis, the END does not change when the oxygen-nitrogen ratio changes. A blend contain-ing helium, however, would be less narcotic at a given depth than air or enriched air, and therefore have a lower END.

4. You must realize that narcosis is present on all dives -- in theory, it begins to affect you as soon as you drop below the surface, though when using oxygen/nitrogen, its effects don’t become noticeable for most divers until approaching the 30 metres/100 foot range.a. Diving with some narcosis present is acceptable (and practically

speaking, unavoidable), provided it doesn’t impair you.

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b. Proper training allows you to function properly with some narcosis present -- the use of step-by-step procedures (NO TOX switches, for example) not only speed learning, but aid proper functioning -- what seems simple at the surface may not be as simple under stress on a deep dive. Note that many procedures such as NO TOX gas switches take place at significantly shallower depths than 30 metres /100 feet, where narcosis is not an issue for most divers.

c. Diving substantially impaired can be one of the primary hazards of deep tec diving (even when using helium blends) -- be conservative when dealing with narcosis.

5. You account for narcosis in dive planning by limiting your dives to appropri-ate depths based on:a. Safety -- Your primary concern is that you note and react quickly and

properly to emergencies. If you’re so narked (under the influence of narcosis) that to react quickly and properly to an emergency is ques-tionable, ascend immediately to a shallower depth. It may take some time for your head to clear.

b. Individual susceptibility -- Narcosis affects different people differently at different times. You’re more likely to be affected adversely when:• you’ve not made a deep dive recently.• you’re attempting new tasks and/or are task loaded.• you implement an emergency procedure you’ve not practiced

recently.• you’re subject to environmental stress (cold, dark, overhead

environment).• you’re less than optimally fit.

c. Individual adaptation -- You’ll be more able to function appropriately despite narcosis when:• you’ve been diving regularly, working up to the depth progres-

sively.• your mission and the dive requirements are not complex.• you’ve practiced emergency procedures extensively and regu-

larly.• you’re diving in good environmental conditions.• you’re in optimal physical fitness.

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6. You must adjust your depth limits based on the above considerations, but the technical diving community generally observes the following narcotic limits when using air or enriched air:a. 40 metres/130 feet – this is the limit for recreational diving, and the

limit for technical penetration (penetration beyond 40 linear metres/130 linear feet from surface).

b. 50 metres/165 feet – this is the general limit for open water technical diving, particularly for less experienced technical divers. Much of the European dive community has used this as its limit for decades, with a good track record. This limit for air is acknowledged by the HSE (Health and Safety Executive) in the UK, by SPUMS (South Pacific Underwater Medical Society), and by the commercial diving industry in the USA.• This is the outside limit, with the trend in some areas toward

using trimix at shallower depths to manage narcosis and gas density/carbon dioxide issues more conservatively.

• This limit is not generally accepted for cave environments or wreck penetration; for those activities, you would use trimix beginning at least at 40 metres/130 feet.

c. 56 metres/185 feet – This is the1.4 ata PO2 limit for air diving; few tec communities recommend diving this deep with air any longer, though it was the accepted limit for a long time.

7. As a technical diver, it is your responsibility to adjust your maximum depth based on how narcosis and other variables affect you on a dive. In a warm, tropical sea with clear water, 50 metres/165 feet on air may be acceptable, but the same depth in a cold, dark lake or in strong current, etc., may be too deep. During the dive, you may need to limit depth shallower than you planned if you or a team mate find narcosis becoming too strong. It’s your responsibility to adjust accordingly.

D. Managing Oxygen Exposure1. Air breaks – These are breaks on air/lower oxygen EANx while decompress-

ing on oxygen or EANx at a depth that yields a PO2 of 1.6 to give your body a rest from the high oxygen exposure.a. Air breaks have been found to greatly reduce the risk of a CNS toxic-

ity convulsion. Therefore, you should consider them standard prac-tice. You don’t have to limit them to PO2 of 1.6 bar/ata. Most divers perform air breaks at lower PO2s as well.

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b. The typical air break is five minutes on air (or lowest oxygen gas available) for every 25 minutes of decompression. Do not include the 5 minutes in your decompression time when following a tables-based accelerated decompression schedule.

• Switch a multigas computer to the break gas when on an accelerated computer deco schedule. Computer will continue to calculate deco and oxygen exposure.

c. Some desk top deco software programs can include air breaks in the tables they generate.

2. Calculating OTUs.a. As you learned as a Tec 40 diver, the OTU (introduced by Dr. Bill

Hamilton as an extension of the previous UPTD [Unit Pulmonary Toxic Dose] method) is a method for measuring your oxygen “dose” for a given dive.

b. Based on the formula: OTUs = minutes x ((PO2-0.5)/0.5)0.83

c. You can use the formula, but it’s much simpler and less error prone to use desk top deco software, which calculates automatically, or tables such as the Equivalent Air Depth and Oxygen Management Table. Multiply OTU per minute for the given blend at depth by the number of minutes. Round down to the next deeper depth if the actual depth is not shown. You do this for all depths (including your ascent and decompression/safety stops) and total them to get your OTUs for the dive. Note: You accumulate no OTUs when your PO2 is .5 or less.

d. OTU limits appear on the Oxygen Limits Table in the Appendix of the Tec Deep Diver Manual.• Total OTUs per day varies depending on number of contin-

uous days of diving. This is based on the body’s ability to recover from oxygen exposure. Example: If diving only one day, 850 OTUs for this day are permissible. If diving five days in a row, a total of 2300 OTUs, or an average of 460 OTUs per day, is the maximum.

• OTUs on a day may exceed the daily average, provided that the total OTUs for the period does not exceed the

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allowable OTUs for the Mission. Example: Five days div-ing has 2300 Total OTUs for the Mission, average 460 per day. If the first day exposes you to 700 OTUs, you have a total of 1600 OTUs (2300-700=1600) to divide among the remaining four days.

• Note: “Average OTUs per Day” is not a daily allowance. That is, you cannot have 850 day one, 700 day two, 620 day three, etc.

• If you ever don’t know what the OTU daily limit is (no table is available), the daily OTU limit for continuous days forever is 300 OTUs.

• Some tec divers simply use 300 OTUs as their daily limit and don’t worry about the longer allowances. This simpli-fies calculations and is generally adequate for many tec diving situations.

e. To calculate your OTUs and limits for a dive, total all the OTUs for each planned depth based on the gas blend and time, making sure the total is within the allowable OTUs. (After the dive, you total the OTUs for the actual dive to use in planning subsequent dives).• Calculating OTUs (and “CNS clock”) includes calculating

the descent, the ascent and all decompression.• Normally you disregard air breaks in calculating OTUs.• When your PO2 is less than .5 ata you accumulate zero

OTUs. [Note: Go through the following using the Equivalent Air Depth and

Oxygen Management Tables for PO2 and OTU per minute. Have students fill in the Depth, Time, Gas, PO2, OTU/min, OTUs columns on their Dive Plan Slates.]

MetricExample : You’re planning three days of diving, and this is the first dive of the second day. You ended yesterday having used 705 OTUs, and you know you’ll need 700 OTUs for the dives planned on the third day. You plan to dive to 30 metres on air and decompress using EANx40 at 6

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metres and oxygen at 3 metres as a decompression “pad” following the air-only schedule. Your planned bottom time is 40 minutes, and the tables you plan to use require 8 minutes of decompression at 6 metres and 26 minutes at 3 metres. Your ascent rate is 10 mpm. What are your OTUs for the dive? If you make only this dive today, do you have enough OTUs for tomorrow? If not, how many more do you need? If yes, how many do you have to spare after this dive if made as planned? Answer: 71.2 OTUs for the dive. Yes. You would have 383.8 OTUs left for the second day after this dive.

Total allowed for 3 days = 18601860 - 705 (day 1) - 700 (day 3) = 455 OTUs available for day 2. 455 - 71.2 = 383.8 OTUs left.

ImperialExample: You’re planning three days of diving, and this is the first dive of the second day. You ended yesterday having used 705 OTUs, and you know you’ll need 700 OTUs for the dives planned on the third day. You plan to dive to 100 feet on air and decompress using EANx40 at 20 feet and oxygen at 10 feet as a decompression “pad” following the air only schedule. Your planned bottom time is 40 minutes, and the tables you plan to use require 8 minutes of decompression at 20 feet and 26 minutes at 10 feet. Your ascent rate is 30 fpm. What are your OTUs for the dive? If you make only this dive today, do you have enough OTUs for tomorrow? If not, how many more do you need? If yes, how many do you have to spare after this dive if made as planned? Answer: 71.6 OTUs for the dive. Yes. You would have 383.4 OTUs left for the second day after this dive.

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Total allowed for 3 days = 18601860 - 705 (day 1) - 700 (day 3) = 455 OTUs available for day 2. 455 -71.6 = 383.4 OTUs left.

3. Calculating the “CNS clock”a. You can calculate the “CNS clock” much the same way you calcu-

late OTUs -- by using desk top deco software, or by using tables to determine the CNS percent per minute.• Note that some programs and tables extrapolate NOAA

limits to more increments on the “CNS clock” than others; this may produce some differences in what different pro-grams and tables produce.

• As with OTUs, you normally disregard air breaks in calcu-lating the “CNS clock.”

b. Total the CNS for each depth and time as with OTUs.

[Note: Go through the following using the Equivalent Air Depth and Oxygen Management Tables for PO2 and CNS% per minute. Have stu-dents fill in the Depth, Time, Gas, PO2, CNS% per minute and CNS per-centage columns on their Dive Plan Slates.]

MetricExample: You dive to 33 metres using EANx32 for 65 minutes. The EANx32 tables you’re using call for a 15 minute stop at 6 metres and 40 minute stop at 3 metres. You plan to use 100 percent oxygen at these stops to maximize your conservatism. Your ascent rate is 10 metres per minute. What is your “CNS clock” at the end of the dive?Answer: 99.8%

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ImperialExample: You dive to 110 feet using EANx32 for 65 minutes. The EANx32 tables you’re using call for a 15 minute stop at 20 feet and 40 minute stop at 10 feet. You plan to use 100 percent oxygen at these stops to maximize your conservatism. Your ascent rate is 30 feet per minute. What is your “CNS clock” at the end of the dive?Answer: 99.8%

4. Oxygen exposure and ideal enriched air blenda. You learned in the Tec 40 course that you could choose the “ideal”

gas based on the blend that allows the highest fraction of oxygen without exceeding a PO2 of 1.4 at the desired depth.

b. You also learned that previous oxygen exposure can affect this gas choice if you won’t have enough oxygen exposure time remaining to make the dive. In such a case, you must choose a blend with less oxygen.

Example: As part of a 15 day dive series during which you’re keep-ing your OTUs within the accepted daily average (300), you plan a repetitive dive to 21 m/70 ft for 45 minutes. At the start of the dive, your CNS clock is 80% and you have 240 OTUs for the day. The “ideal” blend would normally be EANx45, but 45 min at 21m/ 70ft yields 72.9/73.8 OTUs and 30% CNS, putting you over your CNS

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and OTU limits. Using EANx32, however, 45 minutes at 21m/70ft yields 45 OTUs and 14.8% CNS, keeping you within limits.

c. Remember that regardless of whether your repetitive dive is a gas-switch, extended no-stop dive or a decompression dive, you need to account for oxygen exposure at all levels with all gases.

d. An alternate method to calculate the “CNS clock” is to divide the actual time by the single exposure time for that PO2 on the NOAA Oxygen Exposure Limits listed on the Oxygen Limits Table in the appendix of the DSAT Tec Deep Diver Manual.

Example: In calculating a dive, you will spend 10 minutes at 30 metres/100 feet using EANx32. What is your “CNS clock” percentage for that part of the dive? Answer: 5.5% -- Limit for 1.3 PO2 = 180 min; 10÷180 = .055 = 5.5%• You may use this method for each level and PO2 as an alternative

to the previously described percent-per minute techniques.• Both give you approximately the same answers -- you may find

insignificant variations due to rounding.5. Oxygen surface interval credit for the “CNS clock.”

a. Between dives breathing air, your body begins to reverse the chemical effects of oxygen.

b. The OTU system accounts for this in its mission/daily average methodolo-gy. For the CNS “clock,” there’s surface interval halftime credit (similar to dive table credit).

c. CNS surface interval credit was initially based on studies of hospital patients undergoing long term oxygen exposure.• Though not based on divers initially, the CNS surface interval credit

system, when also used with the OTU system, has a good field record in diver use

• Different computers, desk top deco software and tables use different halftimes for this -- 90 minutes is the “standard” halftime, but some default to a slightly less conservative 60 minutes (you can usually set it higher, though)

• CNS surface interval credit not commonly used with recreational enriched air diving, because you almost never reach oxygen expo-sure limits doing no stop dives with EANx40 or less

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d. You apply your credit several ways:• Enriched air computers and desk top deco software will calcu-

late your credit for you. (Not all computers/ programs give credit.)

• You can use a table such as the CNS Surface Interval Credit Table in the Appendix of the Tec Deep Diver Manual. Find your CNS percentage at start of surface interval along the side, and where your interval falls along the top. Where they inter-sect is your new CNS percentage, which you add to the CNS percentage you accumulate during the next dive. (If your per-centage isn’t shown, round up to the next greater.)

Example: After the first dive, your CNS was 68%. After an hour and 40 minutes, you make your second dive, which accumulates 43% “CNS clock” time. What is your CNS percentage after the dive?Answer: 78%. After 1:40 surface interval, 68% (round to 70%) yields 35%. 35% + 43% = 78%.

e. As with any table, software or computer, stay well within limits and be conservative.

E. Planning a decompression dive: using a single gas computer1. This discussion takes what you learned as a Tec 40 diver and extends it to

doing the planning by hand. You’ll use what you learn for extended no stop dives and accelerated decompression dives as well.

2. Recall that the simplest way to plan a decompression dive is based on a single gas, using gas switches for conservatism. Using a multigas computer, you pro-gram it with all your gases, but leave it set for your bottom gas throughout the dive, including the decompression. This has several advantages:a. Maximum conservatism -- keeps you well within decompression

model limits.b. Simplicity – the computer generates required decompression and

guides you through the dive.c. Not based on max depth -- decompression is based on actual profile

rather than the deepest depth, which can reduce overall decompression time.

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d. Gas flexibility -- since the computer assumes you’re decoing based on your back (bottom) gas, you can deco on back gas or any other gas with an equal or greater oxygen fraction (within its oxygen limits). This lets you use whatever gases you have avail-able for the dive, and makes it easier to handle a deco gas prob-lem (becoming lost, regulator malfunction, etc.).

e. Easy back up decompression -- by using a second computer of the same type, and/or backup tables.

f. Accelerated decompression option -- you can switch your com-puter to the gases you’re actually decompressing with (or, for a single gas computer, you can carry accelerated decompression tables based on the gases you’ll use) for emergency get-out-of-the-water-sooner situations (such as a leaking dry suit). Keep in mind that compared to using EANx/oxygen following an air schedule, accelerated deco is a trade – a less conservative decompression for less time decompressing.

3. The flexibility makes it a good method for gaining experience with decompression diving, which is why you learned it at the Tec 40 level and continue to use it at the Tec 45 level.

4. To plan oxygen exposure and gas requirements, use a dive table (or gen-erate one with desk top deco software) based on making the entire dive, including deco, using the bottom gas. But, you must calculate oxygen exposure based on the actual gases you’ll use, and gas requirements based on your SAC rates and the times at each depth.

[Note: Go through the following profile with students, having them complete the entire Dive Planning Slate (except runtime) with you and using the various tables in the Tec Deep Diver Manual. Ask guiding questions so that as a group, the class finds the answers rather than you simply providing them.]

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MetricExample: You plan a dive to 44 metres using a single gas enriched air computer set for EANx26. You plan to decompress using EANx80 from 9 metres to the surface. You estimate that your bottom time will be 40 minutes. Your dive tables for EANx26 show that 40 minutes at 44 metres requires 3 minutes decompression at 12 metres, 10 at 9 metres, 17 at 6 metres and 43 at 3 metres. Your ascent rate is 10 mpm. Your SAC rate is 19 litres per minute on the working part of the dive, and 16 lpm (litres per minute) when decompressing.• Following the rule of thirds, how much of each gas do you need for this dive? Answer: 6771 litres of EANx26; 2489 litres of EANx80• If you have twin 18 litre cylinders with 170 bar of EANx26 do you have enough EANx26 for the dive? If you have a 13 litre cylinder with 205 bar of EANx80, do you have enough EANx80 for the dive? How much do you have of each? Answer: No and yes. 6120 litres EANx26; 2665 litres EANx80• What are your OTUs and “CNS clock” after the dive? Answer: OTUs=161.5; CNS%=85.1%• If you’ll be diving again in two and a half hours, and you’ll be staying within the mission averages for three days of diving, how much “CNS clock” time and how many OTUs can you have on the second dive? Answer: Allowable CNS = 64%; allowable OTUs = 459.2

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EANx26 = 4180+228+106=4514 l; 4514 X 1.5 = 6771 litresEANx80=304+461+894=1659 l; 1659 X 1.5 = 2489 liters18 litres x 170 = 3060 litres, 3060 x 2 (doubles) = 6120 litres EANx2613 litres x 205 = 2665 litres EANx80OTUs = 66.8+3.2+0.6+18.1+26.11+46.0=160.8“CNS clock” = 33.2%+1.3%+0.4%+22.2%+9.9%+18.1%=85.1%After two and a half hours, CNS 85.1% = 36%; 100%-36%=64%Three day mission allows 1860 OTUs, average 620 per day. 620-160.8 = 459.2

ImperialExample: You plan a dive to 145 feet using a single gas enriched air comput-er set for EANx26. You plan to decompress using EANx80 from 30 feet to the surface. You estimate that your bottom time will be 40 minutes. Your dive tables for EANx26 show that 40 minutes at 145 feet requires 3 minutes decompression at 40 feet, 10 at 30 feet, 17 at 20 feet and 43 at 10 feet. Your ascent rate is 30 fpm. Your SAC rate is .8 cubic feet per minute on the work-ing part of the dive, and .65 cf when decompressing.• Following the rule of thirds, how much of each gas do you need for this dive? Answer: 285 cubic feet of EANx26; 101 cf of EANx80• If you have twin 104 cf cylinders, working pressure 2400 psi, with 2500 psi of EANx26 do you have enough EANx26 for the dive? If you have a 104 cf cylinder, working pressure 2400, with 2300 psi of EANx80, do you have enough EANx80 for the dive? How much do you have of each? Answer: No and no. EANx26 = 216 cf; EANx80 = 100 cf (99.8)• What are your OTUs and “CNS clock” after the dive? Answer: OTUs=160.4; CNS%=85.1%• If you’ll be diving again in two and a half hours, and you’ll be staying within the mission averages for three days of diving, how much “CNS clock” time and how many OTUs can you have on the second dive? Answer: Allowable CNS = 64%; allowable OTUs = 458.3

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EANx26=176+9.6+4.3=189.9 cf; 189.9 X 1.5=285 cfEANx80=12.4+18.7+36.3=67.4 cf; 67.4 X 1.5 =101 cf2500/2400 = 1.04, 1.04 x 104 = 108 cf, 108 x 2 (doubles) = 216 cf2300/2400 = .96, .96 x 104 = 100 cf (99.8)OTUs=67.6+3.2+0.6+18.2+26.1+46.0=161.7“CNS clock” = 33.2%+1.3%+0.4%+22.2%+9.9%+18.1%=85.1%After two and a half hours, CNS 85.1% = 36%; 100%-36%=64%Three day mission allows 1860 OTUs, average 620 per day. 620-161.7 = 458.3

6. [Have students compare their results with the same profile(s) calculated with desk top decompression software.] Again, minor variations between your hand-calculated plan and what decompression software provides are normal.

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v. Turn Around Points and environmental variablesManual Supported Content

Study assignment: Tec Deep Diver Manual, pgs 167-172, Turn Around Points and Environmental Variables, Tec Exercise 3.4, questions 2-4

Learning ObjectivesBy the end of this section, you should be able to answer these questions:1.What are turn around points, and how do you determine them?2. How do you learn to account for environmental variables such as current, visibility, temperature and waves when planning a tec dive?3. What are four guidelines to consider when planning a tec dive in an unfamiliar envi-ronment?

A. Turn around points1. You learned as a Tec 40 diver that all dives have turn around points, which

are points in the dive at which you and your team agree to turn the dive around and head up/back to the exit.

2. When you or a team mate reaches any turn point, you turn the dive. Factors to consider when determining turn around points include:a. completing your decompression within your gas planning without

using your reserve.b. the effects of total exposure time (temperature, fatigue).c. the effects on repetitive dives, if any (OTUs, CNS, deco require-

ments).3. All dives have at least two turn around points:

a. a turn around point based on bottom timeb. a turn around point based on gas consumed -- the SPG reading at

which you turn around is called “turn pressure”4. Dives may have other turn around points based on the mission, logistics or

unknown variables in the profile. These may include:a. Distance -- you turn when you’ve traveled an approximate maxi-

mum distance from the exit.b. Task completion -- when you accomplish your mission, the team

may agree to turn immediately to minimize decompression.c. Depth -- the team agrees to turn the dive upon reaching a certain

depth.

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d. Depth/time combinations -- the time turn around point varies with the maximum depth to accommodate decompression within the planned gas supply; example: The planned depth is 36 metres/120 feet, we’ll turn at 65 minutes. If we exceed that, we’ll use 40 metres/130 feet as the maximum depth and turn at 50 minutes.• Respect your turn around points.• Note that exceeding your time usually affects your decom-

pression more than does exceeding your depth.[Show students a table example of exceeding depth limit slightly and time limit slightly for the same dive and com-pare decompression increases.]

e. KISS -- Keep it Super Simple. Too many turn around points gets complicated -- keep it to only a few that cover the plan require-ments.

5. As you recall, calculating your back gas turn pressure means finding the pressure at which you begin your ascent with enough gas to complete your planned decompression (including the proportion that will use back gas) and still have one third (or other planned reserve) of your back gas remain-ing.a. Start by determining your total back gas volume requirements (bot-

tom plus decompression), including reserve. Determine what cylin-ders you’ll be using to have this volume, and their fill pressure.

b. Now determine how much pressure (bar/psi) you’ll use breathing that volume, and subtract that from your starting pressure.

c. For metric, divide the volume you’ll use on the bottom by the cylin-der capacity, then subtract that from the starting pressure.

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Metric:Turn pressure = Start pressure - (bottom volume ÷ cylinder capacity)Example:Previously, you planned a dive to 44 metres using a single gas enriched air computer set for EANx26. You plan to decompress using EANx80 from 9 metres to the surface, with an estimated bottom time of 40 minutes. Your dive tables for EANx26 showed that 40 minutes at 44 metres requires 3 minutes decompression at 12 metres, 10 at 9 metres, 17 plus one minute at 6 metres and 43 at 3 metres. Your ascent rate is 10 mpm. Your SAC rate is 19 litres per minute on the working part of the dive, and 16 lpm when decompressing. The gas volume results were:

Following the rule of thirds, you determined you need 6771 litres of EANx26. To meet this requirement, you will dive in twin 21 litre cylin-ders filled to 162 bar. This gives you 6804 litres of gas (21 x 2 x 162 = 6804). By what pressure should you be starting your ascent so that you will have a one third reserve after completing your decompression?Answer: 62.5 bar 4180 ÷ 42 (twin 21 litre cylinders) = 99.5; 162-99.5 = 62.5 bar.

d. For the imperial system, the baseline method is the easiest way to find your turn pressure. Divide the bottom volume by the baseline, and subtract that from the starting pressure.

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Imperial:Turn pressure = Start pressure - (bottom volume ÷ cylinder baseline)Example:Previously, you planned a dive to 145 feet using a single gas enriched air computer set for EANx26. You planned to decompress using EANx80 from 30 feet to the surface. You estimated that your bottom time will be 40 minutes. Your dive tables for EANx26 show that 40 minutes at 145 feet requires 3 minutes decompression at 40 feet, 10 at 30 feet, 17 plus one minute at 20 feet and 43 at 10 feet. Your ascent rate is 30 fpm. Your SAC rate is .8 cubic feet per minute on the working part of the dive, and .65 cf when decompressing. The gas volume results were:

Following the rule of thirds, you determined you need 285 cf of EANx26. To meet this requirement, you will dive with twin 140 cubic foot 2400 working pressure plus-rated (10% overfill) cylinders filled to 2640 psi. This gives you 308 cubic feet of gas (140 x 2 = 280, 280 + 28 (10% over-fill) = 308). By what pressure should you be starting your ascent so you will have a one third reserve after completing your decompression?Answer: 1136 psiBaseline = .117 (280/2400 = .117)176 ÷ .117 = 1504; 2640 - 1504 = 1136

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e. As a shortcut many divers use the “half + 15 bar/200 psi” rule -- take half your doubles pressure and add 15bar/200 psi. You should be ascending by then. This generally works well (actually conservative-ly, if you compare to previous examples) when most of your decom-pression will be made with deco cylinders. If you will use back gas for more than the first one or two stops, calculate as shown above to be sure you’ll be starting up with ample gas for decompression plus reserve.

f. Most desktop deco software does not calculate turn pressure because it doesn’t know what size cylinders you’re using. Therefore, you need to calculate it yourself (but desktop deco software, of course, will calculate the volume requirements, making it a simple process).

g. For sidemount, turn pressure is the same, however, you switch between your primary cylinders until you reach the turn pressure in each. Some divers will swap every 15 – 20bar / 200 – 300psi, which has the advantage of keeping the pressure close in case the gas in one cylinder would become unavailable (more on this later). Other divers will swap every 50bar/500 psi, which reduces task loading by reduc-ing the number of regulator exchanges. It is also the most intuitive interval on most SPGs).

B. Environmental variables1. Tec diving is like recreational diving in that the procedures and techniques

vary with the environment.2. Many of the techniques and procedures you learn in this course will be area

specific, just as they were where and when you became an Open Water Diver.

3. When tec diving in a new area, as in recreational diving, you want an orien-tation to the new area and any special procedures and techniques that apply to it from an experienced local tec diver, ideally a technical diving instructor.

4. The following guidelines will help you minimize difficulties when making tec dives in a new environment.a. Gain experience with a new environment before making challenging

tec dives in it. Make recreational and/or no stop dives initially.b. Master new, area specific equipment and procedures in controlled

conditions before applying them on more challenging tec dives.

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c. Consult local tec divers. Local methodologies evolve based on local needs; just because something works well in one environment doesn’t mean that it’s suited to another.

d. Recognize the difference between local methods and inappropriate methods. In the DSAT Tec Diver course, you learn principles that apply universally to manage your risk in the tec environment. The application method may vary, but the principles remain. Disregarding them is not a “local method.” Example: Divers in an area commonly diving to 60 metres/200 feet using standard recreational single cylin-ders and regulators does not constitute a local tec diving method because it ignores having at least two independent regulators in a technical environment.

v. Team DivingManual Supported Content

Study assignment: Tec Deep Diver Manual, pgs 173-175, Team Diving III, Tec Exercise 3.5

Learning ObjectivesBy the end of this section, you should be able to:1. Demonstrate the hand signals for:

• line• entanglement• reel• I think I’m bent• question• Turn the dive.

2. Identify where your team mates rank in your chain of back up systems.You should also be able to answer these questions:3. What is the one back up your team mates provide that you cannot provide yourself?4. What are the duties of a safety/support diver?

A. More tec diving hand signals [Demonstrate the following:]1. line2. entanglement

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3. reel4. I think I’m bent5. question6. Turn the dive.

B. In recreational diving, your team mate is your primary back up system (first in the back up chain). In tec diving, your team mate is not your primary back up system.1. In tec diving, you rely on yourself first and have back ups for everything.2. Therefore, your team mate is second, third or even further into your back up

chain, providing a back up only if your self reliant back ups fail.3. The exception is that your team mates provide your “back up brain,” which

is the only back up you can’t provide yourself.a. This means you and your team mates dive paying attention to limits,

the plan and what’s going on. You dive as though you might have to finish the dive alone; no one follows everyone else blindly.

b. Team mates signal each other if they notice anything out of sorts. They remind each other to check gas supplies, time, depth, etc.

c. Team mates never assume that another is either right or wrong. If they disagree about what’s happening or what to do, they resolve the confusion or end the dive if they can’t.

C. The duties of the safety/support diver1. Part of team diving often involves handling support tasks and safety.

This is especially true when you’re less experienced. Interacting with more experienced divers is a great way to learn.

2. A safety/support diver generally (but not always) stays within the no stop limits and attends to divers decompressing.

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3. Safety/support diver duties may include, but are not limited to:a. Checking on divers, assuring they have ample gas, etc.b. Shuttling gear. Up – exhausted stage/deco cylinders, unneeded

equipmen. Down – extra gas, weights, etc.c. Watching for and locating divers separated from their teams.

Notifying teams that missing divers are located.d. “Baby-sitting” -- hovering near decoing divers to be ready to

assist.e. Sitting standby on the boat or shore, fully geared up and ready

to go in to assist in an emergency.f. Coordinating the boat crew with the needs of the decoing div-

ers.g. Shuttling communications between the divers and surface sup-

port.

Tec 45 Knowledge Development TwoI. Thinking Like a Tec DiverManual Supported Content

Study assignment: Tec Deep Diver Manual, pgs 176-179, Thinking Like a Tec Diver III, Tec Exercise 3.6

Learning ObjectivesBy the end of this section, you should be able to answer these questions:1. What assumption do technical divers make when they plan a dive?2. What is a “trust me” dive and why do technical divers avoid them?3. What do technical divers do with superfluous equipment in an emergency?4. How do you “think backwards” to assist with planning for possible emergencies?5. What are six principles for surviving a tec dive?A. Self sufficiency

1. By now, you’ve learned that you dive self sufficiently -- your team mate is a back up only after your back ups fail.

2. Tec divers plan their dives assuming that they may have to complete a dive alone, separated from the rest of the team.a. Thinking this way guides you to plan a self sufficient dive.b. Self sufficiency helps you manage risk, because you’re better prepared

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to handle problems unaided if necessary.c. Though self sufficient, tec divers work in cohesive teams to maintain

the “back up brain” teamwork.3. A “trust me” dive is a dive in which one diver relies on another to complete

the dive safely. Tec divers avoid them, because on a “trust me” dive, you dive using your “back up brain” only, and separation from the leading diver may make it impossible to complete the dive safely.a. Following a more experienced diver is not necessarily a “trust me”

dive if you could, at any point in the dive, abort and complete it with-out assistance.

b. “Trust me” dives usually result when divers attempt dives well beyond their experience and training.

c. Ask yourself whether you could, in an emergency, finish the dive alone, or reasonably expect to assist a team mate, at any point during the dive.

B. Equipment is disposable1. Tec divers invest a lot in their gear and in maintaining it.2. However, they also consider it disposable in an emergency. Anything that’s

superfluous to handling an emergency and completing a dive gets ditched immediately.

3. Tec divers don’t allow themselves to get attached to their gear, and they don’t cut corners due to cost. If it doesn’t do the job, replace it, no matter how new or expensive. Nothing in diving is worth a serious injury or death.

C. Thinking backwards1. As a Tec 40 diver, you learned to “think backwards” to anticipate problems

when planning a dive. Let’s look at this philosophy more closely.2. Dive planning and emergency preparation is a mental process based on

anticipating the mission needs and preparing for realistic problem scenarios.3. A good strategy for emergency planning is to include thinking backwards in

your dive planning.

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a. Imagine you’re at the furthest point in your dive.b. Imagine realistic problems -- that might stand between you and return-

ing safely to the surface.c. For each one, think about what you need to survive the dive indepen-

dently.d. Make sure you have those resources.e. Caution: Don’t create a problem by carrying gear or following a proce-

dure in trying to solve an unrealistic problem.4. Work one problem at a time, and beware of “paralysis through analysis.” Think

things through and then move on.D. Principles for surviving a tec dive

1. You learned these principles as a Tec 40 diver. Refer to them constantly as you plan, execute and review your tec dives.

2. Never intentionally violate any of these principles. If you have a question about what you or your team should do or not do, or use or not use on a tec dive, these principles will usually guide you to the answer.

3. The principle of gas reserve -- you should have ample gas to handle reasonably possible emergencies and still complete your decompression (usually thirds).

4. The principle of self sufficiency -- at any point in a dive, you should be able to complete it independently.

5. The principle of depth -- your dive plan should account for narcosis, decom-pression, oxygen toxicity and gas supply needs based on a planned depth and/or a maximum contingency depth that you do not exceed.

6. The principle of simplicity -- your dive should be planned as simple as possi-ble, with complexities eliminated.

7. 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.

II. Gas Planning

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Manual Supported ContentStudy assignment: Tec Deep Diver Manual, pgs 194-201, Gas Planning IV, Tec Exercise 4.2

Learning ObjectivesBy the end of this section, you should be able to answer these questions:1. What are the procedures for staging and switching gases when making gas-switch, extended no stop dives?2. What do you do if you cannot switch to your shallower gas blend, or if you must switch back to the deeper blend when making a gas switch, extended no stop dive?3. How do you plan and make a gas-switch, extended no stop dive using desk top decom-pression software?4. How do you plan and make a gas-switch, extended no stop dive using a multigas comput-er?5. How can you make a gas-switch, extended no stop dive more conservative?6. How do you make a safety stop while within a decompression stop?7. What is “runtime,” how do you determine it, and how do you use it?8. What do you do if you find yourself slightly ahead of your runtime?9. What is “gas matching”?

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A. Gas-switch, extended no stop dives1. As you recall, a gas-switch, extended no stop dive is a dive in which

you gain bottom time by ascending to a shallower level and switching to a richer EANx. This gives a longer no stop time that takes full advan-tage of a tec diver’s extended gas supply through both the multilevel profile and the gas switch.a. The no stop increase is substantial, usually with so much time

that even using multiple cylinders, you can stay well within no stop limits.

b. Although a no stop dive, this is considered tec diving because of the equipment and procedures required, which include breathing more than one gas, NO TOX switches, etc.

c. Especially when diving shallower than 40 metres/130 feet for the first level, gas-switch extended no stop dives work well with single cylinders for back gas.

d. It is possible, though not common, to make gas-switch, extended no stop dives with more than two blends.

2. Procedure -- requires desk top deco software and multigas computer.a. Can be done as a tables based dive, but the most common prac-

tice is to plan with deco software and execute with a multigas computer.

b. Choose a back gas based on the bottom depth and a richer gas in a stage cylinder based on the second level depth being above its maximum depth (1.4).

c. Start the dive at the deepest point. When you reach a particular point (usually dive time or particular pressure), you ascend to second level and NO TOX switch to stage cylinder.

d. You remain on stage cylinder and stay at or above second level depth for the rest of the dive.

e. You may carry the stage cylinder throughout the dive if neces-sary, but if feasible, to minimize the possibility of oxygen toxici-ty, stage it at the second level depth as you head down and retrieve it upon returning. If you must carry it, a mouth block is a good reminder in addition to the required markings.

f. Plan an appropriate reserve in both cylinders, but since you stay

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within no stop limits and can head up at any time, a 35-70 bar/500-1000 psi reserve is usually adequate.

3. If, for some reason you can’t make the gas switch, you end your dive accord-ing to the no stop limits/oxygen limits of your back gas.

4. If, for some reason, you have a problem with your shallow blend, you must obviously switch to your back (deeper) gas.a. This is simple with a multigas computer – switch back to the bottom

gas and finish/shorten your dive staying within no stop limits.b. If following a table, you may be beyond the deepest depth, no stop

limits for your back gas, but you are still in a no stop situation. Start your ascent immediately, make a safety stop and end the dive.

5. Desk top deco software allows you to write tables for planning gas-switch, extended no-stop dives.a. Used most commonly to plan dives you will make with a multigas

computer.b. Enter your first depth, EANx and desired time within no stop limits.c. Enter your second level, second EANx and find your no stop limit

(you may be limited by oxygen instead of no stop time). When in doubt, assume and plan for a deeper second level as opposed to a shallower one.

d. Have the program generate tables based on your variations in your deepest depth/time. Use these to plan your dive.

e. If making a tables-based dive, carry backup tables based on having made the entire dive on back gas in case you cannot switch for some reason.

[Show class planning for gas switch, extended no stop dive using software.]6. Multigas dive computers simplify gas-switch, extended no stop dives.

a. Choose the blends for the depth levels and enter them into the com-puter per manufacturer instructions.

b. Start with your deepest depth and blend. You switch gases on the computer after you ascend to the next level and NO TOX switch to the richer EANx.

c. If you must switch back to back gas for some reason, switch your computer and it automatically gives your new no stop times.

d. Although the multigas computer calculates automatically, you’ll still

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use desk top deco software to assist with dive planning. It is the only way to estimate your gas supply requirements.

e. Have two multigas computers, or carry backup tables/time/depth gauges.

7. Making gas-switch, extended no stop dives more conservative:a. The easiest way is to stay well within no stop limits; ascend and

switch well before reaching the deeper level limits.b. Plan your dive based on EANx blends with somewhat less oxy-

gen than you actually use. (E.g., use in EANx30 and EANx40 in your desk top/multigas dive computer, but dive with EANx32 and EANx45.)• Be sure not to exceed maximum depths for the blend.• You’ll need to track oxygen exposure for each dive and

repetitive dives separately (manually or with desk top deco software), because your dive computers don’t know what you’re really breathing.

c. Some dive computers allow you to set them to provide more conservative no stop limits.

B. Safety stops within decompression stops1. As a recreational diver, you learned to make safety stops – a stop at 5

metres/15 feet for three to five minutes not required by your tables or computer, for added conservatism.

2. Tec divers make safety stops by extending their last deco stop by five minutes. E.g., your table says you require nine minutes at 3 metres/10 feet, so you stay 14, or your computer clears you to surface, and you stay another five minutes.

3. After surfacing from a particularly strenuous dive or long deco dive, “safety stop” at the surface by resting in the water for five to 15 minutes before exerting yourself (such as climbing aboard or ashore in heavy gear).a. You may continue to breathe EANx or oxygen. Remember that

even though you’re at the surface, if you’re breathing EANx50 or higher, the CNS clock is running and you’re gathering OTUs.

C. Runtime

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1. Runtime is a continuous elapsed time schedule you follow from the begin-ning to the end of the dive when following a table. It accounts for your descent, ascent, decompression time and tells you where you should be against elapsed time.a. Diving based on runtime is a common method of following a table.

Because it doesn’t work well for dive computer based decompression (nor is it necessarily needed), runtime isn’t used as commonly as it once was.

b. Runtimes can be useful, however, for planning a mission with multi-ple teams, because it helps establish an approximate common time base for coordinating efforts.

2. To use runtime, you depart from the depth when you reach the elapsed time listed for that depth.

3. You create runtime by adding the times for each dive phase (descent time is usually included in bottom time) and deco stop in sequence, including ascent time (round minutes to the closest whole minute, up or down). a. Desk top deco software will generate runtime automatically, some-

times with less rounding.b. Desk top deco software may list arrival times by repeating the depth

(arrival time and departure time).c. When generating multiple tables, some programs will generate run-

times for alternative schedules as well as the planned one.4. Example: You’re making a 30 minute dive to 30 m/100 ft using air and your

table calls for a stop for one minute at 6 m/20 ft and 15 minutes at 3 m/10 ft. Your runtime would be:

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5. Runtime is simple to follow, but if you find yourself slightly ahead of your runtime (you leave a bit early, for example), adjust to merge grad-ually with the runtime. If you’re behind your runtime, you usually switch to the next longer deco schedule.

Example: Using the previous runtime, you leave the bottom at 29 min-utes. You merge by ascending slightly slower than usual so that you reach 6 m/20ft in 3.5 minutes, and then stay 1.5 minutes at the stop to the 34 minute mark.

6. Air breaks and gas switches when you return to back gas don’t count as decompression time. You handle this by: a. using a dive watch with a stopwatch function and stopping the

runtime during air breaks/gas switches.b. adding air breaks and switches into your runtime.c. using desk top deco software that automatically includes air

breaks. Also, you can revise the provided runtime by manually adding in air break/gas switch times.

7. Runtimes work well with tables-based gas-switch, extended no stop dives. Your runtime shows the point by which you must ascend from each deeper level to the next shallower level. If you go up ahead of the time indicated, the dive becomes more conservative than planned, so you can still follow the runtime without adjustments.

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D. Gas matching1. Gas matching is a method (used primarily in overhead environments – cave,

wreck) to account for teams with members who have different breathing rates and cylinder sizes. It’s not generally needed in open water because you can generally begin an ascent quickly in an emergency. However, it can be useful if, due to current for example, you want to be sure you and your team mate can return to the anchor line to ascend while sharing as..

2. Gas matching helps assure that should the diver with a higher gas supply and SAC rate have complete loss of gas supply at the furthest penetration point, a team mate with a smaller gas supply and lower SAC rate would have suffi-cient gas for both divers to exit.

3. To gas match (based on one third reserves), the diver with the smaller gas supply needs to reserve a volume equal to one third of the larger gas supply.

4. To do this in metric:a. Take the volume of the larger gas supply and divide by three. This is

the amount that must be reserved by the diver with the smaller sup-ply.

b. Divide the reserve by capacity of the smaller gas supply cylinders. The result is the reserve pressure that the diver with the smaller gas supply should have left at the end of the dive if there’s no emergency.

c. Subtract the reserve pressure from the actual pressure of the smaller cylinders, divide that by two and subtract it from the full pressure to get the one-third turn around point for the smaller gas supply.

Example: You’re diving with twin 11 litre cylinders with 200 bar. Your team mate has twin 21 litre cylinders with 160 bar. What should your reserve pres-sure be, and what’s your one-third turn around pressure?Answer: 102 bar reserve pressure; 151 bar turn aroundTeam mate’s volume = 21 x 2 x 160 = 6720 litres.Reserve = 6720 ÷ 3 = 2240 litres.Reserve divided by your cylinder capacity = 2240 ÷ 22 (11 x 2) =102 bar reserve you should have left200 - 102 = 98 bar you can use; 98 ÷ 2 = 49; 200 - 49 = 151

5. To do this in imperial:a. Determine the baseline for each set of doubles, and determine the gas

volume in each.

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b. Divide the largest volume by three. This is the amount that must be reserved by the diver with the smaller supply.

c. Divide the reserve volume by the baseline of the smaller cylin-ders. The result is the reserve pressure the diver with the smaller gas supply must maintain.

d. Subtract the reserve pressure from the actual pressure of the smaller cylinders, divide that by two and subtract it from the full pressure to get the one-third turn around point for the smaller gas supply.

Example: You’re diving with twin 80 cubic foot cylinders, working pressure 3000 psi, with 2950 psi in them. Your team mate has twin 120 cubic foot cylinders, working pressure 2400 psi, with 2350 psi in them. What should your reserve pressure be, and what’s your one-third turn around pressure?Answer: 1473 psi reserve pressure; 2213 turn pressureTeam mate’s baseline = .1 (240 ÷ 2400 = .1);Team mate’s volume = 235 cf (2350 x .1);Your baseline = .053 (160 ÷ 3000 = .053).Your volume = 156 cf (3000 x .053 = 156)Team mate’s (larger volume) reserve = 235 ÷ 3 = 78.3.78.3 ÷ .053=1477; 2950 - 1477 = 1473, 1473 ÷ 2 = 736.5;2950 - 737=2213

6. Remember that even if you don’t need to gas match, you must determine your actual gas supply before each dive to be sure you have enough gas, plus reserve, to make the dive.

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III. emergenciesManual Supported Content

Study assignment: Tec Deep Diver Manual, pgs 202-209, Emergencies IV, Tec Exercise 4.3

Learning ObjectivesBy the end of this section, you should be able to answer these questions:1. How do you ensure you don’t lose your deco cylinders, and what should you do if you do?2. What do you do if your dive goes deeper and/or longer than your planned dive?3. How can you use a single gas dive computer to back up a multigas computer?4. What should you do if you miss a decompression stop?5. What should you do if you have a delay in your ascent to a decompression stop?6. What should you do if you omit some or all of your decompression?7. What should you do if you run out of gas?8. What is a “drift kit,” when would you use it and what items would you have in it?9. How do you handle a lift bag that spills as it ascends but cannot be pulled back down to redeploy?

A. As a Tec 40 diver, you learned about some of the emergency procedures covered in this section, but for that level. As a Tec 45 diver, you learn additional considerations to address the longer/deeper dives you’ll be qualified to make.

B. Lost decompression cylinders1. Losing your deco cylinders can leave you without a complete solution, so the

emphasis is on prevention.a. Never stage your cylinders if you have any question whether you’ll

be able to return to them and retrieve them.b. Don’t stage cylinders where other divers might take the “lost” cylin-

ders they “found.” c. Be sure that you stage cylinders where they won’t roll, float or get

swept away. Clip them to something or otherwise secure them if pos-sible.

d. As you learned, confirm that the valves are closed, but regulator pres-surized, on the staged cylinders.

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2. If you do lose your cylinders, how difficult your situation would be depends on how much decompression you have and whether it’s based on accelerated decompression or not. The primary issue will be whether you have enough gas volume.a. If your decompression is based entirely on your back gas and your

deco cylinders held higher oxygen for conservatism, then you decompress on back gas. If you don’t have enough back gas, you can use any EANx blend with as much or more oxygen than your back gas, so a team mate or support diver may be able to assist.

b. If you’re making an accelerated decompression, leave your multigas computer set for back gas. If backing up your computer with tables, be sure to carry single gas back up tables as well as accelerated decompression tables.

c. If you have support divers, they may be able to bring down standby cylinders.

d. When making accelerated deco dives, if using a multigas computer and your team mates have not lost their deco gases, they can give you what’s left of theirs as they finish. They’ll finish before you, but you should be able to complete your decompression.

3. If you don’t have enough gas in your doubles to complete your decompres-sion, decompress as long as you can. When you surface, breathe emergency oxygen and contact emergency medical care if you suspect DCI (either DCS or AGE) symptoms.

C. Exceeding your planned depth and time1. This shouldn’t be an “emergency” but a situation. You should prepare for

this as a regular part of dive planning (as you’ve already been practicing).2. Use decompression software for times and depths greater than and less than

your planned dive so you can see how they affect required decompression and gas volumes.

3. The rule of thirds will generally accommodate the next longer/ deeper schedule, but you should compare the gas requirements to be sure.

4. Be prepared to alter time to accommodate depth. If you find yourself deep-er than planned, turn the dive sooner. Again, also remember that exceeding your bottom time usually creates a higher decompression penalty than slightly exceeding your planned depth.

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5. Precision diving is the key -- you must master buoyancy control and closely monitor depth, time and gas supply. Dive well and this won’t be an issue.

D. Backing up a multigas computer with a single gas computer (continued).1. Though not ideal, you can back up a multigas computer with a single gas

computer by setting the single gas computer for your back gas. Decompress as if using back gas, with the higher oxygen blends for conservatism.

2. However, if conditions might require accelerated decompression (E.g. due to water temperature or gas volume), then carry accelerated deco tables generat-ed by desk top deco software and use a single gas computer for time and depth information only (or a depth gauge/time, of course).

E. Missed decompression stop1. If you miss a decompression stop, how you handle it depends on the situation.2. If you can, immediately (less than a minute) redescend and complete the stop

and add one minute, then decompress according to schedule.3. If you cannot redescend (such as if you have a gas supply problem and must

switch to a deco cylinder you can’t use at the deeper depth), stay at the next stop for the combined time of both stops.

4. If you cannot redescend or it takes longer than a minute to do so, extend your 6 metre/20 foot stop and/or the final stop by 1.5 times the decompression nor-mally required. (Note: some dive computers calculate missed deco stop proce-dures automatically – see the manufacturer’s instructions.)

5. If you’re using a dive computer, it may lock up if you skip a stop and cannot redescend to complete it. You may need to decompress according to back up tables.

F. Delay in ascent to decompression stop1. A delay in ascent while following a dive computer is not an issue because the

computer will adjust your decompression requirements.2. If you’re delayed ascending to your first decompression stop while using

tables, add the delay to your bottom time and decompress according to the new schedule.

3. Using tables, delays between stops aren’t usually as critical unless they’re excessive (more than two or three minutes). Do not count the delay as decom-pression time.

4. When you’ve had a delay in ascent, it’s always wise to extend your last stop as much as practicable.

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G. Omitted decompression1. The seriousness of omitted decompression depends on the situation.

a. Omitting all required decompression has high DCS risk, espe-cially if it’s greater than five or ten minutes.

b. The more decompression you’ve completed, the less risk (obvi-ously).

c. If decompressing with a single gas computer/table and using EANx/oxygen for conservatism, your risk is relatively low if you’ve completed most of your decompression.

2. If you omit decompression from 6 metres/20 feet or shallower, if you have no DCS symptoms and it’s possible, return to depth within one minute, add a minute and complete your decompression as scheduled. As a precaution, extend your last stop several minutes or more.

3. If you omit decompression from 6 metres/20 feet or shallower, and if you have no DCS symptoms but it takes longer than one minute to return to your stop depth, extend your 6 metre/20 foot stop and/or the final stop by 1.5 times the decompression normally required (or longer on the final stop, as possible).

4. If you omit decompression from deeper than 6 metres/20 feet, return to the first stop depth as quickly as possible (ideally less than five min-utes) and decompress according to the schedule up to and including the 12 metre/40 foot stop. Extend the 9 metre/30 foot stop and all shallow-er stops by 1.5 times their scheduled times.

5. If you cannot return to depth (no gas available, for instance), breathe emergency oxygen, remain calm and monitor yourself for DCS symp-toms. If you surfaced owing more than a few minutes decompression or skipped all your decompression, assume you will get bent and have your team begin preparing for emergency evacuation. If possible stay on 100 percent oxygen until reaching emergency medical care.

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H. Running out of gas1. Running out of gas should be a rare event if you plan your reserve appropri-

ately. Unexpected exertion or a sudden freeflow can cause you to exhaust gas faster than expecteda. You should not run out of gas on the bottom, because you should be

ascending to your first stop depth before it happens.b. Your first option is to see if your team mates or support divers can

help by sharing gas or bringing some down.c. With a multigas computer, you can switch to back gas and continue

to decompress, though it will take longer.d. If you exhaust a deco gas using tables and you have another, higher

oxygen deco gas, ascend to the first stop where you can use it. Combine your missed stops with the stop at that depth, unless this will prematurely exhaust that gas, too. In that case, follow the decom-pression schedule and extend the shallower stops as much as practi-cable.

e. If you are following a single (back) gas deco schedule with a higher oxygen deco gas for conservatism, you can switch to back gas or any other gas with as much or more oxygen as your back gas (provided you’re shallower than the maximum depth).

f. As a general guideline, if gas termination interferes with your decom-pression, decompress as long as you can as best you can with what you have. Stay down with team mates’ high oxygen deco cylinders after they complete decompression, if possible. Even if you end up getting DCS, the more decompression you complete, the less severe it should be.

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I. Drift kits1. A drift kit is an emergency kit you carry in open ocean where you could

end up adrift in current a considerable distance from the dive boat. The most elaborate kits are watertight/pressure proof containers bracketed to the doubles; the simplest are items in a pocket or pouch.

2. You use your drift kit if you surface and cannot see the dive boat, or it is too far away to reach and you’re having trouble getting the crew’s attention.

3. At a minimum, a drift kit contains an inflatable signal tube (may be a DSMB) and whistle, or other visual and audible signaling devices.

4. In higher risk current environments, you may considera. signal mirrorb. watertight flasherc. portable PLB (Personal Locator Beacon -- allows authorities to

find you electronically when activated.)d. smoke flares; flares, aircraft dyee. collapsible radar reflector

J. Partly spilled lift bag/DSMB1. If you send up a lift bag without sufficient line tension, it can partly

spill at the surface, leaving it too buoyant to pull down and redeploy, but insufficiently buoyant for use as a firm decompression line. A spilled DSMB (unlikely with no-spill designs) may not stand upright for maximum visibility.

2. First option: As you’ve practiced, send up a team mate’s lift bag/DSMB clipped to the same line via a carabineer or large bolt snap (small snaps can hang up). Using same line combines their lift and avoids entangle-ment from two lines in water.

3. Second option: team mate deploys own lift bag/DSMB with separate reel.

4. Final option: use the bag as is -- you’ll have to be more careful with buoyancy.

K. The DSAT Emergency Procedures Slate summarizes missed decompression stop, delay in ascent and omitted decompression procedures so you can have them with you when diving.

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Learning ObjectivesBy the end of this section, you should be able to answer this question:1. Why may you set a multigas computer for gas blends you don’t plan to use on a dive?

L. More on using multigas computers in emergency situations1. You do not have to use a gas just because you set your multigas dive com-

puter for it. 2. Dive computers that support a large number of gases can be set for gases you

don’t plan to use, but that would be available for use in an emergency. This gives you more gas options in the event of an emergency.a. Example: Deco gases used by another team that will be diving along

with your team may be different from your team’s, but available for sharing.

b. Example: Air is readily available in many dive environments, so support divers could bring it for decompression use if nothing else were quickly obtainable.

3. The main drawback to having your multigas computer set for gases you don’t plan to use is that you have to be sure you don’t select one of the con-tingency gases by accident.

4. Some of the newest computers will allow you to enter a new gas during the dive should you need to do so in an emergency situation. The computer can then calculate your decompression accordingly.

exercise, Other Delivery Content, Tec 45-21. You might set a multigas computer for gas blends you don’t plan to use during a dive so your computer can calculate your decompression with them in an emergency situation.q Trueq FalseHow did you do?1. True.

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Tec 45 Knowledge Development ThreeI. Homemade equipmentManual Supported Content

Study assignment: Tec Deep Diver Manual, pgs 192-194, Equipment IV, Tec Exercise 4.1

Learning ObjectivesBy the end of this section, you should be able to answer these questions:1. Why would technical divers use “homemade” equipment?2. What are examples of acceptable and unacceptable instances in which a tec diver might use “homemade” gear?3. What are six general guidelines regarding the use of “homemade” equipment?4. What is probably the most common “homemade” item used by tec divers?

A. Because tec diving is evolving rapidly and taking on new challenges, it’s not unusual for tec divers to have to create special equipment for special purposes, or adapt something for an underwater need.

B. This is considered acceptable for equipment that is not critical for safety and/or life support, and for which there exists no professionally made version.1. Acceptable examples might include specialized compass slates for map-

ping, bungee-clip arrangements for securing accessories, binder rings for attaching laminated deco tables to slates, etc.

2. Unacceptable examples might include a BCD or regulator, line reel, lift bag, etc.

C. The following six guidelines apply to “homemade” items:1. Be sure you really need it. Keep things simple.2. Confirm that a professionally made version does not exist.3. It should provide a clear benefit or meet an important need, yet not cre-

ate a hazard nor be essential to safety and life support.4. Try the item during some no stop, simple dives before using it on a

demanding tec dive.5. Get an opinion from one or more experienced tec divers whom you

respect.6. When in doubt, do without it.

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D. The most common “homemade” item is probably the custom dive table generated by desk top deco software and then laminated or printed on waterproof paper for use during the dive.

II. Thinking Like a Tec DiverManual Supported Content

Study assignment: Tec Deep Diver Manual, pgs 210-211, Thinking Like a Tec Diver IV, Tec Exercise 4.4

Learning ObjectivesBy the end of this section, you should be able to answer these questions:1. What do tec divers mean when they say they “never stop learning”?2. What four attitudes characterize leading tec divers?3. What is the biggest myth told about diving with certain methodologies or in certain envi-ronments?4. Why is methodology situational?

A. Tec diving continues to evolve, with new methodologies and technologies arising quickly.1. Competent tec divers recognize that their learning never stops.2. Besides continuing education courses, tec divers avidly read online and print

dive magazines, underwater scientific and technical literature, and other information sources for new developments.

3. Tec divers pay attention to new ways of doing things as they interact with fellow tec divers. They also analyze each dive after the fact and make a con-scious effort to distill new learning from it.

4. Tec divers say they “never stop learning,” meaning that education in techni-cal diving never ends, and that every tec dive is part of it.

B. Four attitudes characterize leading tec divers. It’s worth noting that these character-istics tend to typify leaders in most areas of exploration.1. Humility -- they realize that they don’t know everything, and that there may

be more than one right way to do something. Their ego doesn’t get in the way of learning, doing or teaching.

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2. Open mindedness -- they never reject something just because it’s new or different, and they listen to other viewpoints. They don’t fear change and they’re not threatened by differing opinions.

3. Analytical -- they try to accurately and realistically weigh the merits of a technology or procedures for themselves and never accept something just because it’s new or because someone else thinks it’s better. They try to not let what they like, dislike or want to believe influence their con-clusions.

4. Competent -- while they’re open to change and alternative ways to do things, their own methodologies are solid and they can demonstrate a rationale and realistic basis for each. They’re quietly confident about how they dive, and they don’t choose their methodologies based on “looking cool” or what someone else might think or say.

C. The biggest myth in diving (tec or recreational) is that learning to dive in a spe-cific environment or with a specific methodology qualifies you to dive every-where.1. Methodology (including its technology) is situational, because each sit-

uation imposes differing demands. E.g. A three hour dive in 27°C/80°F water wouldn’t require a dry suit, whereas in 10°C/50°F water it defi-nitely would.

2. The suggestion that mastering one methodology or environment meets all diving circumstances presupposes that the methodology addresses all possible variables, or that the environment imposes all possible vari-ables. This isn’t possible. Example: a deep lake dive may be very cold, dark and eerie, but it cannot have the challenge of oceanic currents.

3. The basic methodologies and configurations you learn in this course form the foundation for a wide variety of technical diving circumstanc-es. However, you must learn specifics for the tec environment you actu-ally dive from your instructor, the local tec community and from experi-ence gained by broadening your limits slowly and carefully over many dives.

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III. Accelerated Decompression and Deep StopsManual Supported Content

Study assignment: Tec Deep Diver Manual, pgs 222-227, Oxygen Window and Accelerated Decompression, Deep Stops, Tec Exercise 5.1

Learning ObjectivesBy the end of this section, you should be able to answer these questions:1. What is the “oxygen window”?2. How does the “oxygen window” relate to accelerated decompression?3. Why is it that when decompressing with 100 percent oxygen, you can complete the decom-pression time for a 3 metre/10 foot stop as deep as 6 metres/20 feet without having to adjust your decompression time for the depth change?4. How do you use desk top decompression software and/or multigas computers to calculate accelerated decompression dives?5. How do you plan backup decompression information for an accelerated decompression dive?6. How do you choose which gas blends to use for an accelerated decompression dive?7. What are “deep stops,” how do you apply them and what might the benefit be of doing so?

A. Oxygen window and accelerated decompression1. Oxygen is metabolically active -- the body consumes it for energy production

and in other reactions. It contributes only minimally to DCS -- far less than gases such as nitrogen or helium.

2. When you ascend, the drop in ambient pressure causes a pressure differential (gradient) between the pressure of the dissolved inert gas (nitrogen) in your tissues and the pressure of the inert gas in your lungs. This is what causes the nitrogen to dissolve out of your tissues. However, as you know, you can’t ascend too far (on a decompression dive) or the ambient pressure drops so much that nitrogen may form bubbles in the tissues before it can dissolve harmlessly out through circulation and the lungs.

3. However, as you’ve also learned, if you shift to a higher oxygen gas (or pure oxygen) during ascent and/or decompression, you create a higher gradient between the dissolved inert gas (nitrogen) in your tissues and in your lungs without decreasing the ambient pressure.

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4. This causes nitrogen to dissolve out of the tissues faster without increasing bubble formation risk. This oxygen-derived gradient is called the oxygen window. a. You can use it to speed up your decompression without ascending to

an unsafe depth. b. This is the basis for accelerated decompression.c. EADs illustrate what’s happening.

E.g.: Your first decompression stop is at 9 metres/30 feet. If you switch to EANx50, your EAD is two metres/seven feet. Therefore, nitrogen leaves your body as if you were only two metres/seven feet deep, without ascending that shallow (which would probably cause DCS).

d. Accelerated decompression reduces your exposure to cold water and boredom.

e. It’s known that the shorter the required decompression, the more reli-able it is.

f. You can enjoy these advantages and still make your schedule conser-vative.

5. The greatest oxygen window comes from breathing pure oxygen (6 metres/20 feet and shallower). Note that with 100% O2, the EAD is always minus 10 metres/ minus 33 feet and you’re releasing nitrogen faster than if you were at the surface breathing air.

6. This is why, when using 100% oxygen, you can complete stops shallower than 6 metres/20 feet at 6 metres/20 feet without having to recalculate deco time. With any EANx blend, you must recalculate with tables; using a multi-gas computer, your deco time will be longer at the deeper stop depth. Note that you cannot ascend from the 6 metre/20 foot stop earlier than scheduled.a. This can have logistical advantages (staying below waves, boat traf-

fic, etc.)b. There may be some theoretical advantage in minimizing bubble for-

mation.c. It’s common when using pure O2, after completing the 6 metre/20

foot time, to ascend to 5 metres/15 feet for the 3 metre/10 foot stop. This takes advantage of the added depth but drops the oxygen expo-sure somewhat.

d. A 5 metre/15 foot stop has become common, in place of the 3 metre/10 foot stop; even when not using O2 you can take your stop at

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5 metres/15 feet when using a dive computer, or by setting your desk top deco software to create the final stop at 5 metres/15 feet instead of 3 metres/10 feet. (This is why you’ve been making 5 metre/15 foot stops in training dives.)

B. Calculating and planning accelerated decompression dives1. You calculate accelerated deco dives using desk top deco software much like

calculating gas-switch, extended no stop divesa. You compare decompression and gas requirements for possible depth/

time combinations using different deco gases to find those most use-ful for the situation.

b. Calculating your gas supply requirements is important to assure that you have ample gas to decompress. Dealing with your gas supplies is usually more flexible, however, because deco is shorter for the same dive.

2. The optimal way to plan and make an accelerated decompression dive is to have desk top deco software to estimate what schedule you get from your multigas dive computer, then making dive using two multigas computers based on the plan.a. If software isn’t available, then plan your dives based on your back

gas, noting the actual deco time on the dive. Keep notes in your log-book and use the same deco gases when doing this so you gradually learn how much bottom time you can have and still surface with one-third of your deco gases remaining.

[Demonstrate these concepts on desk top deco software by comparing the deco times for a dive to 50 metres/165 feet for 40 minutes using air for the entire dive to the same decoing with EANx50 starting at 21 metres/70 feet and oxygen at 6 metres/20 feet.]

C. Making accelerated deco dives more conservative.1. When diving from desk top deco software generated tables, you can:

a. Use the tables for the next greater depth and/or time than actually called for.

b. Generate the tables based on blends with less oxygen than actual (note that you will need to determine actual max depths and oxygen exposure)

c. Make a safety stop within the last decompression stop.

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2. When using a multigas computer you cana. Set the computer to be more conservative (if possible with your

model). If it doesn’t have such a setting, you can adjust the alti-tude; setting it for a higher altitude than actual will make it more conservative.

b. Set the blends for less oxygen than actual (note that you will need to determine actual max depths and oxygen exposure your-self).

c. Stay well within all limits given by the computer.d. Make a safety stop within the last decompression stop.

D. Planning back up for accelerated decompression dives1. A drawback to an accelerated deco dive is that you must have your deco

cylinders to decompress.2. You can use desk top deco software to write alternative emergency

tables for decoing without your deco cylinders. With multigas comput-ers, you simply stay on the blend you’re using.a. It may be difficult to make the desired dive and decompress

using only back gas. If so, accounting for this is crucial in going through A Good Diver’s Main Objective Is To Live.

b. As you learned earlier, if in doubt it’s less risky to keep your deco cylinders with you.

c. As you learned earlier, sometimes you can set multigas comput-ers for blends you don’t plan to use, but that may be available in an emergency situation.

E. Choosing deco blends1. Using desk top deco software, you’ll find that the shortest decompres-

sion comes from switching to the highest possible oxygen at each stop.2. This is usually impractical (if you have four stops, you would need four

deco cylinders) and you usually don’t gain much.3. For shallower dives, a single cylinder is usually adequate (Tec 45). For

dives to 50 metres/165 feet (Tec 50) to 65 metres/210 feet (Tec Trimix 65), you seldom benefit much by having more than two deco blends. Below that depth (Tec Trimix Diver) three or more decompression cyl-inders aren’t unusual to accelerate decompression and to provide the gas volume.

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a. Remember KISS (Keep It Super, Simple) principle -- simpler is usu-ally better, especially if it only means few more minutes deco time.

b. Remember that you and your team mates want to use the same blends.

F. Deep decompression stops1. While there is some anecdotal evidence that suggests a benefit to using deep

decompression stops, more recent scientific studies suggest that there may be no actual benefit.a. A deep stop is a deco stop deeper than required by conventional

decompression models.2. You normally make a deep stop for two minutes at the halfway point

between the bottom depth and the first “required” deco stop, which you find exactly as you find the midpoint for calculating your ascent.a. For example, if you were diving at 45 metres/150 feet and your first

stop is at 12 metres/40 feet, you make a deep stop at 28.5 metres/95 feet.

b. If you make your deep stop on your bottom gas, you typically list the ascent and the deep stop separately (different SAC rates) on the dive planning work slate, though the same depth.

c. You can also calculate ascent based on the midpoints from the bottom to the deep stop, then the deep stop, and then the ascent from the deep stop to the first required stop (three different depths between the bottom and the first required stop) You may do this if you change gases at your deep stop, which affects your oxygen exposure and gas supply requirements.

3. Some desk top deco software will automatically add deep stops if you want. If not, you must enter the deep stop as a way point in the profile it calcu-lates.

4. Dive computers automatically account for deep stops, of course.

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Learning ObjectivesBy the end of this section, you should be able to answer this question:1. What are your two options for conducting deep stops?2. What is the current thinking regarding deep stops?3. What approach to deep stops seems to be the most prudent?

G. More on deep stops1. There are two primary options for conducting deep stops.

a. The first is to use a conventional dissolved gas decompression model and then add deep stops as discussed previously and in the Tec Deep Diver Manual.

b. The second is to use a decompression model that inherently stops you deeper than other models. Most “bubble” models fit into this catego-ry.

2. Although deep stops had a lot of anecdotal support at one time, the current thinking based on US Navy Experimental Diving Unit research is that they may not be as beneficial as once thought.a. The USN compared a bubble model and conventional dissolved gas

model on manned test dives. Dives were to the same depth for the same duration with the same decompression time distributed over a deep stops (bubble) schedule and a conventional (dissolved gas) schedule.

b. The tests were terminated due to an unacceptable DCS rate in sub-jects decompressed with the bubble schedule.

3. Other data are less conclusive.a. Some no stop diving tests find a minor benefit to deep stops.b. Many divers have been using bubble models without difficulties.c. Deep stops and bubble models are common practices widely used in

the tec community, again, without widespread problems.

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4. The prudent approach to deep stops at the moment seems to be:a. Use a conventional dissolved gas model and add deep stops as you

learned. The deep stops will lengthen your shallower stops.b. If you wish to use a decompression bubble model, choose one that is

well supported by human test data.c. Whatever model you use, stay well within limits and pad your

decompression to make it conservative. Don’t be in a hurry to leave your last stop – extend it beyond the required time.

d. Stay up to date on the latest findings in decompression research. Know your sources – just because someone says something on an internet forum doesn’t make it true.

exercise, Other Delivery Content, Tec 45-31. Your two options for deep stops include (choose all that apply)q a. using a deep stops bubble model.q b. adding deep stops to a bubble model.q c. using a conventional dissolved gas model.q d. adding deep stops to a conventional dissolved gas model.2. The current thinking on deep stops isq a. they are unquestionably beneficial.q b. they are unquestionably without benefit.q c. there is some doubt about whether they’re as beneficial as once thought.3. To use deep stops prudently (choose all that apply)q a. use a conventional model, add deep stops and complete the extra deco they add.q b. if you use a bubble model, use one well supported with human test data.q c. use any model conservatively.q d. stay informed about the latest findings in decompression theory.

How did you do?1. a, d. 2. c. 3. a, b, c, d.

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Iv. Decompressing in CurrentsManual Supported Content

Study assignment: Tec Deep Diver Manual, pgs 228-229, Techniques IV, Tec Exercise 5.2

Learning ObjectivesBy the end of this section, you should be able to answer these questions:1. What are some of the procedures and considerations for making decompression dives in a current?2. What is a “drift hang” and what are the advantages and disadvantages?

A. You’ve already learned a lot and practiced regarding tec diving in currents, making stops in them, and emergency procedures. These include:1. Using jon lines2. Using a lift bag/DSMB3. Ascents/descents along anchor or mooring line, and ascents along lift

bag/DSMB line4. Drift kits5. Not staging deco cylinders if there’s a reasonable possibility you won’t

be able to return to them.6. Using swim lines, trail lines, etc., to work a current, just as you would

while recreational divingB. As a review, consider these points:

1. Before making decompression dives in an area with currents, gain expe-rience and be thoroughly familiar with the local techniques by making no stop dives first.

2. It’s easy to overexert yourself trying to out swim a current wearing just recreational equipment; in tec gear it’s even easier. Use your brain, not your back, to work a current.[Review information about currents in the local environment and the techniques used for making deco dives.]

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C. Drift hangs1. It’s often tiring to fight current during a long “hang” (decompression) in mid

water.2. An alternative is a “drift hang” (also called “blue water decompression”) in

which divers decompress along a line from a float or boat while adrift in the current.

3. Procedures vary, but in general:a. All divers return to the mooring/anchor line and start decompression,

maintaining position in the current.b. The boat lowers (or has in place) a weighted line.c. On signal, support divers release the boat from the mooring/ anchor,

and all divers swim to the weighted line while maintaining their stop depth.

d. Divers complete decompression on line.e. A variation is the breakaway hang -- the team releases a line with a

float ball from a mooring or other anchor point. The team decom-presses drifting with the boat, following the float ball.

f. An obvious variation you’ve practiced (or will practice) – the team sends up a lift bag/DSMB and decompresses with the boat following; this may be a planned procedure or the emergency procedure if the team is unable to locate the ascent line/area.

4. Advantagesa. Once adrift, there is no current for practical purposes – it is much

more restful.b. It is easier to maintain stop depth.c. Surface support can easily take unneeded gear (used stage cylinders,

etc.) or bring down extra gas, etc. when not having to fight current.5. Disadvantages

a. Requires close coordination of all teams in the water if all teams will drift together. You often can’t stagger teams going in and coming out. (This isn’t an absolute; in some areas there are ways to stagger teams for drift hangs, but typically it’s not the case.)

b. Waiting for one diver can hold up the drift for several teams -- proce-dures include actions for disoriented divers (usually requires sending up a bag and drifting under it) and accounting for them by surface support.

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c. Surface support is usually mandatory.d. You must account for where you’ll drift. In some environments

with strong current, it’s possible to be pushed into water too shallow for decompression. In other areas, it may be possible to drift into sea lanes with hazardous ship traffic. Plans must account for preventing such problems.

6. As you learned earlier, a drift hang may also be reserved as an emergen-cy procedure if you cannot relocate the ascent line. In that case, you may have no immediate surface support if the boat has to hold station for other teams to complete decompression before coming for you.

Tec 45 Practical ApplicationOn the surface, the practical applications develop skills with procedures related

to gear rigging, using decompression software and dive planning. However, the practi-cal 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.

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 inappropriately. Otherwise, allow teams to develop their own interaction and coopera-tion 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 to develop their capabilities.

At the Tec 45 level, you should see teams that work closely together before, during and after each dive. Even divers who don’t know each other before starting the course should quickly gel into teams that work well together. Unless necessary for logistics or to assure individuals meet performance requirements, avoid breaking up closely-knit, well functioning teams.

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Tec 45 Practical Application OneTec 45 students come into the course with either of two backgrounds. First, they

may have the Tec 40 certification (or a qualifying certification from another organization) that they earned using the minimal Tec 40 equipment configuration. Or, they may have the same certification, but trained in the full standardized technical rig (or sidemount).

The first part of the Tec 45 Practical Application One is primarily for Tec 45 stu-dents who have little or no experience with the standardized technical rig (or sidemount). During this practical application, working in teams, students set up their rigs (including a stage/deco cylinder) following the guidelines in the Equipment I and Equipment II discus-sions of the Tec Deep Diver Manual (or comparable sidemount setup).

If all the students in your class completed the Tec 40 course in the standardized technical rig (or sidemount) and completed Tec 40 Practical Application One following the standards for this practical application, then you may, at your discretion, skip the first part and go directly to the second part (dive planning, discussed below). Alternatively, you may have teams set up their gear to provide you a quick assessment that they have retained what they learned.

If you have a mix of students who did and who did not previously train in the stan-dardized technical rig (or sidemount), it is recommended that you have those experienced with the rig assist those who aren’t in setting up their gear. One method is to assign teams that consist of both types of students.

To 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 members conforms with the standardized technical rigging philosophy previously learned, and with any environment-specific requirements provided by the instructor.2. Working as a team, plan a hypothetical technical dive with a single gas switch made for additional conservatism (not accelerated decompression) and with not fewer than three decompression stops, based on information (gases, depths, times, objective, environment etc.) provided by the instructor, with individual diver gas requirement calculations, turn points, reserves, OTUs, CNS clock, etc. calculated manually (not with deco software) using the TecRec Dive Planning Slate, adequately addressing all points of a Good Divers Main Objective Is To Live planning.3. As a team, compare the resulting calculations with the same dive as calculated by desk top decompression software, find any variations and assess whether these variations reflect minor differences in rounding, etc., or an error in the team’s calculations.

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Part One, Conduct1. Divide the class into teams of two to four individuals.2. Review proper rigging with an already setup kit, including mask, fins,

gauges, exposure suit, deco cylinders, etc. Leave the kit where students can see it, and refer them to the equipment discussion in the first three chap-ters of the Tec Deep Diver Manual, as well as Tec 45 Handout 1.

3. Tell the class that, working as teams, they’re to set up their equipment to the appropriate similar configuration according to your example and what they’ve previously learned.• Depending on logistics, you may give this as an assignment to be com-

pleted by a specific time for your evaluation, or you can conduct this as a session 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 into 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 45 Practical Application I to immediately precede Tec 45 Training Dive One, with time for remediation and adjustments. This gets every-one’s gear set up for the dive, and assures that team mates are familiar with each other’s gear.

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Part Two, Conduct1. Assign each team a Tec 45 level dive to plan using and adequately addressing

all points of A Good Diver’s Main Objective Is To Live dive planning, based on information you provide.

• Tell divers that the intent of this exercise is to plan an entire technical deep decompression dive just as they will as certified Tec 45 divers. Explain that they will be doing this in every practical application session in their training from this point through Tec Trimix Diver.

• You may use this session to meet the planning requirements for Tec 45 Training Dive One, with the same teams, equipment, gases (simulated) etc.

• Have students plan for a mission accounting for equipment, environment and other specifics you provide. Emphasize that this is a team exercise – no one is successful until everyone on the team is successful.

• Give students the dive depth (max 45 metres/145 feet) and time. They should plan the dive as a single gas switch (it is recommended that you assign EANx80 or oxygen as the deco gas) using the deco gas for conservatism. Run the numbers for the depth/time and gases ahead of time to be sure they are planning something realistic for a Tec 45 diver.

• You may provide a decompression schedule, or you may have them generate one using decompression software. However, they must calculate everything else by hand using the TecRec Dive Planning Slate. Encourage team mates to help each other, but not do it for each other.

• They should have their working and deco SAC rates. Assign rates if necessary.• The dive plan should cover all aspects of a Good Diver’s Main Objective Is To

Live.• If divers discover something doesn’t work (e.g., the available cylinders do not

hold enough gas to meet the requirements), they should adjust the plan accord-ingly (for example, reduce bottom time, use a shallower depth, different gear, etc.).

• Give ample time for this exercise. Be available to provide guidance and answer questions.

• When they’re done, review the overall plan and note any additional problems they may not have thought of. Ask them for solutions to these. Different teams may have somewhat different plans – that’s fine, provided they reasonably address all required points.

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2. Have students compare their calculations to those of decompression soft-ware.• Note that because the dive is using gas switches for conservatism, the pro-

file will have to be entered manually (otherwise, the program will acceler-ate decompression, resulting in lower gas requirements, oxygen exposure, etc.

Tec 45 Practical Application TwoTo successfully complete this Practical Application, the student should be able to:1. Calculate the student’s bottom (working) and decompression (resting) SAC rates based on the data gathered during Tec 45 Training Dive One.2. Working as a team, plan a hypothetical technical dive with a single gas switch made for additional conservatism (not accelerated decompression) and with not fewer than three decompression stops, based on information (gases, depths, times, objective, envi-ronment etc.) provided by the instructor, with individual diver gas requirement calcula-tions, turn points, reserves, OTUs, CNS clock, etc. calculated manually (not with deco software) using the TecRec Dive Planning Slate, adequately addressing all points of a Good Divers Main Objective Is To Live planning.3. As a team, compare the resulting calculations with the same dive as calculated by desk top decompression software, find any variations and assess whether these varia-tions reflect minor differences in rounding, etc., or an error in the team’s calculations.

1. Divers calculate their bottom and deco SAC rates based on the informa-tion they acquired during Tec 45 Training Dive One.• Encourage teamwork, but students should determine their SAC rates them-

selves.• Remind students that even though they have their SAC rates from their Tec

40 training, they need to update their SAC rates whenever their equipment changes substantially, and to account for changes in fitness and experience.

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2. Assign each team a Tec 45 level dive to plan using accounting for all steps of the A Good Diver’s Main Objective Is To Live dive planning sequence, based on information you provide.

• Use a different profile from the one provided in Tec 45 Practical Application One. It is recommended you assign the dive that students will simulate. during Tec 45 Training Dive Two. Run the numbers for the depth/time and gases ahead of time to be sure they are planning something realistic for a Tec 45 diver.

• They should plan the dive as a single gas switch (recommended you assign EANx80 or oxygen as the deco gas) using the deco gas for conservatism. See Tec 45 Training Dive Two for specific requirements.

• If the dive is a repetitive dive, remind divers to account for that in their decom-pression planning.

• As before, the intent is for students to plan an entire technical deep decompres-sion dive just as they will as certified Tec 45 divers. They should require less assistance than in the previous practical application.

• Have students plan for a mission accounting for equipment, environment and other specifics you provide. Emphasize that this is a team exercise – no one is successful until everyone on the team is successful.

• It is recommended that you have them generate the decompression schedule with decompression software just as they would when planning the dive without instructor supervision. However, they must calculate everything else by hand using the TecRec Dive Planning Slate. Encourage team mates to help each other, but not do it for each other.

• The dive plan should cover all aspects of a Good Diver’s Main Objective Is To Live.

• If divers discover something doesn’t work (e.g., the available cylinders do not hold enough gas to meet the requirements), they should adjust the plan accord-ingly (for example, reduce bottom time, use a shallower depth, different gear, etc.).


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• Have students write (or print and laminate) the decompression schedule for use during Tec 45 Training Dive Two.

3. Have students compare their calculations to those of decompression software.• Note that because the dive is using gas switches for conservatism, the profile

will have to be entered manually (otherwise, the program will accelerate decompression, resulting in lower gas requirements, oxygen exposure, etc.)

Tec 45 Practical Application ThreeTo successfully complete this Practical Application, the student should be able to:1. Working as a team, plan a hypothetical technical dive with a single gas switch made to accelerate decompression and with not fewer than four decompression stops, based on information (gases, depths, times, objective, environment etc.) provided by the instructor, with individual diver gas requirement calculations, turn points, reserves, OTUs, CNS clock, etc. calculated manually (not with deco software) using the TecRec Dive Planning Slate, adequately addressing all points of a Good Divers Main Objective Is To Live plan-ning.2. As a team, compare the resulting calculations with the same dive as calculated by desk top decompression software, find any variations and assess whether these variations reflect minor differences in rounding, etc., or an error in the team’s calculations.3. Working as a team, plan a single gas decompression dive with a single gas switch made for conservatism using desk top decompression software based on information (gases, depths, times, objective, environment etc.) provided by the instructor, with individ-ual diver gas requirement calculations, turn points, reserves, OTUs, CNS clock, etc., ade-quately addressing all points of a Good Divers Main Objective Is To Live planning.

Tec 45 Practical Application Three has students planning two dives: an accelerat-ed decompression dive using the TecRec Diving Planning Slate (calculated manually), and a single gas decompression dive with a gas switch for conservatism using desk top decompression software. (You may require manual calculation also, at your discretion).

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It is recommended that these dives be the basis for Tec 45 Training Dives Three and Four, respectively. If these dives will not be made concurrently, you may split this practical application into two sessions to make the dive planning part of each dive. You may also have students plan these dives, and then plan entirely different dives in their entirety for each of the training dives.

For both dive plans.

• Encourage teamwork, but students should determine their SAC rates themselves.• If either of these dives will be repetitive dives, remind students to account for

that in their decompression planning1. Assign each team a Tec 45 level dive to plan for an accelerated decompression

dive with four stops, using and adequately addressing all points of A Good Diver’s Main Objective Is To Live planning, based on information you provide.

• Use a different profile from the one provided in Tec 45 Practical Application One or Two. It is recommended you assign the dive that students will simulate. dur-ing Tec 45 Training Dive Three. Run the numbers for the depth/time and gases ahead of time to be sure they are planning something realistic for a Tec 45 diver.

• They should plan the dive as a single gas switch ( assign oxygen as the deco gas for Training Dive Three). See Tec 45 Training Dive Three for specific require-ments.

• As before, the intent is for students to plan an entire technical deep decompres-sion dive just as they will as certified Tec 45 divers. They should require less assistance than in the previous practical application.

• Have students plan for a mission accounting equipment, environment and other specifics you provide. Emphasize that this is a team exercise – no one is success-ful until everyone on the team is successful.

• It is recommended that you have them generate the decompression schedule with decompression software just as they would when planning the dive without instructor supervision. However, they must calculate everything else by handing using the TecRec Dive Planning Slate. Encourage team mates to help each other, but not do it for each other.

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• The dive plan should cover all aspects of a Good Diver’s Main Objective Is To Live.

• If divers discover something doesn’t work (e.g., the available cylinders do not hold enough gas to meet the requirements), they should adjust the plan accordingly (for example, reduce bottom time, shallower depth, different gear).


• When they’re done, review the overall plan and note any additional problems they may not have thought of. Ask them for solutions to these. Different teams may have somewhat different plans – that’s fine, provided they rea-sonably address all required points.

• Have students write (or print and laminate) the decompression schedule for use during Tec 45 Training Dive Three.

2. Have students compare their calculations to those of decompression soft-ware.• Note that because the dive is using gas switches for conservatism, the pro-

file will have to be entered manually (otherwise, the program will accelerate decompression, resulting in lower gas requirements, oxygen exposure, etc.

3. Assign each team a Tec 45 level dive to plan a single gas decompression dive with a gas switch for conservatism that adequately addresses all points of A Good Diver’s Main Objective Is To Live planning, based on information you provide.

• Divers calculate their heavy exercise SAC rates based on the information they acquired during Tec 45 Training Dive Three.

• It is recommended you assign the dive to that students will make during Tec 45 Training Dive Four. Teams should plan the dive for your review.

• They should plan the dive as a single gas switch for conservatism. See Tec 45 Training Dive Three for specific requirements.

• As before, the intent is for students to plan an entire technical deep decom-pression dive just as they will as certified Tec 45 divers. They should require less assistance than in the previous practical application.

• Have students plan for a mission accounting equipment, environment and other specifics you provide. Emphasize that this is a team exercise – no one

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is successful until everyone on the team is successful.• Have them plan the dive with decompression software just as they would when

planning the dive without instructor supervision.• The dive plan should cover all aspects of a Good Diver’s Main Objective Is To

Live.• If divers discover something doesn’t work (e.g., the available cylinders do not

hold enough gas to meet the requirements), they should adjust the plan accord-ingly (for example, reduce bottom time, shallower depth, different gear).

• Give ample time for this. At this point students should be able to do this with lit-tle assistance, but since this will be a real decompression dive (if used for Dive Four), expect students to have some additional questions. Be available to provide guidance and answer questions.


• Have students write (or print and laminate) the decompression schedule for back-up use during Tec 45 Training Dive Four.

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Tec 45 Training Dives

Tec 45 Training Dive OneTec 45 students come into the course with either of two backgrounds. First,

they may have the Tec 40 certification (or a qualifying certification from another orga-nization) that they earned using the minimal Tec 40 equipment configuration. Or, they may have the same certification, but trained in the full standardized technical rig (or sidemount).

Tec 45 Training Dive One repeats many of the skills learned at the Tec 40 level, and builds upon them. The purpose of this dive is:

1. To allow you to assess and as necessary, remediate Tec 40 level skills and over-all diving ability.

2. To acquaint Tec 40 divers who have not previously used the full standardized rig with the performing skills in that rig (or sidemount).

3. To begin developing skills and procedures that students will develop fully in the open water portions of the Tec 45 course.

4. To begin developing skills and procedures that students will fully develop at the Tec 50 level.

Tec 45 Training Dive One is a long dive, but it is quite feasible given the shal-low depths and large gas supplies used. You can expect to progress more quickly with students who are already experienced with the standardized technical rig (or side-mount), whereas plan more time for those who are not.

To successfully complete this training dive, the student must be able to:1. Working in a team, assemble and inspect the standardized technical diving rig (or sidemount) including a stage/deco cylinder following the previously described rigging philosophies and to meet individual/environmental needs.2. Establish proper weighting for the standardized technical rig (or sidemount) and exposure suit as worn in the dive environment.3. Independently don and remove a single deco cylinder at the surface.4. Descend along a line to the bottom, maintaining control of depth and descent speed by adjusting buoyancy.5. Working as a team, perform appropriate bubble checks and descent checks.6. Swim not less than 18 metres/60 feet while sharing gas via long hose as the receiver.7. Swim not less than 18 metres/60 feet while sharing gas via long hose as the donor.

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8. As part of a team, properly stage and secure a deco cylinder on the bottom for later retrieval and use.9. Perform the gas shutdown drill within 60 seconds (40 seconds in sidemount).10. Tow a simulated unresponsive, breathing diver horizontally 6 metres/20 feet underwater.11. As part of a team, retrieve and don a stage decompression cylinder. 12. As part of a team, simulate decompressing on high oxygen EANx/oxygen by ascending to a shallower depth, NO TOX switching to simulated high oxygen EANx/oxygen and com-pleting a stop of not less than five minutes, maintaining physical contact with the line, a wall or the bottom, as needed.13. As part of a team, simulate a descent in rough or choppy conditions by descending to the bottom at a controlled rate in water too deep in which to stand, then conducting a bub-ble check, descent check and an S-drill.14. Perform a working rate SAC swim by swimming for approximately five minutes at a level depth, recording the appropriate information for later calculation.15. In full technical equipment including stage/deco cylinder, demonstrate buoyancy control by establishing neutral buoyancy with the backup buoyancy system and hovering over the bottom for not less than one minute.16. As a team, deploy a lift bag/DSMB from the bottom using the proper technique to avoid entanglement and maintain control of the bag/DSMB.17. 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.18. As a part of a team, 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, and perform four simulated decompression stops for a total of not less than 18 minutes, remaining within .5 metres/1.5 feet of the required stops.19. 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.20. While neutrally buoyant at a simulated decompression stop, perform the gas shutdown drill while maintaining depth within 1 metre/3 feet of the stop depth.21. Record the appropriate information for later calculation of a deco SAC rate by record-ing gas use information during a series of simulated decompression stops.

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22. Throughout the dive, demonstrate time/depth and gas supply awareness by writing the depth and time at each 35 bar/500 psi of back gas consumed.23. 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.24. Throughout the dive, respond appropriately to simulated emergencies prompted by the instructor.

I. Training Dive StandardsA. Tec 45 Training Dive One is conducted in confined water or limited

open water. (See Section Two, Course Standards for definitions of these.) The maximum depth is 10 metres/30 feet. It is a no decom-pression dive. It is recommended that the site provide ready access to water shallow 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 long dive with gas sharing and simulated free

flows. Although it is described as a single dive, it may be appro-priate to break it into two dives.

2. It is recommended that you use as shallow a depth as possible 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 specific 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 in standardized technical rig (or sidemount) as worn when making open water technical decompression dives with Tec 45 limits in the local environment, including exposure suit and stage/decompression cylinder. 1. The ideal is for the instructor to wear the same kit as students.2. If a class has sidemount and backmount configurations, for dem-

onstration purposes it is recommended that both configurations be represented, with the instructor wearing one and a certified assistant wearing the other.

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D. Gas requirements: Students and staff may use air or enriched air, any suit-able blend, in sufficient supply to accomplish the dive performance objec-tives and have free time for experience and practice. It is recommended that the stage/deco cylinder have a richer EANx blend than the back gas cylin-ders, but be breathable to the dive’s maximum depth. You will have students simulate using different EANx blends and pure oxygen.

II. Predive Planning, Briefing and Preparation– suggested sequenceA. 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)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.c. Have students mark their decompression cylinders with the

actual content and max depth, and a simulated content/max depth (example: AIR, 50 METRES, SIM: OXYGEN, 6 METRES)

d. Tell students that they will simulate deep and shallow areas, and handle their simulated deco gas accordingly. [Explain the areas you’ll use as simulated areas.]

e. Students plan the dive based on information you provide (depth, simulated gases, etc.)• Students should have turn pressures, deco schedules,

time limits etc. based on the hypothetical dive.• Tell students they will have to signal you when they

reach any of these limits.• This planning may be the plan developed during Tec

45 Practical Application One (recommended)2. Dive site overview

a. Discuss the 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

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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 require-ment and how you’ll conduct it, including signals you will use, etc.a. proper weighting – no deco cylinderb. don stage/deco cylinder at surfacec. bubble check, descent checkd. out of gas – use long hose as receivere. out of gas – use long hose as donorf. stage deco cylinderg. gas shutdown drillh. unresponsive diver towi. retrieve and don deco cylinderj. ascend to “shallow” depth, NO TOX switch, five min-

ute simulated deco stop (physical contact)k. descent into deep water – bubble check, descent check

and S-drilll. primary BCD failure, neutral buoyancy over bottom

with backup buoyancy systemm. regulator free flow/valve shut downn. SAC swim at constant deptho. deploy lift bag/DSMBp deploy second lift bag/DSMB (spilled bag scenario)q. simulated four stop, neutrally buoyant decompression

(NO TOX gas switch at 3rd stop, total deco time 18 minutes)

r. gas shutdown drill while neutrally buoyant

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s. SAC deco – during simulated decompression stopt. remove stage/deco cylinder in water too deep in which to

stand u. recheck weight with near empty cylindersv. gas/time/depth awareness

4. Review hand signals, emergency protocols, descent and ascent proce-dures, entry and exit procedures and any final detailsa. Predive check – technical level using checklists.b. It’s recommended that you spot check everyone’s gear after it

is donned.

III. Tec 45 Training Dive One – suggested sequenceA. Entry – into water shallow enough 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 cylinders3. Don stage/deco cylinder at the surface4. Bubble check at surface

B. Descent to insensitive bottom (limited open water)1. Students perform descent check; check each other for loose gear,

etc.a. It is recommended that you secretly assign a student to have a

minor gear problem that should get caught by the descent check.

2. Position class for skills.C. Dive skills –instructor demos each as necessary, then has students perform as

briefed.1. Out of gas – long hose gas sharing

a. Instructor chooses a receiver and a donor.b. The team swims 18 metres/60 feet (circle or pattern) sharing

gas via long hose.c. Donor and receiver switch roles.d. Remind students that the receiver leads.

2. Stage decompression cylinder – as a team, students stage and secure

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deco cylinders on the bottom in simulated deep (below the maximum depth for the gas) water, confirming hoses are tucked and valves closed.

3. Gas shutdown drill – within 60 seconds (40 seconds in sidemount)4. Unresponsive diver tow – simulates assisting an unresponsive diver at

deptha. Instructor demonstrates.b. Instructor chooses “victim” and “rescuer.”c. Rescuer establishes neutral buoyancy for self and victim and

then tows horizontally 6 metres/20 feet while holding the vic-tim’s regulator in place and controlling the victim’s buoyancy.

d. Divers switch roles.5. Retrieve and don deco cylinders – teams retrieve and replace their

deco cylindersa. It is recommended that before the dive, you assign a student to

“accidentally” switch immediately after donning.b. Team mates should respond by providing long hose and pulling

deco reg from diver’s mouth (if necessary).c. If team mates don’t catch it, point it out to them.

6. Ascend to “shallow” depth, NO TOX switch, five minute simulated deco stop (physical contact)a. Students ascend as a team, NO TOX gas switch and simulate

five minutes of decompression.b. Physical contact allowed; students may be on a line, against a

wall or on the bottom.c. Remind students of proper positioning.

7. Teams surfacea. If desired/needed, this is a good place for a break, refill cylin-

ders etc.b. From this point, the team will simulate an extended decompres-

sion dive starting with conditions too rough for an adequate bubble check at the surface.

c. Remind students you expect them to carry out routine proce-dures without prompting.

8. Teams descend to bottom in water too deep in which to stand

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a. Divers stay together and control their descents.b. At the bottom, the team conducts a bubble check, a descent

check and carries out S-drills, all divers as donor and receiver.c. Deco cylinders remain on divers.

9. Neutral buoyancy with simulated failed primary BCDa. Completely deflate primary BCD.b. Establish neutral buoyancy with backup system.c. Hover for at least one minute over bottom without kicking

or sculling.d. After exercise, students completely deflate backup BCD sys-

tem and return to primary system.10. Regulator free flow/valve shut down – instructor simulates a free

flow regulator on each diver; the diver switches second stages (if necessary) and shuts down the affected regulatora. Have students return to the primary long hose after the drill

and reopen the valve.b. Confirm the valve is open.

11. SAC swim at constant depth – in teams, divers swim at a constant rate and depth for approximately five minutes recording data for bot-tom SAC calculations.

12. Deploy lift bag/DSMB – within team, one diver deploys a lift bag/DSMB using proper technique to avoid entanglement and to control bag/DSMB

13. Spilled bag scenario, second lift bag/DSMB – team mate sends sec-ond bag/DSMB up the line of the first bag.

14. Simulated four stop, neutrally buoyant decompression with NO TOX gas switch and SAC deco – students ascend the lift bag/DSMB line, reeling in line to designated stop depth.a. Suggested actual stop depth is 1.2 metres/4 feet; in limited

open water, it may be possible to simulate using the last two actual stop depths.

b. Remind students to use neutral buoyancy to remain within .5 metres/1.5 feet of stop depth.

c. To simulate stop depth changes, have students re-descend and then ascend to “next” stop.

d. Students make NO TOX gas switch while maintaining depth;

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team mates may assist each other.e. Students will gather information for later calculation of

deco SAC rate. f. Suggested deco schedule:

Simulated depth time12 m/40 ft 1 min9 m/30 ft 3 min6 m/20 ft 5 min – NO TOX gas switch5 m/15 ft 9 min – SAC deco information and

gas shutdown drillg. After completing decompression, team ascends slowly to

surface in water too deep in which to stand, as they would on a real open water tec dive.

15. Gas shutdown drill – during deco, students control depth using buoyancy only and perform a gas shutdown drill while remain-ing within 1 metre/3 feet of stop depth; no time limit.

16. Students remove deco cylinders and exit (deep water exit rec-ommended).a. If necessary, before exiting, have students recheck their

weight requirements with near empty cylinders and no stage/deco cylinder.

17. Gas/time/depth awareness – assign divers to write down the depth and time for each 35 bar/500 psi of back gas used. Divers should also signal the instructor when the team reaches the turn pressure or time limit that they planned if this were a real decompression dive.

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 hap-pened, mistakes, what worked, what didn’t, what they learned, etc. Comment and fill in missing information as necessary, but have stu-dents critique themselves constructively while you guide the process.

B. Confirm that all divers have their time/depth/pressure information, and their SAC swim and deco data.

C. Divers disassemble and stow equipment.

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D. Students log the dive for your signature.E. Remind students of assignments/tasks before the next scheduled meeting

(knowledge development, etc.)

Tec 45 Training Dive TwoTo successfully complete this training dive, the student must be able to:1. Working in a team, plan a simulated decompression dive with a gas switch for added conservatism based on information (simulated depth, bottom time, gases etc.) provided by the instructor.2. Working in a team, assemble and inspect the standardized technical diving rig (or side-mount) including a stage/deco cylinder following the previously described rigging philoso-phies and to meet individual/environmental needs.3. Independently don and remove a stage/deco cylinder at the surface in water in which it is too deep to stand.4. As part of a team, conduct a bubble check at the surface or just below the surface.5. As part of a team, conduct a descent check on the bottom.6. Underwater, properly stage a stage/deco cylinder for later retrieval and use.7. Perform the gas shutdown drill within 60 seconds (40 in sidemount).8. Swim not less than 18 metres/60 feet with no mask on while sharing gas via long hose as the receiver.9. Respond properly to impromptu emergency drills based on previously learned skills pre-sented by the instructor.10. Underwater, retrieve and don a stage/deco cylinder.11. As part of team, deploy a lift bag/DSMB and ascend along its line conducting a simulat-ed decompression while neutrally buoyant.12. As part of a team while maintaining stop depth during a simulated decompression (plus or minus 1 metre/3 feet) perform a NO TOX gas switch at the first stop at which the gas is breathable (simulated).13. After an interval breathing from a deco cylinder designated by the instructor, or at 20 minutes (whichever is less) during a simulated decompression, conduct an air break, then NO TOX switch back to the deco cylinder and complete the decompression.14. While neutrally buoyant at a simulated decompression stop, perform the gas shutdown

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drill while maintaining depth within 1 metre/3 feet of the stop depth.15. Demonstrate gas/time/depth awareness throughout the dive by a)signaling the instructor and team mates upon reaching the agreed turn point of technical dive plan (not actual dive plan) and b) writing the depth, time and SPG reading at each 12 min-utes throughout the dive.

I. Training Dive StandardsA. Tec 45 Training Dive Two is conducted in open water. The mini-

mum depth is 12 metres/40 feet and the maximum depth is 18 metres/60 feet. It is a no decompression dive that simulates a decompression dive.

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 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 in standardized technical rig (or sidemount) appropriate for the local environment, including exposure suit and stage/decompression cylinder. 1. The ideal is for the instructor to wear the same kit as students.2. If a class has sidemount and backmount configurations, for dem-

onstration purposes it is recommended that both configurations be represented, 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, in sufficient supply to accomplish the dive performance 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, but that all cylinders are breathable to the dive’s maximum depth. You will have students simulate using different EANx blends and pure oxygen.

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1. Students plan a decompression dive within Tec 45 limits using EANx/oxygen for added conservatism based on information you provide (depth, bottom and deco gases, etc.). Tec 45 Practical Application Two may be the planning session this dive.a. Students should have turn pressures, deco schedules, time

limits etc. based on the hypothetical dive.b. Tell students they will have to signal you when they reach any

of these limits.2. Students set up their rigs, but do not yet don exposure suits (gear may

already be set up from the Practical Application)a. Inspect each rig for correct setup, ample gas, proper cylinder



actual content and max depth, and a simulated content/max depth (simulated oxygen recommended, example: AIR, 50 METRES, SIM: OXYGEN, 6 METRES) based on the simu-lated dive.

d. Tell students that they will simulate deep and shallow areas, and handle their simulated deco gas accordingly. [Explain the areas or depths you’ll use as simulated deep and shallow areas; during decompression you can use real depths with simulated gases; for example, air simulated as oxygen -divers should not breath it deeper than 6 metres/20 feet. If the site allows, it is recommended that simulated bottom depth be 30 metres/100 feet or deeper, then have students decompress at the real stop depths, with a switch to simulated oxygen at 6 metres/20 feet.]

e. As appropriate, remind students that the actual bottom time

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may be longer than the simulated bottom time (but with-in no stop limits) if necessary to accomplish all skills.

3. Dive site overviewa. Discuss the 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. Depth/time limits – Students planned a simulated dive; establish the real limits for the dive.


3. Students will need the simulated decompression schedule on their slates, because this is a no stop dive and their dive comput-ers will not provide the schedule.

4. Skill overview – describe each skill, the performance require-ment and how you’ll conduct it, including signals you will use, etc.a. don stage/deco cylinder at surfaceb. bubble checkc. descent checkf. stage deco cylinderg. gas shutdown drillh. no mask, long hose gas sharingi. free time as time allows -- surprisesj. retrieve and don deco cylinderk. deploy lift bag/DSMB and ascentl. simulated neutrally buoyant decompression with NO

TOX gas switchm. air breakn. neutrally buoyant gas shutdown drillo. remove stage/deco cylinder in water too deep to stand

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inp. gas/time/depth awareness

4. Review hand signals, emergency protocols, descent and ascent proce-dures, entry and exit procedures and any final detailsa. Predive check – technical level using checklists.b. It’s recommended that you spot check everyone’s gear after it

is donned.

III. Tec 45 Training Dive Two – suggested sequenceA. Entry – appropriate for environment (no deco cylinder at this point).

1. Divers check their weight (if necessary, no deco cylinder)2. Don stage/deco cylinder at the surface in water too deep in which

to stand 3. Bubble check at surface (just below the surface is acceptable if con-

ditions require)B. Descent to insensitive bottom

1. Students perform descent check; check each other for loose gear, etc.a. It is recommended that you secretly assign a student (to have

a minor gear problem that should get caught by the descent check (a different student and problem from Dive One).

2. Position class for skills.C. Dive skills –instructor demos each as necessary, then has students perform as

briefed.1. Stage deco cylinders

a. Team stages together, confirms valves are closed and cylin-ders secured

2. Gas shutdown drilla. One at a time with each student; 60 seconds (40 with side-

mount)3. No mask, long hose gas sharing

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a. Deploy a line 18 metres/60 feet across clear bottom for students to follow.

b. Designate donor and receiver.c. On your signal, receiver removes mask, signals out-of-

gas. Donor provides long hose.d. After getting settled, divers follow line (receiver leads) to

the end.e. Receiver replaces and clears mask.f. Switch roles and repeat.

4. Free time – surprisesa. Tell students that they will be able to explore the imme-

diate area as teams (set limits as necessary to maintain control) until reaching the required ascent time or gas pressures (actual).

b. You may signal or use a slate to present problems for them to deal with as they’ve trained – anything they’ve learned is fair game.

5. Retrieve and don deco cylinder6. Team deploys a lift bag/DSMB and ascends along the line7. Simulated neutrally buoyant decompression with NO TOX

gas switcha. Students decompress according to the planned schedule.b. Remind students to stay plus or minus .5 metres/1.5 feet

of the stop depth and generally horizontal, stop depth at chest level.

c. Have students NO TOX switch to their simulated EANx/oxygen at the appropriate depth (1 metre/3 feet variation acceptable during switch).

8. Air break

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a. Have students practice switching to back gas for two-three minutes, then NO TOX switching back to deco gas after a set interval using deco gas.

b. Remind students that the typical break is every 20 minutes, but more frequently is acceptable.

c. Remind students that if following a decompression table, break time does not count as deco time.

9. Neutrally buoyant gas shutdown drilla. During the simulated decompression, have students conduct

the gas shutdown drill using only buoyancy control to remain within 1 metre/3 feet of stop depth.

10. Remove stage/deco cylinder in water too deep in which to stand a. After completing the simulated decompression, teams surface

together.b. Remove stage/deco cylinders and exit the water as appropriate

for the environment.11. Gas/time/depth awareness

a. Have students signal you and team mates when they reach an agreed turn point based on the simulated dive plan.

b. Students record the depth, time and SPG reading at each 12 minutes throughout the dive regardless of what else is going on (other than a real emergency). Team mates may assist each other with this task.

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.

B. Confirm that all divers have their time/depth/pressure information.C. Divers disassemble and stow equipment.D. Students log the dive for your signature.E. Remind students of assignments/tasks before the next scheduled meeting


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Tec 45 Training Dive ThreeTo successfully complete this training dive, the student must be able to:1. Working in a team, plan a simulated, accelerated four stop decompression dive (sin-gle gas switch) based on information (simulated depth, bottom time, gases, etc.) pro-vided by the instructor.2. Working in a team, assemble and inspect the standardized technical diving rig (or sidemount) including a stage/deco cylinder, following the previously described rigging philosophies and to meet individual/environmental needs.3. Independently don a stage/deco cylinder at the surface in water too deep in which to stand.4. As part of a team, conduct a bubble check at the surface or just below the surface.5. As part of a team, conduct a descent check on the bottom.6. Perform the gas shutdown drill within 60 seconds (40 in sidemount).7. Swim at an elevated pace for two to four minutes at a level depth, noting time, depth and air pressure information for determining a heavy work SAC rate.8. Respond properly to impromptu emergency drills based on previously learned skills, as presented by the instructor.9. As part of team, deploy a lift bag/DSMB and ascend along its line to the first stop of a simulated accelerated decompression while neutrally buoyant.10. Demonstrate managing a drift decompression using a lift bag/DSMB after primary BCD failure by ascending, establishing neutral buoyancy and beginning a simulated accelerated neutrally buoyant decompression with a deepest stop no shallower than 12 metres/40 feet, then simulating primary BCD failure by switching to the backup buoy-ancy system at 10 metres/30 feet, using the backup buoyancy system for the rest of the dive, including making a NO TOX gas switch to simulated oxygen at 6 metres/20 feet, air breaks, and following the assigned deco schedule while not varying from the stop depths by more than .5 metres/1.5 feet.11. After an interval breathing from a deco cylinder, as designated by the instructor, or at 20 minutes (whichever is less) during a simulated decompression, conduct an air break, then NO TOX switch back to the deco cylinder and complete the decompression.12. During a simulated neutrally buoyant decompression, using the backup buoyancy control system alone, perform the gas shutdown drill without varying from stop depth more than 1 metre/3 feet (no time limit).13. During a simulated neutrally buoyant accelerated decompression dive, simulate switching or actually switch (depending upon gases/computers used) a multigas com-

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puter or computers as appropriate for NO TOX gas switches and air breaks.14. While using the backup buoyancy system to maintain positive buoyancy at the surface, independently remove a stage/deco cylinder in water too deep in which to stand.15. Demonstrate gas/time/depth awareness throughout the dive by a)signaling the instructor and team mates upon reaching the agreed turn point of the technical dive plan (not actual dive plan) and b) writing the depth, time and SPG reading each 15 minutes throughout the dive.

I. Training Dive StandardsA. Tec 45 Training Dive Three is conducted in open water. The minimum

depth is 18 metres/60 feet and the maximum depth is 30 metres/100 feet. It is a no decompression dive that simulates an accelerated decompres-sion dive with at least four stops, with a total simulated decompression time of not less than 18 minutes.

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 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.

C. Students and instructor must be equipped in standardized technical rig (or sidemount) appropriate for local environment, including exposure suit and stage/decompression cylinder. 1. The ideal is for the instructor to wear the same kit as students.2. If a class has sidemount and backmount configurations, for demon-

stration purposes it is recommended that both configurations be rep-resented, 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, in sufficient supply to accomplish the dive performance objec-tives and have free time for experience and practice. It is recommended that the stage/deco cylinder have a richer EANx blend than the back gas cylin-ders, but that all cylinders are breathable to the dive’s maximum depth. You will have students simulate using pure oxygen at 6 metres/20 feet. The NO TOX switch must be at 6 metres/20 feet to meet this dive’s performance requirements.

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1. Students plan a decompression dive with Tec 45 limits using oxygen to accelerate decompression from 6 metres/20 feet to the surface based on information you provide (depth, bottom and deco gases, etc.), with a total simulated decompression time of not less than 18 minutes. Tec 45 Practical Application Three may be the planning session this dive.a. Students should have turn pressures, deco schedules, time

limits etc. based on the hypothetical dive.b. Tell students they will have to signal you when they reach

any of these limits.2. Students set up their rigs, but do not yet don exposure suits (gear

may already be set up from the Practical Application)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.c. Have students mark their decompression cylinders with the

actual content and max depth, and a simulated content/max depth (simulated oxygen, example: EANx36, 28 METRES, SIM: OXYGEN, 6 METRES) based on the simulated dive.

d. Tell students that they will simulate deep and shallow areas, and handle their simulated deco gas accordingly. [Explain the areas or depths you’ll use as simulated deep and shal-low areas; during decompression you can use real depths with simulated gases; for example, air simulated as oxygen, divers should not breath deeper than 6 metres/20 feet. Have students decompress at the real stop depths, with a switch to simulated oxygen at 6 metres/20 feet.]

e. As appropriate, remind students that the actual bottom time may be longer than the simulated bottom time (but within no stop limits) if necessary to accomplish all skills.

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3. Dive site overviewa. Discuss the 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. Depth/time limits – Students planned a simulated dive; establish the real limits for the dive.


3. Students will need the simulated decompression schedule on their slates, because this is a no stop dive and their dive computers will not provide the schedule.

4. Skill overview – describe each skill, the performance requirement and how you’ll conduct it, including signals you will use, etc.a. don stage/deco cylinder at surfaceb. bubble checkc. descent checkd. gas shutdown drille. accelerated SAC swimf. free time as time allows -- surprisesg. deploy lift bag/DSMB and ascenth. begin simulated neutrally buoyant decompressioni. simulated primary BCD failure at 10 metres/30 feet; main-

tain stop depth and switch to backup system for remain-der of dive

j. NO TOX gas switch to simulated oxygen at 6 metres/20 feet

k. switching multigas computersl. air breaksm. neutrally buoyant gas shutdown drill at last stop (5

metres/15 feet or 3 metres/10 feet as planned)n. remove stage/deco cylinder in water too deep in which to

stand

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o. gas/time/depth awareness4. Review hand signals, emergency protocols, descent and ascent pro-

cedures, entry and exit procedures and any final details.a. Predive check – technical level using checklists.b. It’s recommended that you spot check everyone’s gear after it

is donned.

III. Tec 45 Training Dive Three – suggested sequenceA. Entry – appropriate for environment (no deco cylinder at this point).

1. Divers check their weight (if necessary, no deco cylinder).2. Don stage/deco cylinder at the surface in water too deep in which

to stand.3. Bubble check at surface (just below the surface is acceptable if

conditions require)B. Descent to insensitive bottom

1. Students perform descent check; check each other for loose gear, etc.a. It is recommended that you secretly assign a student (to have

a minor gear problem that should get caught by the descent check (different student and problem from Dive One).

2. Position class for skills.C. Dive skills –instructor demos each as necessary, then has students perform

as briefed.1. Gas shutdown drill

a. One at a time with each student; 60 seconds (40 with side-mount)

2. Accelerated SAC swima. Have students swim, in teams, along a pattern at an elevated

rate for two to four minutes recording SAC data.b. Remind students not to overexert – they should swim faster

than they normally would, but not get out of breath.c. The slowest team member sets the pace. d. Remind students that at the slightest indication that they may

be getting out of breath (overexerted), they should stop and rest.

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3. Free time – surprisesa. Tell students that they will be able to explore the immediate

area as teams (set limits as necessary to maintain control) until reaching the required ascent time or gas pressures (actu-al).

b. You may signal or use a slate to present problems for them to deal with as they’ve trained – anything they’ve learned is fair game.

4. The team deploys lift bag/DSMB and ascends along the line, begins simulated neutrally buoyant decompression.

5. Simulated primary BCD failure at 10 metres/30 feet; teams main-tain the stop depth and switch to backup system for remainder of dive.a. Students switch to backup buoyancy system and completely

exhaust the primary system. Students continue to use their backup buoyancy system for all subsequent drills and exercises. The primary system remains connected so it is available in a real emergency.

b. Remind students to stay plus or minus .5 metres/1.5 feet of stop depth and generally horizontal, stop depth at chest level.

c. Deco schedule continues.6. NO TOX gas switch to simulated oxygen at 6 metres/20 feet

a. Students NO TOX switch to simulated oxygen while using their backup buoyancy systems, staying plus or minus .5 metres/1.5 feet of stop depth.

7. Switching multigas computersa. Remind students that this is a simulated accelerated decom-

pression dive, so they must switch their multigas computers whenever they change gases – NO TOX gas switches and air breaks.

b. If possible, students actually switch their computers (for example, they use EANx32 to simulate oxygen; during the dive, they switch their computers to EANx32 when they NO TOX switch at 6 metres/20 feet).

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c. If actually switching isn’t feasible (students using single gas computers or same back gas and deco gas), students simulate switching by pressing their dive computers’ faces. (The intent is to get students in the habit).

8. Air breaksa. Have students practice switching to back gas for two-

three minutes, then NO TOX switching back to deco gas after a set interval using deco gas.

b. Remind students that the typical break is every 20 min-utes, but more frequently is acceptable.

c. Remind students that air break time does not count as deco time when following tables. With multigas comput-ers, switch the computer to switch to air (or EANx used as break gas) during the break.

9. Neutrally buoyant gas shutdown drill at last stop (5 metres/15 feet or 3 metres/10 feet as planned)a. No time limit.b. Plus or minus 1 metre/3 feet of stop depth.

10. Remove stage/deco cylinder in water too deep in which to stand.a. After completing the simulated decompression, teams

surface together and establish positive buoyancy using backup buoyancy control systems

b. Students make an approximately 5 minute “surface safety stop” using only their backup buoyancy sys-tems to remain at the surface

c. Teams remove stage/deco cylinders and exit the water as appropriate for the environment

11. Gas/time/depth awarenessa. Have students signal you and team mates when they

reach an agreed turn point based on the simulated dive plan.

b. Students record the depth, time and SPG reading at each 15 minutes throughout the dive regardless of what else is going on (other than a real emergency). Team mates may assist each other with this task.

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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.

B. Confirm that all divers have their time/depth/pressure information.C. Divers disassemble and stow equipment.D. Students log the dive for your signature.E. Remind students of assignments/tasks before the next scheduled meeting


Tec 45 Training Dive fourTo successfully complete this training dive, the student must be able to:1. Working in a team, plan and execute an actual decompression dive with a single gas switch for added conservatism based on dive site information and limits provided by the instructor and other necessary variables, within Tec 45 limits.2. Working in a team, assemble and inspect the standardized technical diving rig (or side-mount) including a stage/deco cylinder, following the previously described rigging philoso-phies and to meet individual/environmental needs.3. Independently don and remove a stage/deco cylinder at the surface in water too deep in which to stand.4. As part of a team, conduct a bubble check at the surface or just below the surface.5. As part of a team, conduct a descent check on the bottom.6. Perform the gas shutdown drill within 60 seconds (40 in sidemount).7. Demonstrate gas/time/depth awareness throughout the dive by signaling the instructor and team mates upon reaching an agreed turn point of technical dive plan.8. As part of a team, execute the decompression as planned, following a dive computer set for a single gas and/or tables generated with desk top decompression software.9. Properly respond to and deal with any simulated or actual problems that occur during the dive.

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

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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 45 Training Dive Four is conducted in open water. The minimum

depth is 27 metres/90 feet and the maximum depth is 45 metres/145 feet. It is a decompression dive with a single gas switch to provide added conservatism.

B. Ratios – 3 students to 1 instructor, with 1 more student 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.

C. Students and instructor must be equipped in standardized technical rig (or sidemount) appropriate for the local environment, including expo-sure suit and stage/decompression cylinder. 1. The ideal is for the instructor to wear the same kit as students.2. If a class has sidemount and backmount configurations, for demon-

stration purposes it is recommended that both configurations be rep-resented, with the instructor wearing one and a certified assistant wearing the other.

D. Gas requirements: Students and staff may use air, enriched air and/or oxy-gen, in sufficient supply to accomplish the dive performance objectives.


1. Students plan a decompres-sion dive with Tec 45 limits using EANx or oxygen to make decompression more conservative. Tec 45 Practical Application Three may be the planning session this dive.

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a. Students should have turn pressures, deco schedules, time limits etc. for the dive.

b. Tell students this is an actual decompression dive that should be planned and conducted as appropriate and realistic for the local environment.

c. There are no minimum or maximum decompression time requirements, other than being within the normal gas volume, oxygen exposure, etc. Guide students to account for exposure duration.

d. There is no requirement for decompression methodology. It is recommended that students use whatever is standard practice in the local area (drift deco, hanging on a line, deco on the bottom, etc.)

2. Students set up their rigs, but do not yet don exposure suits.a. Inspect each rig for correct setup, ample gas, proper cylinder



actual content and max depth.3. Dive site overview

a. Discuss the 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 overview1. Depth/time limits.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. Even if diving two multigas computers, car-rying a copy of the program-generated deco schedule (or laminated table) is advised for emergency uses. Get them in the habit of doing this for each dive.

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3. Students will use their dive computers for their decompression schedule. Multigas computers may be set for the deco gases to allow accelerated decompression in an emergency, but divers should plan to decompress with them set for bottom gas .

4. Skill/dive overview – describe each skill, the performance requirement and how you’ll conduct it, including signals you will use, etc., as needed.a. don stage/deco cylinder at surfaceb. bubble checkc. descent checkd. gas shutdown drille. gas/time/depth awarenessi. ascent and decompressionj. NO TOX gas switchk. problems

4. Review hand signals, emergency protocols, descent and ascent procedures, entry and exit procedures and any final detailsa. Predive check – technical level using checklists.b. It’s recommended that you spot check everyone’s gear

after it is donned.

III. Tec 45 Training Dive four – suggested se-quence

A. Entry – appropriate for environment (no deco cylinder at this point).1. Divers check their weight (if necessary, no deco

cylinder)2. Don stage/deco cylinder at the surface – as

appropriate for the environment.3. Bubble check at surface (just below the surface

or combined with descent check at bottom is acceptable if conditions require).

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B. Descent 1. Students perform descent check on insensitive bottom; check

each other for loose gear, etc.C. Dive skills – no new skills; there should not be a need to demo.

1. Gas shutdown drilla. One at a time with each student; 45 seconds (30 with side-

mount)2. Tour for fun – surprises/

a. Tell students that they will be able to explore the immediate area as teams (set limits as necessary to maintain control) until reaching the required ascent time or gas pressures (actu-al).

b. You may signal or use a slate to present minor problems for them to deal with as they’ve trained – anything they’ve learned is fair game.

c. However, explain that because this is an actual decompression dive, staged problems will be minimized. A “serious” situa-tion (such as diver with a freeflowing second stage) will be a genuine emergency – they should simply respond as they’ve been trained and abort the dive.

4. Gas/time/depth awareness – students should signal you and their team upon reaching any turn point; everyone is expected to remain within the planned limits

5. Ascent and decompressiona. Technique as appropriate for the local area.b. Contingency situations handled as planned.c. Remind students to use good decompression technique.

6. NO TOX gas switch a. Students NO TOX switch to a higher oxygen EANx, or oxy-

gen, as planned.7. Air breaks

a. Air breaks may not be necessary depending upon the decom-pression duration.

b. You may have students practice switching to back gas for two-three minutes, then NO TOX switching back to deco gas after a set interval using deco gas.

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c. Remind students that air break time does not count as deco time when following tables. Remind students to switch multigas computers to air (or EANx used as break gas) during the break.

8. Remove stage/deco cylinder in water too deep in which to stand.a. After completing the decompression, teams surface

together.b. Teams remove stage/deco cylinders and exit the water as

appropriate for the environment

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 hap-pened, mistakes, what worked, what didn’t, what they learned, etc. Comment and fill in missing information as necessary, but have stu-dents critique themselves constructively while you guide the process.

B. Divers disassemble and stow equipment.C. Students log the dive for your signature.D. Remind students of assignments/tasks before the next scheduled meet-

ing (knowledge development, etc.)

Tec45

Sports

Transcript of Tec45