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  1. 1. Instructor Guide Section four: Tec40 four: Tec 40 Standards and Course Content The Tec 40 subcourse of the DSAT Tec Diver course is a limited, entry-level technical diving program that bridges the gap between recreational diving and full technical deep decom- pression diving. Certified Tec 40 divers are qualified to make limited decompression dives using equipment that is marginally more extensive than that used in mainstream recreational diving. Program Sequence The Tec 40 course consists of three knowledge development sections, three practical applications sessions and four training dives. You will find these in the Knowledge Development, Practical Application and Training Dive subsections, each with content/presenta- tion outlines and related standards. The fully integrated instructional sequence for the Tec 40 course is: Tec 40 Knowledge Development One Tec 40 Practical Application One Tec 40 Training Dive One Tec 40 Knowledge Development Two Tec 40 Practical Application Two Tec 40 Training Dive Two Tec 40 Knowledge Development Three Tec 40 Practical Application Three Tec 40 Exam Tec 40 Training Dive Three Tec 40 Training Dive Four The Tec 40 course provides flexibility in scheduling knowledge development, practical applications and training dives. You may rearrange the sequence and combine knowledge development and practical applications sessions, provided that you maintain the required instructional sequencing. The requirements are: • Any knowledge development sections, practical applications or training dives that precede a training dive in the integrated sequence must be suc- cessfully completed before that training dive. PADI ®padi.com 4-1
  2. 2. Section four: Tec40 Instructor Guide • Any knowledge development sections or practical applications that precede a practical application in the integrated sequence must be suc- cessfully completed before that practical application. • Any knowledge development section that precedes another knowledge development section must be successfully completed before that knowledge development section. For example, the following sequences would be acceptable: Tec 40 Knowledge Development One Tec 40 Knowledge Development Two Tec 40 Practical Application One Tec 40 Practical Application Two Tec 40 Training Dive One Tec 40 Training Dive Two Tec 40 Knowledge Development Three Tec 40 Practical Application Three Tec 40 Exam Tec 40 Training Dive Three Tec 40 Training Dive Four Tec 40 Knowledge Development One Tec 40 Knowledge Development Two Tec 40 Knowledge Development Three Tec 40 Practical Application One Tec 40 Training Dive One Tec 40 Practical Application Two Tec 40 Training Dive Two Tec 40 Exam Tec 40 Practical Application Three Tec 40 Training Dive Three Tec 40 Training Dive Four Special sequence exception for the Tec 40 course: To allow student divers tostart the Tec Diver course immediately (Dive Today), Tec 40 Training Dive One mayprecede Tec 40 Knowledge Development One and Tec 40 Practical Application One.Follow the Dive Today Considerations that accompany Tec 40 Training Dive One. PADI ® 4-2 padi.com
  3. 3. Instructor Guide Section four: Tec40Tec 40 Key Standards Participant prerequisites: Certified as a PADI Advanced Open Water Diver or aqualifying certification from another training organization, PADI Enriched Air Diveror a qualifying certification from another training organization, PADI Deep Diveror proof of 10 dives to 30 metres/100 feet, 18 years old, 30 logged dives (10 withEANx, 7 deeper than 30 metres/100 feet).Instructor qualification: Teaching status, insured (where required) Tec InstructorAssistant qualification: renewed PADI Divemaster or higher certified as a Tec 40 orhigher 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: 2.5 metres/8 feet Maximum 10 metres/30 feet Decompression: No stop only Gases: Air, EANx up to EANx50 Ratios: 6:1, 8:1 with one or more certified assistantsTraining Dive Two Environment: Open water Depths: Minimum: 10 metres/30 feet Maximum: 18 metres/60 feet Decompression: No stop only Gases: Air or EANx up to EANx50. Ratios: 6:1, 8:1 with one or more certified assistantsTraining Dive Three Environment: Open Water Depths: Minimum: 15 metres/50 feet Maximum: 27 metres/90 feet Decompression: No stop only Gases: Air, EANx up to EANx50 Ratios: 4:1, 6:1 with one or more certified assistantsTraining Dive four Environment: Open Water Depths: Minimum: 26 metres/85 feet Maximum: 40 metres/130 feet Decompression: Up to 10 minutes total decompression time based on breathing bottom gas throughout the dive (no accelerated decompression) Gases: Air, EANx up to EANx50 Ratios: 3:1, 4:1 with one or more certified assistants PADI ®padi.com 4-3
  4. 4. Section four: Tec40 Instructor GuideTec 40 Knowledge Development The following knowledge development outlines provide the course content inpresentation form. If the Tec Deep Diver Manual is not available in a language thestudent understands, you may use the outline to present all course content.Otherwise, it is recommended that you cover knowledge development through stu-dent independent study with the manual and handouts, with presentations thatreview/remediate what they studied. The content outlines note manual supported content and other deliverycontent. The manual supported content includes a list of reading, exercise andKnowledge Review assignments (repeated in list form in the Appendix for your con-venience) based upon the Tec Deep Diver Manual. The other delivery content coversmaterial that is not in the Tec Deep Diver Manual. You may simply deliver thismaterial in verbal presentations using the Tec Diver Lesson Guides on PowerPointTM,or (recommended) you can copy those outline sections for students to study inde-pendently along with their assignments in the manual. These sections are in theAppendix ready for copy and handout. Presentations that involve staff introductions,paperwork, logistics, scheduling etc., do not have independent study materials. Tec 40 students do not use the Knowledge Reviews in the Tec Deep DiverManual. Instead, copy the blank Tec 40 Knowledge Reviews in the Appendix fortheir use. You will also find the answer keys there. Students have not completed aKnowledge Development session until they have completed the correspondingKnowledge Review correctly, accurately and completely. The final step in completing Tec 40 Knowledge Development is the Tec 40Exam. Tec 40 students complete the exam after successfully completingKnowledge Development Three. To be successful, the student diver must score80% or higher and review each question missed with the instructor until mas-tery on all questions is achieved. Students who score less than 80% must repeatthe exam (version B) after ample time to remediate. It is recommended that youadminister the exam after Tec 40 Practical Application Three. All material in the Knowledge Development content outline is requiredand must be covered, studied and otherwise remediated until the student dem-onstrates mastery. PADI ® 4-4 padi.com
  5. 5. Instructor Guide Section four: Tec40Tec 40 Knowledge Development one[The voice in these presentations addresses students. Notes to the instructor appear inbrackets.]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 40 course?2. What are your obligations and responsibilities in taking this course?3. What are consequences of failing to meet these obligations and responsibilities?A. Introductions [Encourage a relaxed atmosphere that promotes teamwork.] 1. [Introduce yourself, staff and anyone else involved in the course. Provide a little bit of background and personal information about everyone so stu- dents become acquainted.] 2. [Have students introduce themselves and tell something about themselves, diving interests, etc.] 3. [Collect and review Tec 40 Knowledge Review One.] a. [Review answers to assess mastery so you can tailor your presenta- tions accordingly.]B. Course Goals 1. The goals of the Tec 40 course are a. To qualify you to make limited decompression dives at a level that bridges recreational diving and technical diving. b. To train you in the knowledge, procedures and motorskills required for decompression diving within the limitations of the Tec 40 certi- fication. c. To assure you understand and acknowledge the hazards and risks associated with this level of tec diving, and tec diving in general. d. To train you to prepare for and respond to reasonably foreseeable emergencies that may occur within Tec 40 limits. e. To lay the foundation for continuing your training as a full techni- cal diver in the Tec 45 and Tec 50 courses. PADI ®padi.com 4-5
  6. 6. Section four: Tec40 Instructor GuideC. Your Obligations and Responsibilities 1. During the Tec 40 course, you have these obligations and responsibilities: a. To follow the instructor’s directions and dive plans strictly, and to not separate from the instructor or your dive team. b. To take all aspects of what you’re learning seriously, and display an attitude and conduct that is consistent with that expected of a team-oriented technical diver. c. To refrain from tec diving outside this course until you’re fully qualified and certified. d. To maintain adequate physical and mental health, and to alert the instructor to any problems you have with them. e. To accept the risk for this type of diving, and for specific risks unique to each dive environment, and to immediately notify the instructor if this risk becomes intolerable for you. 2. Failing to meet these obligations and responsibilities can have these con- sequences: a. In the worst case, you could be injured, disabled or killed. b. You will have failed to demonstrate the attitude and maturity required for tec diving, and will not qualify for certification.D. Course Overview, Schedule & Logistics, Administration, Assignments and Study 1. Schedule and logistics [Explain anything that you have yet to cover: the course schedule, required reading and assignment due dates, sessions, and training dives. It’s recommended that you have this printed out and go over it with students when they enroll in the course.] 2. Administration a. Course costs [Explain and collect, as appropriate, all costs associ- ated with the course.] b. Equipment and material requirements [Explain what’s required for the course, and of that, what students must provide and what you will provide.] c. Confirm course prerequisites: • Students may confirm these with certification cards, log entries, signed affidavits, etc. d. Students sign the Tec Diver Statement of Understanding and Learning Agreement [Discuss what the agreement does not cover, such as how you will handle missed sessions/dives, assignments PADI ® not completed, etc.] 4-6 padi.com
  7. 7. Instructor Guide Section four: Tec40 e. Have student divers read, complete and sign the Liability Release and Express Assumption of Risk for Technical Diving (or the technical diving release specified by your PADI Office for your local area). The release must be signed before any inwater train- ing. Tec 40 Training Dive One is the exception if participants sign the standard release used for Discover Tec. f. Have student divers read, complete and sign the PADI Medical Statement. Prior to Training Dive Two, the student must have a physician’s approval and signature on the Medical Statement. If the student received a physician’s approval and signature on a Medical Statement for another course within the last year and has had no medical condition change, and if you have that Medical Statement on file, then the student does not need to see a physician again. g. If students answer “no” to all the medical history questions on the Medical Statement, they may participate in Tec 40 Training Dive One. Note that this applies only to Tec 40 Training Dive One. In some areas, local law requires all scuba participants to obtain a physician’s approval before any diving. h. Diver insurance – It’s recommended that you require students in the DSAT Tec 40 course to have dive accident insurance such as offered by the Divers Alert Network, if available in your area.] 3. Assignments and Study [Brief the class on the following points as appropriate for how you will han- dle knowledge development.] a. You will study independently with the Tec Deep Diver Manual and provided handouts. • The manual supports the entire Tec Diver course – Tec 40 through Tec 50 -- so you’re not required to read all of it at this level. You also won’t be reading it in order. Much of the manual pertains to the next, higher levels of technical diving. • Read the assigned handouts, sections and exercises. b. You will use the manual to complete knowledge reviews provided to you. Do not use the knowledge reviews in the manual. PADI ®padi.com 4-7
  8. 8. Section four: Tec40 Instructor Guide c. We will review the material and help with anything you don’t understand [state where/when: class sessions, practi- cal applications, predive sessions, etc.] d. You will complete the Tec 40 Exam before the last two training dives of the course.II. Technical Diving’s risks and responsibilitiesManual Supported Content Study assignment: Tec Deep Diver Manual, pgs xi, pg xiii Your Obligations and Responsibilities, pg xiv Diver Accident Insurance, pg 1-9 including Tec Exercise 1.1. Disregard Tec Deep and Apprentice Tec Diver Certification Limits discussions. You may skip question 6 in the exercise.Learning ObjectivesBy the end of this section, you should be able to answer these questions:1. How do you define recreational scuba diving and technical scuba diving?2. What is not technical diving?3. What six general risks and hazards does technical diving present that eitherdon’t exist, or aren’t as severe, in recreational diving?4. Why does technical diving, even done “by the book,” pose more risk to youthan recreational diving?5. With respect to risk, what single statement sums up the difference between rec-reational diving and technical diving?6. What risks do you face if you exceed the limits of your training and experience?7. How could a lack of physical fitness affect you as a technical diver?8. What are six characteristics of a responsible technical diver?9. What should you do if you can’t or won’t accept the risks and responsibilitiesdemanded by technical diving?A. Recreational diving and technical diving are both for pleasure, but the terms “recreational diving” and “technical diving” denote important differ- ences in their limits. 1. Recreational scuba diving is defined as no stop diving with air or enriched air to a maximum depth of 40 metres/130 feet, and during penetration dives, within the natural light zone and no more than a total linear distance of 40 metres/130 feet from the surface. PADI ® 4-8 padi.com
  9. 9. Instructor Guide Section four: Tec40 2. Technical scuba diving is diving other than conventional commer- cial or research diving that takes divers beyond recreational diving limits. It is further defined as and includes one or more of the fol- lowing: diving beyond 40 metres/130 feet, required stage decom- pression, diving in an overhead environment beyond 40 linear metres/130 linear feet of the surface, accelerated decompression, and/or the use of variable gas mixtures during the dive. Technical scuba diving uses extensive methodologies, technologies and train- ing to manage added risk. Typically this means using complex equipment in situations where direct access to the surface is inac- cessible due to a ceiling imposed by decompression, or physical barrier such as that found in cave or a wreck diving environments. 3. Technical diving is not simply exceeding the limits of recreational diving. Exceeding recreational limits without the appropriate train- ing, equipment and procedures in place is not technical diving. It is being stupid and irresponsible.B. Technical diving poses risks and hazards that are either not present or not as severe or as likely in recreational diving. These include, but are not limited to: 1. No direct or immediate access to the surface in an emergency due to decompression requirements and/or distance. 2. Hypoxia or hyperoxia leading to unresponsiveness and drowning due to switching to the wrong gas, improper gas choice, or failing to properly analyze the gas. 3. Narcosis leading to poor judgment, bad decisions or slowed responses to emergencies. 4. DCS with severe permanent injury, or death. This can result from higher nitrogen/inert gas loading, improper gas analysis, loss of decompression gas, being forced to surface without completing decompression, improper decompression calculation, personal pre- disposing factors, diving outside the envelope of well documented decompression theory, and other causes. 5. Omitted procedures and errors caused by extensive equipment task overloading, leading to accidents from DCS, gas loss, runaway ascents leading to arterial gas embolism, or barotrauma or oxygen toxicity caused by runaway descents, etc. The need for redundant configurations increases the potential for error. PADI ®padi.com 4-9
  10. 10. Section four: Tec40 Instructor Guide 6. Drowning due to equipment weight and inability to reach the sur- face due to failed BCD.C. Although you’ll learn procedures and equipment application to manage the risks, even when you do everything properly, technical diving poses more risk than recreational diving, because there are more variables, more potential hazards, the error chain leading to an accident is short, and sur- facing in an emergency is (usually) not an option. 1. In recreational diving, if you and your team mate follow all safety rules and procedures as you’ve been taught, the prob- ability of a serious accident is very remote. 2. To sum up the difference between recreational and technical diving risk in a single statement: In techni- cal diving, even if you do everything right, there is still a higher inherent potential for an accident lead- ing to permanent injury and death. You have to accept this risk if you venture into technical diving. 3. However, the vast majority of accidents in technical diving, as in recreational diving, result from failing to apply the proper procedures, failing to have the required equipment and/or failing to have the required prerequisite and/or qualifications for the div- ing being done. 4. Exceeding the limits of your training and experience poses the risks of severe permanent injury, or death, due to an accident. Accidents caused by diving beyond limits usu- ally result from: a. Diver fails to recognize a hazard. b. Diver doesn’t know the procedure that prevents or handles a hazard or emergency. c. Diver has not practiced a procedure and cannot perform it. d. Diver executes a procedure improperly. e. Diver is improperly/inadequately equipped to deal with an emergency. PADI ® 4-10 padi.com
  11. 11. Instructor Guide Section four: Tec40 5. Most divers who had accidents when diving beyond the limits of their training and experience believed, incorrectly, that they could handle the situation.D. Physical fitness and tec diving 1. Technical diving places higher physical demands on you than recre- ational diving. These include, but are not limited to: a. You must wear and transport heavier equipment - predive, climbing a boat ladder, etc. b. You must swim against greater drag, often for extended peri- ods. c. Your body systems must deal with higher nitrogen or other inert gas loads. d. Heavy exposure suits needed for a dive depth/duration may pose predive thermal stress due to overheating, particularly in hot or warm climates. e. Even with exposure protection, dive duration may pose ther- mal stress due to chilling. 2. Physical fitness affects whether you will have the performance and ability needed for technical diving. Like any physical activity, you must be sure a dive is within your physical capability, with sufficient physical reserve to deal with emergencies. Most technical dives call for higher fitness requirements than recreational dives. a. Your cardiovascular system needs to be able to stand thermal stresses, carrying heavy equipment, decompression and have sufficient endurance for high pace swimming against high drag. b. You need sufficient skeletal muscle and bone strength to carry any equipment you need to wear out of the water due to dive logistics (this can vary with the dive). c. Lack of the physical fitness required can affect your safety by limiting your ability to respond to an emergency, or by directly leading to injuries such as a heart attack, heat exhaustion or stroke, broken bones or muscle tears due to falling or strain. d. Only you and your physician can determine your fitness and assess its suitability for different types of diving. It’s your responsibility to dive within the limits of your fitness. PADI ®padi.com 4-11
  12. 12. Section four: Tec40 Instructor GuideE. Six characteristics denote the responsible technical diver: 1. Self-sufficient. The diver plans and executes each dive as though having to handle all emergencies alone, and doesn’t rely on any other diver for safety or knowledge. 2. Team player. The diver is part of the dive team (not just a buddy – more about this shortly), and contributes as a team player on a team effort. 3. Disciplined. The diver doesn’t cut corners, bend rules, disregard dive plans, omit safety equipment or exceed training or equipment limits. 4. Wary. The diver assumes that everything can and will go wrong on a dive, and plans contingencies for when it happens. 5. Physically fit. The diver exercises regularly, eats properly and con- sults a physician regularly to maintain the fitness level required for the specific dives the diver makes. 6. Accepts responsibility. The diver accepts responsibility for person- al safety and accepts and acknowledges the risks and demands of technical diving.F. You can enjoy a lifetime of exciting, adventurous diving without technical diving. 1. Technical diving is not for everyone. It is not a goal for all divers to aspire to. 2. If you cannot or will not accept the responsibilities, risks and demands required by technical diving, then don’t do it. You will only endanger yourself and your fellow divers. PADI ® 4-12 padi.com
  13. 13. Instructor Guide Section four: Tec40other Delivery Content, Tec 40-1 Study assignment: Tec 40 Handout 1Learning ObjectivesBy the end of this section, you should be able to answer these questions:1. How do the Tec 40, Tec 45 and Tec 50 courses fit together as the overall DSAT Tec Divercourse?2. What are the general goals of the Tec 45 and Tec 50 courses?3. What are the limits of your training as a Tec 40 diver?G. The DSAT Tec Diver course 1. The Tec 40 course is the first of three subcourses that together make up the DSAT Tec Diver course. a. The DSAT Tec Diver course was originally called the Tec Deep Diver course (hence the Tec Deep Diver Manual). b. The three subcourses, in order are the Tec 40, Tec 45 and Tec 50 courses. The names reflect the maximum qualification depth in metres for the respective levels. c. Completing all three qualifies you as a Tec 50 diver (formerly Tec Deep Diver), which is a fully qualified, open circuit entry level EANx deep decompression technical diver. 2. Tec 45 general goals are to train certified Tec 40 divers a. to use full technical equipment. b. to make decompression dives to 45 metres/145 feet using air or enriched air, with accelerated decompression techniques. c. to dive with one decompression gas with up to and including 100 per- cent oxygen. 3. Tec 50 general goals are to train certified Tec 45 divers a. to make decompression dives to 50 metres/165 feet using air or enriched air, with accelerated decompression techniques. b. to dive with two decompression gases with up to 100 percent oxygen. PADI ®padi.com 4-13
  14. 14. Section four: Tec40 Instructor GuideH. Certification as a Tec 40 diver qualifies you to dive within the following limits, applying the appropriate procedures and equipment as you’ve been trained: 1. Dive to a maximum depth of 40 metres/130 feet using air or enriched air. 2. Make dives with up to 10 minutes required decompression. 3. Use enriched air nitrox with up to 50 percent oxygen (EANx50) during decompression to make it more conservative. 4. Although your certification qualifies you to these limits, you must also consider other limitations, such as the environment, conditions and other factors, and apply more conservative limits when plan- ning dives. 5. These limits apply, even if you complete the Tec 40 using double cylinders and other equipment required for Tec 45 and above.Exercise, other Delivery Content, Tec 40-11. The Tec Diver course (choose all that apply)o a. consists of three subcourses.o b. begins with the Tec 40 subcourse.o c. no longer exists.2. The Tec 50 course qualifies a diver to make diveso a. with up to 50 minutes decompression.o b. with deco stops as deep as 50 feet/12 metreso c. to a depth of 50 metres/165 feeto d. to a depth of 50 fathoms (300 feet).3. As a Tec 40 diver, applying appropriate procedures and equipment as you’vebeen trained, you’re qualified to (choose all that apply)o a. to dive as deep as 40 metres/130 feet.o b. have up to 10 minutes required decompression.o c. use a single gas with up to 50 percent oxygen during decompression.How did you do?1. a, b. 2. c. 3. a, b, c. PADI ® 4-14 padi.com
  15. 15. Instructor Guide Section four: Tec40II. Tec 40 Equipment requirementsNote to instructor: This section addresses Tec 40 students who will be taking thecourse according to the minimum equipment requirements. Students who willtake the course in the full technical rig (Tec 45 requirements) should com-plete the Equipment study assignments in Tec 45 Knowledge DevelopmentOne.other Delivery Content, Tec 40-2 Study assignment: Tec 40 Handout 2Learning ObjectivesBy the end of this section, you should be able to answer these questions:1. Why can the equipment requirements for Tec 40 be less stringent than the stan-dardized technical rig?2. What are the guidelines for selecting masks, fins and snorkels for the Tec 40level?3. What characteristics do you look for cylinders and cylinder valves for the Tec40 kit?4. What is the minimum number of fully independent regulators, per diver, andhow do you configure each?5. What type of BCDs can you use for Tec 40 level diving? Why is a tec divingharness recommended?6. How do you choose an appropriate exposure suit for technical diving?7. What are your options regarding weight systems, and what are the advantagesand disadvantages of each?8. What types of dive computers and other instruments do you need for Tec 40level diving?9. What types of cutting tools are appropriate for deep technical diving, and howmany should you have?10. What are six general guidelines regarding pockets, accessories and clips youmight need when technical diving?11. What is a “stage/deco cylinder”?12. How do you set up a stage/deco cylinder?13. Why might you need a lift bag/DSMB and reel on a technical dive? PADI ®padi.com 4-15
  16. 16. Section four: Tec40 Instructor Guide14. What are suitable lift bags/DSMBs and reels, and how do you secure them on yourrig?15. What are four recommendations regarding equipment maintenance?You should also be able to:16. Describe the layout, arrangement and configuration of the basic Tec 40 rig, withoptions, from head to toe as worn by a Tec 40 diver.A. Tec 40 equipment requirements and the standardized technical rig 1. The technical diving community has a generally accepted open circuit equipment configuration as worn on a technical deep dive. This standard- ized technical rig employs all required equipment in a streamlined config- uration based on a philosophy that minimizes confusion and procedural error. The standard technical rig (backmount or sidemount) is required at the Tec 45 level and beyond. 2. You can dive with a less stringent equipment configuration (i.e. the Tec 40 kit or rig) within Tec 40 limits because the depth and decompression time limits are very restricted compared to broader technical deep diving. a. Exceeding Tec 40 limits (40 metres/130 feet and up to 10 minutes total required decompression) is not acceptable or reasonable with the Tec 40 rig.B. Mask, fins and snorkel 1. Generally, the mask and fins you use for recreational scuba diving in a given environment are acceptable for the Tec 40 rig. a. Full sized fins (appropriate to your size) are generally recommend- ed. b. Secure/tape loose straps so they don’t dangle and can’t slip. c. Spring heel fins (in place of straps) are good options because they’re very strong, nothing dangles and they don’t need adjust- ment and are easy to don and remove. 2. Snorkels are optional, but generally recommended for the Tec 40 rig. a. They allow you to breathe at the surface without using gas from your cylinder. b. They can be slightly cumbersome in an air sharing situation, so you may want to carry a folding/collapsible model in your pocket. PADI ® 4-16 padi.com
  17. 17. Instructor Guide Section four: Tec40C. Cylinders and valves 1. You generally want a high capacity cylinder as your primary cylin- der with the Tec 40 kit. This is because you use more gas on a deeper dive, and you need to keep a larger reserve. 2. 11-12 litre/71.2-80 cubic foot cylinders are generally considered the minimum size – larger (18 litre/100 cubic foot+ ) cylinders are preferred, but not readily available in some locations. a. If you opt for double cylinders, you should wear the stan- dardized technical rig, not the Tec 40 kit. 3. The cylinder should have an H or Y valve, which allows you to have two entirely separate regulators. In case of a failure, you can shut down the gas to either one and still access the remaining gas with the other. a. With Tec 40 limits, it is alternatively acceptable to have a large, main cylinder with a pony bottle in place of an H/Y valve. b. If you use a pony instead of an H/Y valve, it should have a capacity of 850 litres free gas/30 cf or larger. c. The pony usually has the same gas (EANx blend or air) as the main cylinder. If it has a higher oxygen content, the gas must still be breathable at the deepest planned depth (max 1.4 ata/bar), with a margin for error. 4. The DIN (Deutche Industrie Norm) threaded system for valve apertures is generally preferred to the yoke system in tec diving. 5. Valve caps should not be tied to valves as they commonly are in recreational diving. Remove completely when diving.D. Regulators 1. Because you cannot immediately surface, tec diving always requires a minimum of two fully independent regulators per diver (does not count those on stage or decompression cylinders). 2. Choose top of the line, balanced regulators for maximum reliabili- ty and performance at depth. 3. Configure the regulator that goes on the right valve post with a low pressure inflator hose and second stage with a two metre/seven foot hose. PADI ®padi.com 4-17
  18. 18. Section four: Tec40 Instructor Guide 4. Configure the regulator that goes on the left valve post with the SPG and a second stage on a standard length hose (about 80 cm/32 inches). If using a dry suit or a double bladder BCD system, this regulator also has a low pressure inflator hose. a. If using a pony bottle instead of an H valve, both regulators have SPGs. In this case, the SPGs must be clearly marked or secured to avoid any confusion. 5. Neither regulator has two second stages. 6. The DIN connection system is preferred (most DIN regulators accept adapters for yoke use).E. BCD and harness 1. Most BCDs with shoulder and hip D-rings (other suitable attachment hardware in those locations) can be used for a Tec 40 rig. The D-rings are necessary for your decompression cylinder. 2. A tec diving harness configured for a single cylinder is generally recom- mended, though not essential, for the Tec 40 kit. a. Tec harnesses are harnesses that mount on top of an interchange- able BCD bladder. There are rigid plate (steel, aluminum or plas- tic) and all fabric versions. b. Tec harnesses have crotch straps, adjustable shoulder and waist D-rings and other features suited to higher level tec diving. c. The tec harness is recommended because you will use it when you move on to the Tec 45 course, and because you can use a double bladder BCD (BCD with two independent bladders and inflation/deflation systems) so you have backup buoyancy con- trol. • In a decompression situation, simply dropping weights to restore buoyancy may not be an option because you would have too much buoyancy to maintain a decom- pression stop. • Planning for BCD failure must be part of planning any technical dive. The double bladder BCD is the simplest, most reliable option. • The Tec 40 rig (single cylinder) is not as negatively buoyant as higher level tec rigs, so redundant buoyancy is not mandatory at this level. PADI ® 4-18 padi.com
  19. 19. Instructor Guide Section four: Tec40F. Exposure suits 1. Choose your exposure suit based on the water temperature at depth and the dive duration. 2. Tec dives tend to be longer than recreational dives, calling for more exposure protection. You also don’t exert and generate much heat while decompressing. 3. Dry suits offer the longest durations and coldest water protection. a. They may provide ample backup buoyancy. b. You should master dry suit diving as a recreational diver before using a dry suit for technical dives. • 20 dry suit dives is a conservative minimum before tec diving dry. • In recreational diving, you only use your dry suit for buoyancy control while underwater. • In tec diving, you typically add gas to the suit to avoid a suit squeeze and use your BCD. This means controlling the gas in both your suit and BCD – a more complex skill to master. 4. Wet suits are adequate in warmer waters and well suited to dives within Tec 40 limits. a. A full 6 mm/.25 in wet suit with hood will generally handle dives up to two or three hours (far longer than a Tec 40 dive) in water 24ºC/75ºF or warmer. b. In a heavy rig, you need a double bladder BCD or other means for reliably handling a BCD failure. c. The advantage of a wet suit over a dry suit is operational simplicity – you only need to adjust your BCD.G. Weight systems 1. Except in very warm water requiring minimal exposure protection, you will usually need weights even in a technical rig. A weight belt, integrated weights or a weight harness are acceptable. a. Some tec divers choose a metal plate harness to reduce the amount of lead they need to wear. PADI ®padi.com 4-19
  20. 20. Section four: Tec40 Instructor Guide 2. Weight belt a. Advantages: simple, readily available when needed b. Disadvantages: with crotch strap, must don after putting on rig so it’s not trapped. 3. Integrated weights a. Advantages: no need to put on last, positioned amid rig b. Disadvantages: must have BCD/harness system with weight system build in; makes overall scuba rig heavier 4. Weight harness a. Advantages: put on before scuba rig, doesn’t add to rig’s weight. b. Disadvantages: may be awkward to adjust rig so it doesn’t interfere with quick release weight ditching. 5. Loss of weights can be significant hazard on a decompression dive because it can make it difficult or impossible to stay at stop depth. a. Some tec divers put two quick release buckles on weight belts to avoid accidental loss. b. Another option is to wear a crotch strap over a weight belt to avoid accidental loss. With this approach, it’s recom- mended that the crotch strap have a quick release so the weights can be discarded if necessary.H. Instrumentation 1. You need two ways of determining your decompression require- ments. a. The simplest option is to wear two dive computers. b. The second option is to wear a computer with depth gauge, timer and decompression tables. 2. For Tec 40, you only need a standard air dive computer or comput- ers. a. An EANx compatible computer is recommended – allows you to benefit from more bottom time with enriched air, and calculates your oxygen exposure. b. If you have yet to invest in your dive computers, choose models that run multiple gases and trimix so you’ll be set for Tec 45 and beyond. PADI ® 4-20 padi.com
  21. 21. Instructor Guide Section four: Tec40 3. Arm mounted instruments (other than SPG) are generally preferred (required at the Tec 45 level and up). 4. Mechanical SPGs are generally preferred because they’re simple and reli- able. 5. Compass – You need a high quality, liquid filled model if using a standard compass. Many newer dive computers have electronic compasses. The compass is commonly carried in a pouch or pocket until needed.I. Cutting tools 1. You should have a cutting tool, and ideally two (two required at Tec 45 level up). Mount at least one where you can reach it with either hand (generally waist/chest area). 2. Typical dive knife, dive shears, Z-knife (hook with blade), stainless fold- ing knives and dive tools are all acceptable. 3. Large, calf-mounted knives/tools are generally avoided in tec diving, espe- cially cave diving and wreck penetration, because they entangle easily.J. Guidelines for pockets, accessories and clips 1. Avoid large pocket pouches on harnesses – they cause too much bulk and clutter. 2. Most useful pockets in tec diving are thigh pockets on your exposure suit. 3. Mount stainless steel or brass clips on accessories to clip to your BCD or harness. Don’t mount the clips on the BCD or harness. 4. Sliding gate clips (a.k.a. dog clips) are preferred to marine snaps (swing- ing gate clips), because they won’t accidentally clip to things by them- selves. 5. Choose clips based on the environment – you need larger clips when wearing thick gloves. 6. Using and mounting clips a. When possible, keep accessories in pockets until needed. b. Clip accessories well out of the way, secured so they don’t dangle. c. Attach clips so they can break away so you can release in an emer- gency. The simplest approach is to mount the clip via a small PADI ®padi.com 4-21
  22. 22. Section four: Tec40 Instructor Guide o-ring or thin pull tie that breaks with a sharp tug.K. Stage/deco cylinders 1. A stage cylinder is used to extend the deep portion of the dive. A deco (decompression) cylinder provides gas (usually with higher oxygen content) during decompression. They are rigged the same, so it’s common to call deco cylinders “stages” or “stage cylinders.” The general term for both is “stage/deco cylinder.” In context, the terms are seldom confusing. 2. Stage/deco cylinders are worn on the side under the arm, clipped at the waist and on the chest. 3. A stage/deco cylinder never replaces one of the two regulators/ valves you need from your primary gas supply. 4. As a Tec 40 diver, you will often use a deco cylinder. a. Some dives at this level do not need a deco cylinder, because you have enough gas, plus your required reserve, for the entire dive including decompression. b. But, a deco cylinder is recommended nonetheless because it provides extra gas capacity, plus gives you the option of switching to EANx with a higher oxygen content for added decompression conservatism. (More about this later). 5. Typical stage/deco cylinder setup a. The cylinder is typically a 4 litre/30 cf size or larger. The popular aluminum 11 litre/80 cf has more capacity than you usually need at the Tec 40 level, but it is commonly avail- able and easy to handle. It is perfectly acceptable to use – having too much gas is seldom an issue. b. The cylinder has a nylon rope/strap approximately 46 cm/18 in, approximately under the valve opening, running down to a band around the cylinder with a clip at each end. This serves as a handling strap; the clips attach the cylinder on your BCD D-rings at the waist and chest/shoulder. c. The regulator has a single second stage and SPG. Hoses tuck under inner tubing, bungee or stretch nylon straps around cylinder. d. The second stage has break-away clip usually attached to PADI ® 4-22 padi.com
  23. 23. Instructor Guide Section four: Tec40 the hose close to where it meets the second stage. e. The SPG may have a very short hose, or a standard length hose that is tucked along the cylinder length. f. It’s recommended that the clips be attached via rope or nylon so you can cut the cylinder free if a clip jams. g. For safety, stage/deco cylinders are always clearly marked with the gas blend they contain, the maximum depth you can breathe the gas (based on the oxygen partial pressure) and the diver’s name. These markings are always large and positioned so a team mate can read them while the cylinder is worn.L. Lift bags/DSMBs (Delayed Surface Marker Buoys) and reels 1. You may find yourself accidentally away from your planned ascent line (anchor/mooring line). 2. In this case, your team uses a reel to deploy a lift bag or DSMB. This gives you an ascent reference, allows surface support person- nel to track your position, and helps you maintain your decompres- sion stop in midwater. 3. Suitable lift bags are brightly colored, with large capacities (45 kg/100 lbs lift) preferred. DSMBs are taller and more compact; they don’t have to have the same lift capacities. Preferred DSMBs have one-way valves for filling, with overpressure valves. These keep the buoy inflated even if it topples at the surface momentari- ly. It is recommended that you write your name on your lift bag/ DSMB for surface support identification. 4. Lift bags are carried rolled up and tucked into special carrying pockets or put in bungees that stow them horizontally in the small of the back. DSMBs roll up more compactly, generally, and fit in harness/BCD pockets or thigh pockets. 5. A suitable reel is compact with ample line to reach the surface. PADI ®padi.com 4-23
  24. 24. Section four: Tec40 Instructor Guide 6. The reel is clipped to a D-ring on the right hip.M. Maintenance 1. You rely on your gear for life support. Therefore, maintain it according to manufacturer recommendations. 2. Have regulators, valves, BCDs and gauges inspected and over- hauled at least annually, or more frequently for heavy use or as manufacturer specified. 3. Have anything that doesn’t appear to work normally serviced before using it. 4. Never tec dive with gear in anything but top shape and within its design parameters. To do otherwise needlessly raises your risk of injury or death by starting the dive with a potential problem.N. Putting it together: basic Tec 40 rig, head to toe 1. Use a cylinder with H or Y valve in a BCD/tec harness. 2. The left side regulator has a short hose second stage. This is the secondary regulator. It routes to the right and hangs below the chin on a bungee. The SPG hose goes down along the cylinder; the SPG has a clip to secure it to waist or chest D-ring (as preferred). Low pressure hose(s) feeds the dry suit and/or backup BCD (if used). The valve is open all the way (do not close it back a quarter turn). 3. The right side regulator has a long hose second stage. This is the primary regulator. It is the last thing you put in place when kitting up. The hose routes straight down along the cylinder to the hip, then up across the chest and around the left side of the neck into the mouth. At the hip, the safety reel lies on top of it to help keep it in place. The low pressure hose feeds the primary BCD inflator. There is no SPG. The valve is open all the way (do not close it back a quarter turn). 4. If using a pony instead of an H/Y valve, the pony goes on the left side of the main cylinder and takes the left side (secondary) regula- tor. In this case, the right (primary) regulator has the primary SPG, which is clipped as described above. The pony/secondary SPG is clipped low and behind the diver, where it is retrievable but not easily confused with the primary. It is also clearly marked (label, PADI ® 4-24 padi.com
  25. 25. Instructor Guide Section four: Tec40 color, etc.) to easily distinguish it from the primary SPG. 5. With double bladder BCDs, the backup inflator is secured behind the diver so that it is easy to deploy, but not easily confused with the primary (you only use one BCD bladder at a time). a. Some divers leave the LP hose disconnected from, but bun- geed to the backup inflator. This avoids accidental inflation (leaking inflator valve), but is easily connected for use. 6. Instruments are ideally arm mounted (except SPG), though com- pact consoles are acceptable in the Tec 40 rig. 7. The weight system is secure, free for ditching. The backup buckle is secured if used. 8. Mask and fins are preadjusted and inspected, secured so they can’t slip out of adjustment.Exercise, Other Delivery Content, Tec 40-21. Tec 40 has less stringent equipment requirements than the standardized techni-cal rig, because the limits of Tec 40 diving keep you within recreational depthlimits and a relatively short decompression time.o Trueo False2. You cannot use the same fins you use in recreational diving for Tec 40 diving.o Trueo False3. The recommended valve type for the Tec 40 kit iso a. the standard yoke valve.o b. a J reserve valve.o c. an H or Y valve, DIN system.o d. a J or K valve, yoke system.4. The minimum number of fully independent regulators, per diver, iso a. 1o b. 2o c. 3o d. 6 PADI ®padi.com 4-25
  26. 26. Section four: Tec40 Instructor Guide5. You can use any BCD with D-rings or attachment hardware at the shoulder/waist for the Tec 40 kit.o Trueo False6. Choose an exposure suit for a tec dive based on __________. (choose all thatapply)o a. deptho b. durationo c. temperatureo d. activity level7. You never use a weight belt while tec diving.o Trueo False8. For the Tec 40 level, a single computer is all the instrumentation you need.o Trueo False9. At the Tec 40 level, you should have at least one cutting tool, but it’s recom-mended you have two.o Trueo False10. General guidelines regarding pockets, accessories and clips include (check allthat apply):o a. mount clips to the accessories.o b. attach clips so they can break away.o c. thigh pockets on your exposure suit are a good option.o d. marine (swing gate) clips are the best choice.11. At the Tec 40 level, a stage/deco cylinder will be used too a. carry a decompression gas.o b. carry gas to extend the deepest portion of the dive.o c. both a or b.o d. None of the above. PADI ® 4-26 padi.com
  27. 27. Instructor Guide Section four: Tec4012. A stage/deco cylinder is always marked with the gas it has in it, the maximum depthand the diver’s name.o Trueo False13. You may need a lift bag/DSMB and reelo a. as a backup BCD.o b. in case you lose track of your ascent point.o c. to open a shipwreck hatch14. A suitable lift bag or DSMB should have ample lift and be blue or gray.o Trueo False15. Never, ever tec dive with gear that’s in anything less than top shape.o Trueo False16. The primary regulator (choose all that apply)o a. goes on the right.o b. has a long hose second stage.o c. has the primary BCD low pressure hose.o d. goes on the left.How did you do?1. True. 2. False. The same fins you use recreational diving are usually suitable for theTec 40 level. 3. c. 4. b. 5. True. 6. a, b, c, d. 7. False. A weight belt is a common optionin tec diving. 8. False. You need at least two computers, or one computer and a depthgauge, timer and decompression tables. You should also have SPGs and a compass. 9.True. 10. a, b, c. 11. a. 12. True. 13. b. 14. False. It should be red, yellow or some otherbright color. 15. True. 16. a, b, c. PADI ®padi.com 4-27
  28. 28. Section four: Tec40 Instructor GuideManual Supported Content Study assignment: Tec Deep Diver Manual, pgs 84-87, Oxygen Compatibility Review, Manufacturer Warranties and Hyperoxic GasesLearning ObjectivesBy the end of this section, you should be able to answer these questions:1. What are the guidelines regarding material and equipment compatibility using enrichedair with more than 40 percent oxygen?O. Oxygen compatibility review 1. As you recall from your Enriched Air Diver course, using gas blends with more than 21 percent oxygen calls for special equipment considerations to avoid fire and/or explosion hazards. a. As a Tec 40 diver, you will be qualified to use EANx up to and including 50 percent oxygen – the higher the oxygen content, the more important this issue is. 2. Any equipment (regulator, valve, cylinder) that will be exposed to a gas with more than 40 percent oxygen, or pure oxygen, at any time (including during blending) must be rated for oxygen service. a. It must be oxygen clean – free of contaminants. b. It must be oxygen compatible – made from materials that don’t combust easily in oxygen. 3. Follow manufacturer recommendations regarding use with air, enriched air or oxygen. Some manufacturers require oxygen service for any enriched air, and some limit the oxygen percentage. However, you may have to make some compromises. [Provide updated information on the oxygen compatibility issue as available.] [See Note to Students.] 4. If you expose oxygen service equipment to nonoxygen clean gases or other contaminants, the equipment is no longer oxygen clean or oxygen service rated. a. Example: Using an oxygen service regulator on a standard air cylin- der – the regulator is considered contaminated. b. Example: Filling an oxygen service cylinder from a standard scuba air source – standard scuba air (Grade E) is not oxygen clean, and the cylinder must then be re oxygen cleaned. (In the U.S. you must PADI ® 4-28 padi.com
  29. 29. Instructor Guide Section four: Tec40 use Grade E Modified or Grade J). 5. Leave enriched air cylinder tags in place for removal by blender – this allows blender to confirm that the cylinder was not refilled by nonoxygen clean air source. 6. To minimize the heat of compression, open cylinder valves slowly and allow equipment to pressurize slowly when using enriched air and oxygen. 7. Protect oxygen service equipment from contamination by keeping it bagged and sealed from the environment until needed. Rinse and stow oxygen service equip- ment as soon as possible after use, and keep it away from areas or exhaust that may have oil or other contamination. 8. The general guideline is to have oxygen service equipment recleaned annually. 9. Violating guidelines regarding oxygen compatibility carries a severe risk of injury and/or property damage caused by fire and/or explosion.Note to Students: [Read this to student divers if the DSAT Tec Deep Diver Manual is not in a languagethey can understand.[ You’re learning to use enriched air nitrox with more than 40 percent oxygen and/or pureoxygen to extend no stop time and benefit decompression. Their use verges on the essential fordecompression after long, deep dives. The use of higher oxygen probably lessens the risk of de-compression sickness, because it is generally believed that for a given a decompression model, aschedule requiring shorter stops is more reliable than a schedule requiring longer stops. Withoutthe high oxygen, you’d face impractically long decompression stops. Therefore, when a diver canget out of the water quicker (accelerated decompression), it reduces the exposure to others risks asdiverse as marine predators, hypothermia, getting separated from the boat in strong currents, andso on. Technical diving is undoubtedly safer with the use of high oxygen gases than it would bewithout them, which is why it is a standard practice in the tec diving community. Using hyperoxicgases, however, is not without some risk and controversy. Outside of issues you’ve learned relatedto central nervous system and pulmonary oxygen toxicity, the greatest hazard comes from the riskof fire. That’s why, as you’ve learned, any high pressure device coming in contact with a gas withmore than 40 percent oxygen (or less than 40 percent if specified by the manufacturer) must becleaned and dedicated for use with pure oxygen. That’s easy to say, but not as easily done.At this writing, relatively few equipment manufacturers in the dive industry warrant the use of anyof their equipment with pure oxygen. A few do, but others specifically warn against using theirequipment with enriched air nitrox mixtures containing greater than 40 percent oxygen. Yet, youwill still learn in this course to use proper oxygen service equipment with hyperoxic gases includ-ing pure oxygen. PADI ®padi.com 4-29
  30. 30. Section four: Tec40 Instructor GuideBasically it comes down to balancing the risks: the risk of getting seriously hurt orkilled due to decompression sickness against the risk of getting seriously hurt orkilled due to fire or explosion. Most tec divers believe – and accident data sup-port – that provided you’re using properly cleaned and compatible equipment, notusing oxygen is a far greater risk than using it. In fact, while plenty of divers havebeen bent over the years, as of this writing only a handful – perhaps only one ortwo -- has been seriously injured as a result of an oxygen fire using a hyperoxicgas in a technical scuba diving context. And, that is in the context of tens of thou-sands of dives (at least) made with such mixtures over the past decade.In the end the choice will be yours. If you decide to stick with the strict manufac-turer’s guidelines for your regulators, tanks, valves, and SPGs, you may have tochoose decompression gases with no more than 40 percent oxygen. But if so, youmust then be willing to accept the risks attendant to the lengthier decompressiontimes involved. Most of the technical diving community believes that, the manufacturers’warnings notwithstanding, you are better off in technical diving to use oxygen andother hyperoxic mixes than not. The risk of fire and explosion is real and is, yetagain, another risk you must personally assume before getting involved in techni-cal diving. To manage and minimize that risk, be certain that any equipment youwill use with a gas with more than 40 percent oxygen has been serviced for thatuse by a qualified professional.III. Gas Planning – EAD review, oxygen limits, SAC and gassupply requirements, oxygen toxicity and exposureManual Supported Content Study assignment: Tec Deep Diver Manual, pgs 35-50, Gas Planning I, Tec Exercise 1.3Learning ObjectivesBy the end of this section, you should be able to answer these questions:1. What is an Equivalent Air Depth (EAD) and how do you find it?2. What are the maximum recommended oxygen partial pressures for deep techni-cal diving?3. What determines the maximum depth to which you can use an enriched airblend during the working (bottom) phase of the dive?4. What determines the maximum depth to which you can use an enriched airblend during the decompression/safety stop phase of a dive? PADI ® 4-30 padi.com
  31. 31. Instructor Guide Section four: Tec405. How do you find your Surface Air Consumption (SAC) rate?6. How do you use your SAC rate to estimate your gas supply requirementsfor a given depth and time?7. How do you determine your reserve gas supply ?8. How do you determine how much gas a cylinder has?9. What are CNS oxygen toxicity and pulmonary oxygen toxicity, and what causes each?10. What are the signs and symptoms of CNS oxygen toxicity?11. What are the signs and symptoms of pulmonary oxygen toxicity?12. What is the so-called “CNS clock”?13. What are Oxygen Tolerance Units (OTUs)?14. What methods do you use for managing oxygen exposure?15. What is the primary way you avoid CNS oxygen toxicity while divingwith air, enriched air or pure oxygen?A. Equivalent Air Depth (EAD) 1. As you recall, the EAD is an adjusted depth on air tables when diving with EANx. 2. EANx has less nitrogen than air; therefore the EAD is less than the actual depth. 3. You find the EAD by: a. using formulas [write out for students] b. Looking it up on tables such as the DSAT Equivalent Air Depth Table or the Equivalent Air Depth and Oxygen Management Table found in the Tec Deep Diver Manual Appendix. Remember to express the frac- tion of oxygen as a decimal; e.g. 32% oxygen, use .32. PADI ®padi.com 4-31
  32. 32. Section four: Tec40 Instructor Guide c. Using desk top decompression software like you’ll be applying in this course. [Intro this only – software will be covered in more detail later.] [With the class, use tables or formulas to find several EADs for depths to 40 metres/130 feet using various blends. This is primarily a review/update from recreational enriched air training.] 4. Enriched air dive computers automatically determine EADs in their calculations.B. Maximum depth 1. As you recall, in recreational enriched air diving, the maximum oxygen partial pressure (PO2) is 1.4 ata/bar. 2. Technical diving uses the same limit for the bottom or working part of dive. a. The maximum depth to which you can use an EANx blend or oxygen added during the decompression phase comes from the depth at which you reach a PO2 of 1.6 ata/bar (contingency maximum in recreational enriched air div- ing). b. Limiting your PO2 to a more conservative limit is a good idea when possi- ble, especially if you may have to exert yourself during decompression (due to current, etc.) c. Note to imperial system divers: The PO2 of pure oxygen at 20 feet of sea- water is 1.61 – the .01 difference is ignored because it’s physiologically insignificant, and the depth difference is less than 3 inches. Although you won’t use pure oxygen at the Tec 40 level, higher level tec divers routinely use oxygen at 20 feet. 3. As with the EADs, you find your PO2s and maximum depths by: a. Using formulas. PADI ® 4-32 padi.com
  33. 33. Instructor Guide Section four: Tec40 b. Looking them up on tables such as the DSAT Equivalent Air Depth Table or the Maximum Depths Table found in the Appendix of the Tec Deep Diver Manual (formulas are in the Appendix, too.) c. Using desk top decompression software like you’ll be applying in this course. [Go through one or two problems to find PO2s at different depths and maxi- mum working phase and decompression phase depths, for different blends for- mulas. Then use the tables, which is the simplest and most practical method.]C. Gas consumption 1. In this course, you’ll learn to plan gas use based on how fast you consume it. a. Your Surface Air Consumption (SAC) rate is the rate you use gas (in litres or cubic feet per minute) if swimming at a moderate speed in all your equipment at the surface. b. SAC changes with equipment and anything else affecting drag. c. SAC changes as you gain skill and fitness, and with physical variables such as temperature. d. SAC can be expressed in bar/psi per minute, or gas volume per minute. e. You’ll also hear references to Respiratory Minute Volume (RMV), and it is often the term used in decompression software. The medical community defines RMV as: PADI ® padi.com 4-33
  34. 34. Section four: Tec40 Instructor Guide RMV = Vt -Vd x respiratory rate where Vt = tidal volume, Vd = respiratory dead air space and respi- ratory rate = breaths per minute. • Tec divers sometimes use RMV to mean SAC rate based on volume – this is not technically accurate, but close enough. • You’ll hear SAC rate and RMV used interchangeably; this is fine, but do not confuse SAC rate based on bar/psi with SAC rate based on volume. They’re not the same thing. 2. Finding your SAC rate – use this formula: [Make up other examples and work through them until you’re confident students understand and can apply the formula.] Emphasis Note to Students Sometimes SAC is determined as bar or psi in- stead of volume per minute. This isn’t useful in technical diving because bar/ psi per minute depends upon the specific cylinder type. 3. You may want to determine your SAC rate at rest for decompression/safety stop planning, so you will know both your working SAC rate and your decompres- sion SAC rate. 4. You need to adjust your SAC rate up or down based on your expected exer- tion during the dive. When in doubt, estimate upward. 5. As you gain experience, your SAC rate tends to get smaller; check periodi- cally and when making substantial equipment changes. 6. Estimating your gas requirements for a given depth: a. You’ll use your SAC rate to estimate gas supply requirements. At the Tec 40 level you will do this by entering your SAC rate into decompression software, which calculates your gas supplies for you. But, you should know how it is calculated so you can recog- nize should your software be off (usually due to entry errors). b. To determine your estimated gas supply requirement for a given depth:PADI ® 4-34 padi.com
  35. 35. Instructor Guide Section four: Tec40 [Go through several examples until you’re confident students understand and can apply the concept.] 7. Reserve a. Since gas supplies are estimates, to allow for the unforeseen, you always plan a reserve. The most common reserve for technical div- ing is 33 percent (“thirds” or “rule of thirds”). This means 33 percent of your supply is purely for contingency use. The higher the percent, the more reserve. b. To determine your gas requirements with reserve, use this formula: PADI ®padi.com 4-35
  36. 36. Section four: Tec40 Instructor Guide or gas required ÷ .66 = total gasD. Actual gas supply 1. Once you know how much gas you need, you also need to know how much gas you have when you start the dive. Note that while software will calcu- late how much gas you need, there are not many programs that calculate how much you have – you have to do it. To do so, you calculate the vol- ume based on the pressure. How you do this varies slightly with the metric and imperial systems. 2. Metric system: Cylinders are designated by their nonpressurized internal volume in litres. Simply multiply the designated volume by the pressure in bar; for doubles, multiply that by two: Example: An 11 litre cylinder has 185 bar in it. What is the available gas supply? Answer: 2035 litres. (11 x 185 = 2035 litres). 3. Imperial system: Cylinders are designated by their capacity in cubic feet at their working pressure. a. One way to find gas supply is to divide the actual pressure by the working pressure and multiply that by the designated capacity. (A/W x C = cubic feet) PADI ® 4-36 padi.com
  37. 37. Instructor Guide Section four: Tec40 Example: An 80 cubic foot cylinder, working pressure 3000 psi, has 2500 psi in it. What is the available gas supply? Answer: 66.6 cubic feet. (2500 ÷ 3000 = .83, .83 x 80 = 66.6 cubic feet) b. Another, more popular way is the baseline method. A base- line is how many cubic feet cylinders hold per psi, which you multiply by the actual psi. • To get the baseline, divide the designated capacity by the working pressure. Then multiply the result by the actual pressure. Example: An 80 cubic foot cylinder, working pressure 3000 psi, has 2500 psi in it. What is the available gas supply? Answer: 66.8 cubic feet. (To get the baseline: 80 ÷ 3000 = .0267; .0267 x 2500 = 66.8) Note the slight difference with the previous example due to rounding. Example: A set of double 80 cubic foot cylinders, working pressure 3000 psi, have 1850 psi in them. What is the avail- able gas supply? Answer: 132.5 cubic feet. (To get the baseline: 80 x 2 ÷ 3000 = .053; .053 x 1850 = 98.05) • The advantage of the baseline method is that you can determine the baselines for the cylinders you use frequently and record them in your log book. Then you only have to multiply the cylinder base- line by your SPG reading to determine the gas vol- ume you have. 4. Keep in mind that the popular designation may be rounded. (Example, some types of the imperial system aluminum “80” actu- ally hold 78.2 cubic feet at the working pressure). This normally isn’t a huge issue, but may be if your required gas supply and sup- ply available are very close. 5. If you find your gas supply available isn’t adequate for the dive you’ve planned, you need to recalculate a shorter dive, or get more gas to cover the dive. PADI ®padi.com 4-37
  38. 38. Section four: Tec40 Instructor GuideE. Oxygen toxicity 1. You recall that exposure to high oxygen partial pressures can cause Central Nervous System (CNS) oxygen toxicity and pulmonary oxygen toxicity. 2. Unacceptable risk of CNS toxicity results from an exposure to a PO2 above 1.4 ata/bar during the working phase of the dive and 1.6 ata/bar during the resting/decompression phase. a. The primary symptom/sign is a convulsion, which can cause drown- ing underwater. b. Warning signs/symptoms usually do not precede a convulsion, but if they do, include visual disturbances, ear ringing or sounds, nausea, twitching in facial muscles, irritability and restlessness, and dizzi- ness. (Remember VENTID - vision, ears, nausea, twitching, irritabil- ity, dizziness) c. You must accept the risk that, under rare circumstances, CNS oxygen toxicity can occur at lower PO2s than 1.4/1.6. d. Although your risk diminishes when you drop your PO2, you can still have a convulsion after ascending or switching to a gas with less oxygen. 3. Pulmonary toxicity results from long term exposure to PO2s above .5 ata. It is not immediately life threatening. a. Signs/symptoms include lung irritation, a burning sensation in the chest, coughing and reduced vital capacity. b. Although highly unlikely in recreational enriched air diving, pulmo- nary toxicity is possible in technical diving, especially after using oxygen for decompression.F. Managing oxygen exposure 1. You manage oxygen exposure to avoid both forms of oxygen toxicity. 2. The DSAT Oxygen Exposure Table and other variations on the “CNS clock” are one way to manage pulmonary toxicity. a. It is based on allocating exposure as a percentage of the maximum allowed by NOAA oxygen limits. (See the Oxygen Limits Table in the Appendix of the Tec Deep Diver Manual.) b. It is misnamed the “CNS clock” because the methodology was thought (somewhat inaccurately) to manage CNS exposure. Actually, it primarily manages pulmonary oxygen toxicity. c. You’ll learn more about using the CNS “clock” in the Tec 45 and Tec PADI ® 4-38 padi.com
  39. 39. Instructor Guide Section four: Tec40 50 courses. Provided you keep your PO2 above 1.4 bot- tom/1.6 deco, oxygen toxicity is highly unlikely within Tec 40 dive limits. 3. Oxygen Tolerance Units (OTUs) also manage pulmonary toxicity. a. OTUs are dose units of oxygen assigned based on daily exposures and cumulative exposures. b. You’ll learn more about OTUs and using them in the Tec 45 and Tec 50 courses. 4. Whether using air, enriched air or oxygen, the primary methods for tracking pulmonary toxicity-related oxygen exposure are: a. OTUs/CNS clock by using tables and formulas (more about these in the Tec 45 and Tec 50 courses). b. OTUs/CNS clock automatically tracked by a dive computer (far more practical – one way you will track oxygen expo- sure as a Tec 40 diver). c. OTUs/CNS clock automatically calculated by decompres- sion software (more practical, and useful for planning dives with dive computers – you will also do this as a Tec 40 diver). 5. Whether using air, enriched air or oxygen, the primary method for managing CNS toxicity related oxygen exposure is to keep your PO2 at or less than 1.4 ata/bar (working or bottom phase) or 1.6 ata/bar (decompression/safety stop phase). a. CNS toxicity is very unpredictable when a diver exceeds 1.4 - 1.6 ata/bar PO2. Because there are too many strong phys- iological variables, there is not a useful relationship between exposure and partial pressure. The same diver can have no problems at high PO2 for hours one dive, and con- vulse in minutes at a lower PO2 in another. b. Stay well within limits – there’s generally no real dive time benefit or decompression advantage of pushing them. PADI ®padi.com 4-39
  40. 40. Section four: Tec40 Instructor GuideG. The Equivalent Air Depth and Oxygen Management Tables in the Appendix of the Tec Deep Diver Manual list EADs, PO2s, “CNS clock” percent per minute and OTU per minute for 21 percent oxygen through pure oxygen. You will not need to use these as a Tec 40 diver, but you should be beginning to understand why these concepts are increasingly important as you dive deeper and make longer decom- pressions using gases with up to 100 percent oxygen.other Delivery Content, Tec 40-3 Study assignment: Tec 40 Handout 3Learning ObjectivesBy the end of this section, you should be able to answer these questions:1. What is the maximum oxygen blend you would use as the bottom gas for a dive to 40metres/130 feet?2. What is the maximum percentage of oxygen you will use as a Tec 40 diver?H. As a Tec 40 diver, your maximum allowable depth is 40 metres/130 feet. 1. Using the maximum depth tables on pages 266 and 267, you find that EANx28 is the highest oxygen content gas blend you can use at 40 metres/130 feet (PO2 = 1.4 ata/bar). 2. You may use blends with more oxygen, but at increasingly shallower maxi- mum depths. 3. With blends that have 36 percent or more oxygen, your maximum depth is so shallow and your no decompression time is so long that you probably won’t have to make decompression dives at all.I. The maximum oxygen percentage you’re qualified to use as a Tec 40 diver is 50 percent (EANx50). You will normally use this as a decompression gas (you can use it as a bottom gas, but the maximum depth is 18 metres/59 feet – you will probably not need to decompress on such a dive). 1. The maximum depth for using EANx50 as a decompression gas (PO2 = 1.6) is 21m/70 ft (See the Equivalent Air Depth and Oxygen Management Tables for 50% on pgs 274 & 288). PADI ® 4-40 padi.com
  41. 41. Instructor Guide Section four: Tec40 2. You may be carrying EANx50 (or other deco gas) to a depth deeper than you can safely breathe it. It is critical to follow all gas handling proce- dures to avoid accidentally switching to it at too deep a depth. You will learn and practice these procedures beginning with Tec 40 Training Dive One.Exercise, Other Delivery Content, Tec 40-31. The maximum oxygen enriched air you would use as bottom gas for a dive to 40metres/130 feet iso a. EANx28.o b. EANx32.o c. EANx36.o d. EANx50.2. The maximum oxygen content enriched air that you’re qualified to use as a Tec 40diver iso a. EANx28.o b. EANx32.o c. EANx36.o d. EANx50.How did you do?1. a. 2. d. PADI ®padi.com 4-41