TDI changing deco procedures course
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Maybe post this in the SDI/TDI forum, rather than the SSI?
EDIT: Mod moved this thread, thanks!
EDIT: Mod moved this thread, thanks!
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I can give you an opinion - I doubt that we would see a change on the Deco Procedures course in terms of using Trimix.
To my mind, the combination of Advanced Nitrox and Decompression Procedures is providing the basic skill sets required for ongoing technical diving. Just because there is a 45m limit on DP doesn't mean that you have to train to that limit.
To give you an idea, the way we run our AN&DP courses, we typically do the first 3 dives in 10m of water, just drilling basic skills. The next 3 dives will be to a max depth of around 30m, where the content of each dive is application of skills in certain contexts, e.g. ascents. Finally, we would do two "experience" dives, typically one that was 40-42m max with a bottom time of 20-25 minutes and then the final dive being shallower (32-25m) for longer (45-50 minutes).
Yes, it would be nice to limit END to 30m or so for the one dive on the course. Realistically, though, students have a lot to come to grips with and need a period of consolidation in terms of getting their skills perfected before extending their personal depth limit.
There is a natural tendency for divers to dive straight to the limits of the gas straight after a course - introducing normoxic trimix in entry level technical courses will tempt new technical divers to straight away think 55m+ dives. AN&DP is limited to introducing basic skills and a single deco gas.... 55m+ introduces the need for a lot more dive planning and thought, and realistically a second deco gas. That's a whole bunch of skills that aren't covered in AN&DP, but are covered in Extended Range or Normoxic Trimix.
There has been a lot of discussion in the past on the role of the Extended Range course - try searching for that, and you'll see plenty of discussions related to TDI, deep air and trimix. You should be able to draw your own conclusions from that.
To my mind, the combination of Advanced Nitrox and Decompression Procedures is providing the basic skill sets required for ongoing technical diving. Just because there is a 45m limit on DP doesn't mean that you have to train to that limit.
To give you an idea, the way we run our AN&DP courses, we typically do the first 3 dives in 10m of water, just drilling basic skills. The next 3 dives will be to a max depth of around 30m, where the content of each dive is application of skills in certain contexts, e.g. ascents. Finally, we would do two "experience" dives, typically one that was 40-42m max with a bottom time of 20-25 minutes and then the final dive being shallower (32-25m) for longer (45-50 minutes).
Yes, it would be nice to limit END to 30m or so for the one dive on the course. Realistically, though, students have a lot to come to grips with and need a period of consolidation in terms of getting their skills perfected before extending their personal depth limit.
There is a natural tendency for divers to dive straight to the limits of the gas straight after a course - introducing normoxic trimix in entry level technical courses will tempt new technical divers to straight away think 55m+ dives. AN&DP is limited to introducing basic skills and a single deco gas.... 55m+ introduces the need for a lot more dive planning and thought, and realistically a second deco gas. That's a whole bunch of skills that aren't covered in AN&DP, but are covered in Extended Range or Normoxic Trimix.
There has been a lot of discussion in the past on the role of the Extended Range course - try searching for that, and you'll see plenty of discussions related to TDI, deep air and trimix. You should be able to draw your own conclusions from that.
TDI used to certify divers to 180 ft with the combination of Advanced Nitrox and deco procedures, but backed it off to 150'. Prior to the change in max depth, the major difference between that combination and Extended Range were things like procedures with travel gasses, etc.
Extended Range still certs the diver to 180', but TDI also promotes a basic/normoxic trimix option. The major difference is that the last two dives in the course are done with trimix and the diver is then certed to 200' on trimix rather than to 180' on air. Advanced nitrox then certs divers in the sue of hypoxic mixes to a max depth of 300'.
Personally, I don't have any serious problem with dives to 150' on a suitable nitrox mix as opposed to trimix, as long as the conditions allow it - and with recognition that individual diver's mileage may vary.
I also think most divers who get the advanced nitrox and deco procedures cert would only rarely push it to 150. Plus a dive to 150' is not a requirement to obtain the cert, so students and/or instructors can scale the max depth back if desired.
Extended Range still certs the diver to 180', but TDI also promotes a basic/normoxic trimix option. The major difference is that the last two dives in the course are done with trimix and the diver is then certed to 200' on trimix rather than to 180' on air. Advanced nitrox then certs divers in the sue of hypoxic mixes to a max depth of 300'.
Personally, I don't have any serious problem with dives to 150' on a suitable nitrox mix as opposed to trimix, as long as the conditions allow it - and with recognition that individual diver's mileage may vary.
I also think most divers who get the advanced nitrox and deco procedures cert would only rarely push it to 150. Plus a dive to 150' is not a requirement to obtain the cert, so students and/or instructors can scale the max depth back if desired.
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Deco procedures (which is usually combined with advanced nitrox) has been a mainstay of our curriculum since being introduced in 1994/95. So too has trimix. The decompression class and ALL the skills required for the course, can be taught successfully in 30 to 35 metres.
We feel there is value in the curriculum as it stands and there is no need to add or subtract anything from existing courses. This has nothing at all with promoting deep air. We do not. In fact several instructors, myself included, keep nitrogen loading to 3.1 3.2 bar during training in decompression. The 150 feet is a maximum depth and we have never mandated that depth to any of our instructors when we train them. The skills document (and our president Brian Carney) makes it clear that diving in ANYTHING but warm, clear, calm water with a PN2 higher than about a hundred foot equivalent is unnecessary.
Students who wish to dive deep are strongly encouraged to undertake a trimix class.
As Andy recognizes, there is the temptation for abuse by so-called recreational trimix divers. I have seen divers with this level of certification attempting to conduct full decompression dives with decompression gases and hypoxic mixes.
We DO have instructors, several on the west coast and some in the Great Lakes, who offer a distinct specialty which includes light helium in their decompression classes. Frankly, it seems unnecessary in all but exceptional cases (see above).
If you have been coerced into diving deeper than you are comfortable with by a TDI instructor, please send me a private email with full details: dates, location, course name, your name, your instructor's name. Thank you.
A sidebar: If you wish to have input from HQ staff, please post in the the correct forum. We do not monitor the other agency forums as regularly as our own.
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Atomic_Diver
Scubaboard Enthusiast
why not combine/come up with a course combo like Deco procedures that has Adv nitrox, and includes a course like IANTD's Advanced Recreational Trimix (which certifys divers to 165' using helium mixtures not to execeed a END of 80')???
One reason is helium molecules are smaller than nitrogen molecules so you in gas and off gas faster. This makes ascent rates, buoyancy and time at stop even more critical and adds additional task loading/stress to students who have enough on their plate to begin with.
Crawl walk run.
walke121
Contributor
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