The usefulness of deco training without trimix

[kensuf]

Comparing AN/DP to GUE Tech 1 is tough. A better comparison would be AN/Helitrox + Normoxic Trimix to Tech 1, but even then it's going to really depend on the instructor.

 

[AJ]

Anyway, the point was to illustrate that AN/DP has good value in its own right. It doesn't have to be just a stepping stone to Trimix. Just because it will allow you to do some pretty serious, long deco dives doesn't mean you have to do dives that are that "big". It just means you can.

The problem as I see it would be finding buddy's trained to do these kind of dives. My buddy's are Trimix trained or OW/AOW. If you know some divers who are trained alike, it can be very usefull. The same goes for Trimix.

 

[beester]

TDI AN/DP certification is for unlimited deco.

The example I gave was a dive with a plan that included coverage for the possibility of lost deco gas. Specifically, that is why my buddy and I both had an AL80 of deco gas.

Anyway, the point was to illustrate that AN/DP has good value in its own right. It doesn't have to be just a stepping stone to Trimix. Just because it will allow you to do some pretty serious, long deco dives doesn't mean you have to do dives that are that "big". It just means you can.

Maybe TDI not, but most AN certs have a definite deco limit. The dive you describe is although not from depth point of view but certainly deco point of view a normoxic plus dive. Not the scope of the OPs request.

PS: didn't know that TDI AN/DP had only a limit on depth, but not on deco time. Most other certification agencies do limit both. On one hand we are all adults, there is no scuba police and free world kinda thing... on the other hand, not sure if 1 course can teach you enough skills (certainly if it's the first technical course) and procedures to do significant deco dives (45' deco is in my book significant). Is there a stage limit? (like in only 1 stage allowed)?

 

[2airishuman]

Thanks for the many insightful replies.

Maybe TDI not, but most AN certs have a definite deco limit. The dive you describe is although not from depth point of view but certainly deco point of view a normoxic plus dive. Not the scope of the OPs request.

PS: didn't know that TDI AN/DP had only a limit on depth, but not on deco time. Most other certification agencies do limit both. On one hand we are all adults, there is no scuba police and free world kinda thing... on the other hand, not sure if 1 course can teach you enough skills (certainly if it's the first technical course) and procedures to do significant deco dives (45' deco is in my book significant). Is there a stage limit? (like in only 1 stage allowed)?

The TDI AN/DP course has been around for a while and still takes the approach that it provides foundation knowledge and skills that serve as a starting point. After completing the class, the diver is expected to dive within their personal limits, which may expand with time, experience, and mentoring. Hence there is no limit on the number of stages or the duration of deco.

This is an approach that works better in my situation than either the GUE approach (lengthy, comprehensive classes that produce fully skilled divers) or the PADI approach (a structured series of classes that formally set limits which gradually expand as more classes are taken).

 

[Stoo]

Understanding deco is critical for any form of advanced diving. As mentioned above, a certain percentage of the dive community "freaks" at the mere thought of slipping past those pesky NDLs.

With regard to Trimix, IMHO, "deco" and "trimix" are two completely separate things. Obviously there is lots of overlap, but a diver can easily get into deco without diving mix. The vast majority of the diving I do in the Great Lakes is like this... 100' - 160', bottom gas is air and using a high percentage O2 for deco. It isn't just about depth of course, it's about time too.

With the water in Tobermory being toasty now (above the thermocline) having to do a 15 or 20 minute deco stop is quite pleasant.

Another scenario is the "advanced vacation diver" where multiple dives in a day, over several days lead to significant amounts of accumulated nitrogen. Having the knowledge and skills to comfortably manage "actual" decompression obligations is reassuring. (I am not advocating repeated deco dives on vacation!)

Even if you never plan on getting into mix or planned deco dives, there are many advantages to understanding how to deal with a surplus of inert gas in yer corpuscles~

 

[Divin'Papaw]

Yes, absolutely! I did AN/DP 9 years before eventually adding Trimix training. They are very useful skills in and of themselves and I utilized them regularly (still do) both on advanced recreational dives and on decompression dives. Also, I did this primarily diving in the Great Lakes and deep inland lakes/quarries in the Midwest.

Even though I've completed trimix training now, I only plan to utilize it for deep wreck dives on occasion. It is expensive on open circuit! However, the base AN/DP skills I utilize far more regularly.

 

[beester]

Thanks for the many insightful replies.



The TDI AN/DP course has been around for a while and still takes the approach that it provides foundation knowledge and skills that serve as a starting point. After completing the class, the diver is expected to dive within their personal limits, which may expand with time, experience, and mentoring. Hence there is no limit on the number of stages or the duration of deco.

This is an approach that works better in my situation than either the GUE approach (lengthy, comprehensive classes that produce fully skilled divers) or the PADI approach (a structured series of classes that formally set limits which gradually expand as more classes are taken).

Although I do honestly feel that GUE courses are very comprehensive I think you are mistaken thinking divers that come out of such a course are fully skilled .... nope just like any other course from any other organisation the cert is just a driving license, and after the course you need to gain experience... in baby steps.

On the Trimix thing... Well to be honest GUE T1 (normoxic trimix) encompasses obviously the full AN/DP and extends this to trimix. But to be honest trimix is just a gas... the bread and butter of the course is in how to plan and handle a deco dive (how you act on a boat, gas and deco plan, team awareness, ascend strategies, switching, etc)... 98% of that has nothing to do with the bottom gas you breath (although GUE limits to an END OF 30m).

We are currently doing project work on a protected shallow North Sea wreck (depth range 90-110ft) and this is obviously done with 32% (or tx 30/30 if it's heavy work)... so we aren't using trimix normally but obviously we are still doing deco dives

 

[stuartv]

Maybe TDI not, but most AN certs have a definite deco limit. The dive you describe is although not from depth point of view but certainly deco point of view a normoxic plus dive. Not the scope of the OPs request.

PADI Tec 45 is the direct equivalent of TDI AN/DP. It also has no limit on deco time, AFAIK. When you say "most", what ones are you talking about? PADI Tec 40 does have a time limit, I think. I think it also limits you to a max of 50% on your deco gas. I would not count that as anything like equivalent to Adv Nitrox.

And what makes the dive I described a "normoxic plus dive"? My max depth was pretty much exactly at the limits of normal sport diving. I couldn't see any need at all for trimix (though I understand some folks would also use trimix deeper than 100').

TDI AN/DP standards require training for use of 1 deco gas, but they do not limit the training. The instructor can train for multiple deco gases if he or she wants to. My instructor only trains for 1 deco gas at the AN/DP/Helitrox level. He trains for 2 when you move up to TDI Trimix. Thus, my training is only for 1 deco cylinder and that is why I only used 1 deco gas on that particular dive.

However, my instructor has now taught me the procedure for using 2 deco gases and I'm starting to practice with 2 cylinders in the water. I will not be in violation of my TDI certification limits when I am ready and start to use 2 deco gases, even if I have not completed TDI Trimix at that point.

With regard to Trimix, IMHO, "deco" and "trimix" are two completely separate things.

Excellent point! Use of helium is for managing narcosis. Thus, use of trimix is all about the depth you are diving. It's really nothing to do with how long the dive is. It just kind of goes hand in hand with deco diving because dives deep enough to warrant use of helium are going to be pretty dang short if you don't allow yourself to go into deco.

But, there is nothing about deco dives, per se, that requires helium. Deco is about how long you stay down. Helium is for going deeper. Mix and match as required. If you're only going to do deco dives within recreational depth limits, there really is no NEED for trimix.

 

[Stoo]

. Deco is about how long you stay down. Helium is for going deeper. Mix and match as required. If you're only going to do deco dives within recreational depth limits, there really is no NEED for trimix.

Precisely. Most of the diving I do is what I call "tecreational". I dive air on many dives where "some" would say He is recommended, but honestly, I don't seem to get narc'd too readily and because I do these dives all the time, the cost would be brutal. I did four dives last week in the 130' to 155' range and wracked up a total of 70 minutes of deco... air dives, O2 for 10' and 20' stops.

I allow deep stops on my Petral, do two of those dives included 50' "stops" although that stop was cleared my the time I got there...

 

[RyanT]

Excellent point! Use of helium is for managing narcosis. Thus, use of trimix is all about the depth you are diving. It's really nothing to do with how long the dive is. It just kind of goes hand in hand with deco diving because dives deep enough to warrant use of helium are going to be pretty dang short if you don't allow yourself to go into deco.

But, there is nothing about deco dives, per se, that requires helium. Deco is about how long you stay down. Helium is for going deeper. Mix and match as required. If you're only going to do deco dives within recreational depth limits, there really is no NEED for trimix

As I discovered, there is a lot more to trimix than just adding helium to manage narcosis. In fact, in my experience, helium was really the least important part of the course. The real value I got from my trimix course was additional planning, managing two stages AND doing that with additional task loading and handling multiple simultaneous failures with your team. What my instructor required of us was quite a big step up from AN/DP.