The usefulness of deco training without trimix

[stuartv]

I don't think it's a great example

ps. My only point about that was to illustrate the extreme to which you can take AN/DP certification without exceeding your training. Thus to show how useful it can be without having to move up to Trimix. I'm not recommending to do dives like that. I'm just saying you CAN (without exceeding your training or certification).

 

[beester]

ps. My only point about that was to illustrate the extreme to which you can take AN/DP certification without exceeding your training. Thus to show how useful it can be without having to move up to Trimix. I'm not recommending to do dives like that. I'm just saying you CAN (without exceeding your training or certification).

Well my point is that there is much to learn and it's better to take baby steps instead of having a 6 dive course that tries to teach everything. Obviously you can take those steps on your own... but that is already covered in another topic that you posted.

Just going on certifiication limits you wouldn't be able to do that dive after a GUE T1 course . T1 is the equivalent of AN/DP/Normoxic. I'm not sure going to the "extremes" of a course that is already packed full with stuff (you mentioned heliox and 2 stages) is a sound strategy? I've been very close to an IANTD normoxic plus course recently. The students came from an essentials plus AN background and decided to go for the 2 stage 200ft course instead of the regular normoxic class, probably to safe some money and why not right? Without going into details it didn't go very well.

There are reasons why most courses are structured like this (more or less)
- AN/DP (40-45m and 1 stage, limited deco)
- Normoxic or extended range (air) (50-65m, no limit on deco but most in the 30 min to 1 hour deco range, 1 or 2 stages depending)
- full trimix (hypoxic gasses, 70m+, multiple stages, 1 hour plus deco)

I think you should be looking at what you were thought in the course... and gradually move from there... were you doing 130ft 45' dives on the course... I don't think so... If you are moving so far away from the initial course and you are ready forr that kind of diving... why not take another course or look for a mentor... ?

But hey it's of course a risk vs reward vs cost discussion. And I definitely am not trying to "attack" you... Free world and whatever you decide to do you decide to do. But I'm not sure that stating what for TDI (not sure other agencies) are the extreme limits of diving with an AN/DP certification after the course is really relevant.

 

[stuartv]

Well my point is that there is much to learn and it's better to take baby steps instead of having a 6 dive course that tries to teach everything. Obviously you can take those steps on your own... but that is already covered in another topic that you posted.

Just going on certifiication limits you wouldn't be able to do that dive after a GUE T1 course . T1 is the equivalent of AN/DP/Normoxic. I'm not sure going to the "extremes" of a course that is already packed full with stuff (you mentioned heliox and 2 stages) is a sound strategy? I've been very close to an IANTD normoxic plus course recently. The students came from an essentials plus AN background and decided to go for the 2 stage 200ft course instead of the regular normoxic class, probably to safe some money and why not right? Without going into details it didn't go very well.

There are reasons why most courses are structured like this (more or less)
- AN/DP (40-45m and 1 stage, limited deco)
- Normoxic or extended range (air) (50-65m, no limit on deco but most in the 30 min to 1 hour deco range, 1 or 2 stages depending)
- full trimix (hypoxic gasses, 70m+, multiple stages, 1 hour plus deco)

I think you should be looking at what you were thought in the course... and gradually move from there... were you doing 130ft 45' dives on the course... I don't think so... If you are moving so far away from the initial course and you are ready forr that kind of diving... why not take another course or look for a mentor... ?

But hey it's of course a risk vs reward vs cost discussion. And I definitely am not trying to "attack" you... Free world and whatever you decide to do you decide to do. But I'm not sure that stating what for TDI (not sure other agencies) are the extreme limits of diving with an AN/DP certification after the course is really relevant.

Uhhh... the dive I gave as an example wasn't my first deco dive after certification. I started AN/DP 2 years ago. I finished it well over a year ago. I have done a number of smaller deco dives in the meantime. I would say I have "looked at what I was taught and gradually moved from there." I was taught with 1 AL40 for deco. Over a year later, I have now moved up to 1 AL80 for deco gas - and planned a longer dive (in recreational depth limits, no less) as a result. That doesn't sound like a big leap to take, after over a year of smaller dives. How many dives and how long should I wait before expanding my personal limits some while still staying within my certification limits?

I agree that the extreme example I gave is not one anyone should do right after they finish AN/DP. Oh, and I said that AN/DP/Helitrox standards require 1 deco gas. The instructor has the flexibility to teach 2 deco gases if they want. My instructor does not teach that in his AN/DP/Helitrox course. I did also say that I have since (as in, a year later) been taught how to use 2 deco gases and am starting to practice with that. Only practice, at this point.

Why wouldn't you be able to do that dive after a GUE T1 course? It was 130', 47 minutes bottom time, with one deco gas. I'm very surprised to hear that GUE T1 wouldn't give you the tools to do that.

Again you have said that "most" courses have limited deco as their first step. What are the ones that do have that limit? TDI AN/DP does not. PADI's equivalent to AN/DP (Tec 45) does not. Tec 40 does, if you want to count that, but it has a time limit on deco, only allows up to 50% for deco gas, and does not even require doubles (you can do it with a single backmounted cylinder rig), so I would count that one as advanced recreational - not a first tech diving course.

Again, I make the point that AN/DP gives you the tools to do plenty of good diving (with one extreme example given). That doesn't mean anyone should do the class and immediately go out and push their limits. Hopefully, that is something that would get drilled into them by their instructor. "Here are your tools. You can do a LOT with them. Start out by doing a little and gradually work your way up from there. The same tools will carry you a long way without further investment (in tools)."

 

[Doby45]

Another good case for AN/DP and not straight Trimix is cave diving. You can be in a system that the average depth will put you into deco but not so deep that you need trimix. You can go in Little River to the Florida room with nitrox and hit a bit of deco on the way out. So AN/DP is not necessary ONLY for depths that trimix would be beneficial but any dive that could put you into deco..

 

[beester]

Heya Stuart... I totally dig what you are saying. Sorry for "busting your balls" a bit... This seems much more reasonable, with a much more gradual move into more extensive decompression.

There is a reason why you (and most) start out with a 40cuft stage tank in their AN/DP/etc course. And a little secret, it's not (only) because it's an easy to handle little light stage, and a very nice and comfortable first step into stage diving. No the real reason is that it has a very limited volume allowing the students to taste decompression after the course but not get in head over heels because the volume of deco gas prohibits very extensive deco.

Yes GUE T1 has following certification limits:
Trimix 21/35 and 18/45
50% or O² as deco gas (1 deco stage, no bottom stage)
Max depth 51m
Max deco 30 minutes

Then you have T60 which is an intermediate which extends above to 2 stages (1 bottom and 1 deco or 2 deco) and extends depth to 60m (200ft) and deco to 45 min I think

And finally you have T2 and T2plus (which is a certification but covered in T2, you don't do another course after that...) which is full trimix multiple stages hypoxic mixes.

Reason GUE does it like that at normoxic T1 level is the 1 stage. In our lost deco gas scenario's you potentially could start running into difficulties doing 45min or more on 1 stage. Since you are only taught how to handle 1 stage they limit the max deco just to prohibit your example ... What you do on your own is of course what you do on your own.

To the OP: (because I went so off topic)... I believe AN/DP is a very good entry level technical course that lets you taste from decompression diving. If the majority of your diving range (and the charters boats allow the extended time) is in this depth range I would go for it. You'll learn a lot and be able to gradually extend your range.

If after a while you see that you are really pushing the deco time to over 40 minutes I would start looking into multi stage diving and or trimix.


Cheers

B

 

[stuartv]

Heya Stuart... I totally dig what you are saying. Sorry for "busting your balls" a bit... This seems much more reasonable, with a much more gradual move into more extensive decompression.

No worries. I've been on SB for almost 3 years. I am very used to people making assumptions and in the negative direction. Not really trying to bust your balls, either. It's just a fact of life around here. That's why I don't get particularly riled up about it.

There is a reason why you (and most) start out with a 40cuft stage tank in their AN/DP/etc course. And a little secret, it's not (only) because it's an easy to handle little light stage, and a very nice and comfortable first step into stage diving. No the real reason is that it has a very limited volume allowing the students to taste decompression after the course but not get in head over heels because the volume of deco gas prohibits very extensive deco.

Right. That was no secret, to me.

Yes GUE T1 has following certification limits:
Trimix 21/35 and 18/45
50% or O² as deco gas (1 deco stage, no bottom stage)
Max depth 51m
Max deco 30 minutes

Then you have T60 which is an intermediate which extends above to 2 stages (1 bottom and 1 deco or 2 deco) and extends depth to 60m (200ft) and deco to 45 min I think

And finally you have T2 and T2plus (which is a certification but covered in T2, you don't do another course after that...) which is full trimix multiple stages hypoxic mixes.

Thanks for the explanation. Very interesting. I had been assuming (there we go again!) that GUE Tech 1 was basically normoxic and Tech 2 was hypoxic. Since GUE teaches trimix almost right off the bat (i.e. Rec 3?), and has such stringent requirements to get in (i.e. Fundies Tech pass) I didn't find it hard to believe that Tech 1 would be full normoxic trimix (i.e. unlimited deco, to 60m). I didn't know about the "extras" like T60 and T2Plus.

 

[kensuf]

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.

You got screwed on your AN/DP course then.

 

[kensuf]

I don't have the course materials and standards from that era, but I think that AN as a stand alone course did not include ANY decompression in the course.

It is hard to say what your experience was, though. I took AN and DP at about that time myself, but I never had any idea what the course standards were. The course materials don't tell you what the standards are, and our instructor was certainly not going to tell us. He did tell us that although we would have to complete the written exams on the course materials, the course itself was going to ignore the TDI curriculum and standards completely. We were going to follow the standards for GUE Tech I instead. It was not until I became a TDI instructor myself and saw the (updated) course standards that I saw how different the course as written was from the course I took. (I also know he was not following the GUE standards, either.) I was peeved enough at not getting a certification card when I thought I deserved one that I contacted TDI, told them what we were doing, and asked about the standards. They responded by telling me that TDI instructors are allowed to go as far outside of standards as they wished, as long as the standards are met.

So, your instructor in 2006 was then (and would be today) completely free to add whatever he or she wanted to the class.

I dug through my filing cabinet and pulled out a copy of the TDI S&P from 1997. TDI Advanced Nitrox was not a decompression course back then.

However, IANTD Advanced Nitrox does (and did) allow for 15 minutes of decompression.

IMHO, Advanced Nitrox has limited usefulness without decompression procedures.

 

[RyanT]

You got screwed on your AN/DP course then.

Ken, I appreciate your perspective from your extensive experience. I don't think so though. In my AN/DP course, I learned to plan a deco dive, manage a single stage, deal with OOG scenario, both on back gas and in deco, conduct valve drills, ascend with an unconscious diver, manage a lost mask scenario on ascent, both for buddy and myself and various other tasks. A few of these tasks were compounded.

In my trimix course, I learned additional planning for deeper dives with helium and longer decos and managing two stages. Then my instructor stepped us up to dealing with multiple failures in the dive team. In one case within our four man dive team, we had to simultaneously manage an OOG diver, a lost mask diver, an unconscious diver, a failed stage, and do all of this ascending in one the most ripping currents I've experienced in my entire dive career. I wasn't prepared for this level of task loading in my AN/DP course

Maybe I don't have the perspective, but I'm quite happy with my training.

 

[Centrals]

I do enjoy IANTD Deep Air and Adv Nitrox course back in 1998.
Twin set + one 50% deco mix. Deco was actually very short.
A great introduction to Technical diving. If I remember correctly both courses were NOT regarded as tec course.