The usefulness of deco training without trimix

[gobuyastick]

The biggest "limit" to tech1 is the use of a single deco gas.

Signing up for more than ~30mins of deco or depths greater than 170 or is not wise with a single deco gas.

ik im just fundies certified but how would you plan a strict tech1/cave2 dive, as in bringing only 50% and not allowing anymore than 30min of unadjusted deco? also as the diver gets more experience and extends their bottom time in the deeper caves couldnt they bring stages along a bottle of O2 (both of whicthey got from their cave 2 card) with their 50% bottle instead of waiting to get tech 2 certified? i get that theres no scuba police to stop someone, but if the diver slowly adds on the complexities i dont see the big deal imo.

 

[macado]

A lot of good answers already so I don't know how much value my comments will add. I'll just be blunt and saying having AN/DP (or equivilant) training AND experience before trimix is absolutely critical in skills development. Consider it a valuable stepping stone. Of course I'm also one for saying proper mentoring and self-learning can help you develop these skills but the class will get you there much sooner and safer. If PADI, TDI or GUE can get you here, great.

You can still get yourself into significant amounts of deco (and trouble) between 100-150'. It's always a good idea to build on that progressively to see how your body reacts to decompression, progressively deeper depths and narcosis. In the Great Lakes cold is a factor. Are you prepared to do an hour of decompression in 38-40f water? Appropriate undergarments, active heating? How does your body react to 30 minutes of decompression? Are you more susceptible to DCS than others? How do you feel/react at 150' of 38f water?

When you start getting into the normoxic trimix range it's not unheard to have upwards of an hour+ of decompression time staring at you in the face. Not a good idea if your longest decompression dive has only been ~20 minutes.

Onto your original question:

I'm wondering whether AN/DP (or the equivalent PADI courses) provide a certification and skills that are useful by themselves for real dives, or if they are better understood as stepping stones to trimix certification.

They are absolutely useful by themselves. Getting comfortable carrying stages bottles, switching gases, holding decompression stops, planning dives/tracking gas consumption, lost gas plans, decoing on backgas, tracking OTUs/CNS, building experience at depths (100-150') with real decompression.

Also, having access to O2 (or even 50% for that matter) to do decompression at even recreational dive depths provides a huge advantage. Maybe you already do this? I don't mean to make assumptions but a card will make it easier for some boat captains and insurance to digest.

A lot of us take for granted that we can punch some numbers into MultiDeco and have it spit out a a master plan for us to follow or strap on a couple Shearwaters and go diving. Truth is neither of these prepare you for going through the motions and actually executing the dive.

I can punch a plan into my Shearwater for 350' dive and the numbers can look good; It doesn't mean I can safely execute without some significant build up dives.

 

[PfcAJ]

How would handle a lost gas?
Team deco? It would be impractical to carry enough bottom gas to do deco on it in case you lose the single deco gas. And usually you find out when you need it!

cheers

Run the numbers. Min gas and the amount of gas you need for backgas deco on a tech 1 dive are the same (or nearly the same).

 

[PfcAJ]

ik im just fundies certified but how would you plan a strict tech1/cave2 dive, as in bringing only 50% and not allowing anymore than 30min of unadjusted deco? also as the diver gets more experience and extends their bottom time in the deeper caves couldnt they bring stages along a bottle of O2 (both of whicthey got from their cave 2 card) with their 50% bottle instead of waiting to get tech 2 certified? i get that theres no scuba police to stop someone, but if the diver slowly adds on the complexities i dont see the big deal imo.

Deco gas choice depends a lot on depth.

If you're looking at using two deco gases you really need at step up and take tech 2.

 

[2airishuman]

Also, having access to O2 (or even 50% for that matter) to do decompression at even recreational dive depths provides a huge advantage. Maybe you already do this? I don't mean to make assumptions but a card will make it easier for some boat captains and insurance to digest.

Just to be clear, I have never made a dive where I exceeded NDL, and I have never dived with mixtures richer than 40%, nor do I plan to without taking first taking AN/DP or an equivalent class.

I do dive a twinset, or a stage, or sometimes both, either for extended runtimes in shallow water, or for redundancy when solo or without an experienced teammate.

 

[macado]

Just to be clear, I have never made a dive where I exceeded NDL, and I have never dived with mixtures richer than 40%, nor do I plan to without taking first taking AN/DP or an equivalent class.

I do dive a twinset, or a stage, or sometimes both, either for extended runtimes in shallow water, or for redundancy when solo or without an experienced teammate.

I didn't want to make any assumptions but I just wanted to state that I find carrying deco gas to be very useful even on modest recreational depths. Having access to richer gases (>40%) for decompression (part of AN/DP training) is very beneficial.

 

[beester]

How would handle a lost gas?
Team deco? It would be impractical to carry enough bottom gas to do deco on it in case you lose the single deco gas. And usually you find out when you need it!

cheers

Like PfcAJ said, next of course their are lost deco gas scenarios (within team) that allow for contingency which is trained during the course.

 

[kafkaland]

I have already chimed in in how valuable this course was for in terms of mindset and methods. Where I'm having the most difficulties, though, is finding buddies for dives at that level. Most who take AN/DP seem to move on quickly to normoxic trimix and don't appear to be too interested in doing let's say dives to 120' with 20 minutes of deco on O2. It reminds me a bit of when I was at the Intro Cave level. It was very hard to find buddies, but at Full Cave the buddy universe opened up significantly.

 

[Jack Hammer]

Would you mind giving some examples of info not covered in AN/DP that was covered in Fundies?

My class was in 2009, its been a long for me to recall all the specifics. Basically Fundies was more in depth toward gas management and planning. The deco reading was better. Situational awareness was more involved. As were the rescue procedures, including bringing an actual diver up from 20' while maintaining control. In AN/DP you just needed to to show you could do a skill, even poorly while bobbing up and down. Fundies you actually needed to do them well while maintaining control and show it repeatedly.

Basically I came into Fundies thinking I didn't need the class and was gonna skate through because i was a tech diver, had been diving with a stage and deco bottle and knew all the material and could easily do the skills... I was extremely mistaken.

 

[Centrals]

Humm, Deep Air and trouble remembering, could there be a correlation?

Tobin

No issue at all for me personally.
PSAI Narcosis Management to 73m could be different.