The usefulness of deco training without trimix

[AJ]

If you are looking into deeper and more deco I would do a normoxic tx (and not a deep air/extended range) kind of thing... but maybe I'm a bit silly at that.

You're not the only one. I don't like to do deep dives on air. So for me it woiuld also be a stepping stone. Usefull, but not usefull to me without further training. I'am not saying it's not a usefull training for others, it can be if it fits your style of diving.

 

[kafkaland]

I was for a long time wondering the same as the OP, as I live in Michigan and dive mostly wrecks here, as well as the caves of Michigan. Then, after bumping up against the NDL too often, I finally took AN/DP here locally, and it was very much worth it.

The biggest benefit for me was that it's liberating. It's no longer the tyranny of that NDL number that matters above all else, as we were taught in OW. It's about the ascent schedule for a given dive, the conditions, and your risk tolerance. The bright line becomes permable, as you now know the considerations that go int crossing it. And if anything, I have become more conservative in my NDL dives, running the profile said on some dive software ahead of time and add that minute at 30 or what have you. I also appreciate having O2 available, especially for the caves. For the Great Lakes I am still not going below 130 even thoug the cert is good to 150, as I get sufficiently narced at these depth. And what good is a dive I feel you don't remember half of it?

I didn't jump right into Helitrox for practical reasons, although I would have liked to have that option. First, it would require a separate drysuit inflation system, which I don't have and would add another layer of complexity right there. Second, many training sites here don't have helium readily available, so the logistics were difficult. I am planning on doing normoxic trimix soon, but before I do that I'll practice with the second deco bottle a bit in the local mud puddle. With one, I'm reasonably fluid, but two will be another step up.

 

[RyanT]

And one more vote in favor. AN/DP is a really great set of courses. You'll learn a lot and it will make you a more competent diver. Its also not hard to do some real decompression on a 130' dive.

 

[tomfcrist]

Concur with the previous replies.
AN/DP is probably the most enlightening course you will ever take if it's taught correctly. The skills taught and the mindset taught are the foundation for more advanced courses, but even if you have no intention of diving caves or Trimix etc...you should leave with some insight on how to be a better diver overall.

 

[boulderjohn]

Whether you choose to do TDI or PADI, the courses are valuable in themselves whether you go on to trimix certification or not. I do a lot of tech diving in South Florida, and a lot of the more popular dives are in the ranges of these classes. For example, probably the most popular of these dives is the Hydro Atlantic, the deck of which is at about 150 feet, and the sand is at about 170 feet. PADI's Tec 50 class has a maximum of 165 feet, so that dive is perfect for it. I choose to do it with trimix, but lots of people do it on air or very light nitrox.

 

[stuartv]

I am starting to think about taking some tech training as a step towards my goals of wreck diving in the Great Lakes.

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.

Much of the question revolves around whether or not there are dive teams, trips, and LOBs organized to work within the relatively narrow depth range where decompression is required but trimix is perhaps not.

The key is that any dive (past about 40') can require deco stops, if you stay down long enough.

I have Helitrox certification. But, now that I've done some dives using it, I don't find that helium is worth paying for at depths of 150' or less. But, I have done some nice long dives at depths less than 130' thanks to being able to carry a deco gas and do the stops on the way up. I did a dive a few weeks ago on a wreck where the sand was 135'. My average depth during the bottom phase was right around 130'. I took a single AL80 of deco gas and had a bottom time of 47 minutes. That was a nice dive (for me, anyway).

The hard part seems to me to be getting on a boat where it will be acceptable to do those longer dives. If it's a boat full of people doing NDL dives, they are not going to want to sit around waiting for you to come up after 30 minutes (or more) of deco. For those kind of boats, AN/DP is still somewhat advantageous. You can make a point of getting in first, stay down until the last diver is starting up (where you are now a few minutes into deco and they aren't), then follow them up, do your stops, and use your deco gas to get yourself out of the water at the same time as the last of the NDL divers. You get maybe 5 - 15 minutes of extra bottom time and still get out with "cleaner" tissues than if you did a normal NDL dive.

 

[KenGordon]

I am starting to think about taking some tech training as a step towards my goals of wreck diving in the Great Lakes.

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.

Much of the question revolves around whether or not there are dive teams, trips, and LOBs organized to work within the relatively narrow depth range where decompression is required but trimix is perhaps not.

Come and do Scapa Flow. Those are real dives.

There is plenty of diving where backgas deco on twin 12s of an appropriate Nitrox mix works well. A bit deeper and the weaker mix makes backgas deco very tedious, so a deco stage is sensible.

In scapa last year my buddy only used helium on one dive (44m) at a cost of £80. But the deeper (>35m) dives end up as deco dives. On a rebreather, I used trimix for everything. Similar in Shetland, although I did have a buddy with 7 minutes of stops on a scallop collecting dive because of a long and deep earlier dive, a poor choice of gas and a long time spent with an octopus.

Once you start carrying enough gas and there is a lot to see (like a whole battleship) then deco follows. It does not need to be terribly deep.

 

[tomfcrist]

Stuart,

Not to be critical, but the only way you are getting out at the same time as an NDL diver with "cleaner" tissues is to have extended your deco well beyond being "clear".

Either way, most boats don't mind if you are doing limited deco(10-15min total)...as you said, be the first to splash and the last to get back on the boat.

 

[stuartv]

Stuart,

Not to be critical, but the only way you are getting out at the same time as an NDL diver with "cleaner" tissues is to have extended your deco well beyond being "clear".

When I was doing recreational diving with my recreational computer, I would typically stay down right to the last minute or two of my NDL. My recreational computer runs the DSAT algorithm. That generally gives NDL times that are roughly equivalent to Buhlmann ZHL-16C with Gradient Factors of 90/90 or 95/95.

Now, I dive with GF 50/80. So, someone who is using DSAT, doing an NDL dive and getting out, is getting out with a surfacing tissue pressure gradient (in their leading compartment) of 90-ish percent of the M-value of that compartment. I do my deco and get out with a tissue pressure gradient of 80 percent (or less).

I do believe I am correct in saying that I am getting out cleaner than an NDL diver who is using DSAT (which is a pretty commonly used algorithm).

 

[seeker242]

I think that a AN/DP cert is a nice stepping stone...

You get used to some of the same procedures used in any of the follow up classes taught,

How does it compare to GUE Tec 1? Is there any crossover as far as procedures go?