OP
I don't know how the standards compare for BSAC SMG and BSAC DL + ADP. But, it they are identical except for the classroom coverage of Physiology and Planning and the in-water skills required are the same, then yes, it does seem like you should have been able to get the SMG with only classroom. However, I doubt all the standards, including in-water, are identical, save for 2 chapters of the book, so the question is probably moot.
Or perhaps you are saying something different than the rest of the replies here. It seems like you're actually suggesting that the use of 20% Helium, down to 45m, DOES require a higher level of in-water skill. Is that it?
Another thing I thought to point out is that, as an example, the Oceanic family of computers that has the DSAT algorithm (e.g. Atom, Geo, etc.) is significantly less conservative than any tech diver I have seen. Tech divers generally seem to agree that diving with GF 99/99 would be crazy. But, I have compared the NDLs in the Atom 3.0 manual to what you get when doing a dive plan in Multi-Deco or planning on a Petrel. The Oceanic computers set to use DSAT and no Conservatism Factor produce NDLs that are VERY close to what you get when planning with Buhlmann (ZH-L16, but I can't remember now if I used B or C) and GF99/99.
So, in terms of the risk of getting bent, it seems like any ordinary Rec diver with an Oceanic computer is more likely to get bent than somebody who has full AN/DP training and then has a classroom session/exam and starts using 20% He on the same dives they're already doing.
So, seriously, how realistic are the concerns about getting bent from starting to use 20% He after AN/DP plus a classroom session for the He? Surely one would expect that a diver with AN/DP certs and even diving a liberal GF High of 85 would be less likely to get bent using 20% Helium than a Rec diver with 4 OW dives under their belt, diving a computer that is the equivalent of GF 99/99, using a big tank, and staying down right up to their NDL (as I was doing last Summer with only 30-something dives in my log - it's not that hard, even for a new diver)?
Or, as I have already asked to a resounding silence, what would be the actual argument to TDI to stop them if they announced a change to the standards to make Helitrox have prereqs of AN and DP and then Helitrox is classroom-only? What risks are there to be genuinely legitimately concerned about?
The increased risk of getting bent? And what is the real magnitude of that risk? Is it about like the chances of getting blown off a wreck and having to do a free ascent? Or is it more like the chances of losing all your deco gas, and losing your buddy, and getting lost and having to do a free ascent?
I'm being sincere. It seems like the increased risk of getting bent when diving to 45m and using 20% Helium would be dang near negligible compared to doing the same dive with the best mix of Nitrox. But, I realize I'm extremely inexperienced, so if that's wrong, someone please explain it to me. @KenGordon, you referred to the physiology of Helium and said that shorting yourself 1 minute on Helium is worse than 1 minute on Nitrox. But, the reading I've done on deco makes me think that the risk really is pretty dang near negligible - in terms of the increased likelihood that you'll get bent because of it. As in, if you get bent, you would likely have gotten bent anyway. If you weren't going to get bent anyway, then you probably won't get bent because you had 20% He instead of an extra 20% N2. And it might all be offset by the extra clear head making you less likely to screw up your ascent in the first place. The extra clear head saving you from mistakes on the bottom definitely seems likely to skew the overall stats for getting hurt in favor of being able to use the Helium.
@KenGordon, do you honestly think the decreased safety of Helium's less forgiving deco is a bigger downside than the increased safety of being more clear headed?
