Absolutely, I agree. But that's something that the boat captain would be responsible for, and there should be a lot of O2.
Emergency O2 would need to be more than just a single 40 CUF deco bottle, which might well be empty if it was ever needed on the boat (after a dive).
I was just saying that while a small backup 100% O2 source might come in handy on occasion, I don't think that the possibility that your deco bottle could be grabbed for that purpose is a reason to chose to dive 100% over 80%, all other things being equal.
If I am doing a tech dive with my dive buddies, we are not counting on the boat for much beyond a good drop --hopefully we will have them overhead when we reach our 20 foot stop....but we would have already had a good dive, and we'd be happy.....
But seriously, once back on the boat, if we needed O2, we are going to KNOW that we have plenty for one or more divers in our group if it was needed, and that we are not relying on the boat for this---any more than we would show up on a boat expecting them to have tanks for us( with our not having warned them of this expectation)....So we would have several spare bottles of 100% O2, and how many spares would be based on how many tech dives we were doing that day, and how aggressive the profiles. Sure dive boats have their DAN kit for recreational divers...I think a tech trip requires more O2, and more involvement in planning for contingencies than is going to be practical to expect from recreational divers...thus we bring what we want...
Not to mention, while this has never been something I felt compelled to do, I have had friends that completed deco, felt normal, got back on the boat, and then decided that after an air break, they would do another 10 minutes of 02 at their seat on the boat, to clean them out faster, better, either for an extra safety margin from a serious dive....or, so that they would be better offgassed to do active things in the afternoon--or even additional dives.....Cleaner is cleaner. 100% works for this, 80% is defective for this intent.
And since everyone in this thread is enjoying/expecting some 90's DIR humour....
......Of course I would NOT want to use 80/20 -- as being seen with this on a boat, is too much like wearing a "Kick me " sign on your back, proclaiming to one and all that your a stroke and proud of it !
* Disclaimer* The last point, while intended for humor, actually gets closer to the issue than most would think....the reality is that the choice of 100% versus 80%, for most dives we would do, is more like a fashion statement---some of us wear Polo shirts, some wear funky sandals, etc...each of us drops themself into a stereotype when we make certain choices...which camp do we want to appear to be in.....For most dives, I think this is really the difference.
For the really extreme, or for repetitive tech dives in same day, the surface O2 with breaks actually would be hard to argue with....then all you have to do is argue about whether you should be doing the repetitive and aggressive tech dives in the same day...
