There were some very constructive comments in the last threads (although I've only seen the nice, moderated versions
) so I'll avoid the who-said-what-and-when and instead focus on these parts.
Of course gas has to be vented. Duh. You're ascending. If you were doing so OOA, you'd still have to vent gas from your BC. Whether you're breathing it, or rebreathing it, somehow some gas has to go in the water.
Excellent. Agreed. This is the first notion.
1. You are completely unable to get gas from your air supply, and I'll posit a catastrophic failure of some kind, because I agree that if you are simply "out" you're really not, and will get one or two breaths during the ascent from the tank.
I agree on all of this too.
2. You are at some degree of depth, and have some volume of gas in your BC.
Okay, agreed.
I have already said (more than once) that the PREFERRED situation is to BREATHE the BC, not REBREATHE the BC. That is, you inhale from the BC, and exhale into the WATER. This accomplishes both giving you some gas AND venting contents as you ascend.
Yes, agreed.
I have further pointed out that even in one of the most conservative of situations - that of a very thin wetsuit - you have at least four full breaths without rebreathing the BC between 99' and the surface.
Yes, you've made strong logical case for it and I concur.
I am NOT arguing, Pete, that one should not attempt to get gas from their reg/tank in such a situation. I am arguing, however, that if you are OOA and have determined that your reg is useless (e.g. the aforementioned LP blowout or first-stage lockup) then why would you just consign yourself to death or an ESA without using all the available gas sources?
Yes, I agree
that in the (highly unlikely) event that your regs are absolutely useless (and you're diving without any redundancy) the BCD is the last option to go. This is the major notion for this scenario.
It was for a dogmatic refusal to consider a perfectly viable gas source as available to you for that emergency ascent.
No, I'm not dogmatic, I'm pragmatic. Under the notions and positions expressed above, I agree with your choices and would do them myself as I'll exemplify below.
Since about half of the DAN accidents reported arise from OOA events, it seems obvious to me that telling people not to consider such a gas supply in an emergency is crazy at best.
Ah, no! :banging:
Here we're back to the track which has led me to contest so many notions previously in this thread, and with good reason. Please let's not go back on this route! :nono:
You see,
by far the greatest majority of those OOA:s is user error, diver not paying attention to his or her SPG, not maintaining his or her equipment etc. Which is what NetDoc has argued all along.
I have concurred and consistently opposed practicising something which in itself is dangerous to prepare for an event so unlikely that it probably won't happen in any of us debaters' or readers' diving careers.
Therefore - and this give those of us still pursuing logical arguments in this thread a chance to find common ground and round-off the thread on a nice, constructive note - I would postulate the following summary:
(1) If there is absolutely no other way of getting air, the BCD is the last resort, using it the way Genesis has outlined in his last threads.
(2) The likelihood of the attentive OW diver ever having to do this, however, is very small because:
- most OOA:s by far are due to user error and easily preventable
- the buddy system is redundancy-at-hand taught already in OW class
- there are far better and safer ways of ensuring redundancy for more advanced dives (and the likelihood of simultanous LP hose blowout on all redundant air sources is nil)
I'm willing to close on this note and exemplify by a personal example:
When diving my single tank rig, I always know where my primary redundancy and spare brain, my buddy, is in all waters - I will in fact end the dive if I lose my buddy - and I expect to be able to regain the surface even with a freeflowing reg (which BTW is not as unlikely as an LP hose blowout under water).
But in the highly unlikely event of simultaneous loss of dive buddy and catastrophic gas loss in my rig, yes, I will certainly breathe the BC and vent into the water on my way up kicking hard. You bet you I will! I'll do anything to live ...
NOTE: At the surface I would very likely drop my weight belt because of the exertion inherent in getting there!!! (I think this is an important point not made so far in this thread - remember, in dive fatalities, many divers have died after regaining the surface).
(With my twinset, the above is not necessary under any circumstance. With a rebreather things are different again and the single tank rig situation doesn't apply.)
I think this covers all bases. May I just end by saying that I never enter into arguments like these for arguments' sake. I have no particular drum to beat and no private agenda to pursue. My only agenda is dive safety (at which I am admittedly anal) and I will pursue a thread where I believe inherently hazardous or even dangerous notions are introduced until a reasonably safe consensus has been hammered out.
I hope, trust and believe the latter is the case right now.
eace:
EDIT: typos, clarity and highlighting the drop the weight belts part.
