Air hog

[BRT]

300 psi will not allow a diver to bring somebody else up on his octo . . . at least, not from anything other than the safety stop! If you do the math, the minimum gas reserve to bring two divers up from 60 feet, assuming a 30 fpm ascent rate and omitting the safety stop, is between 6 and 700 psi in an Al80. So one should definitely be ascending by the time the tank reaches that point. It's generally taught that min gas is always at least 500 psi, simply because of the inaccuracies in pressure gauges in the lower part of their range. I have certainly seen gauges be as much as 200 psi off.

Assuming that as you near the surface you can breath down to 100 psi tank pressure, and assuming you know your gauges are working, 2500 psi is 64 cu ft (to 500psi) of a full AL80 (77 cu ft). So if one person can get 60 minutes out of 64 ft2 at an average depth of 30 ft that would be 1.07 ft2/minute 2 people can get 30 minutes out of that same 64 cubic ft at the same average depth or 2.14 cubic ft./minute. Each 100 psi of the AL80 is 2.57 cubic feet. 200 psi should get 2 people to the surface with just enough residual pressure to be able to breath in the last 10 feet. Bad idea? Of course. On the other hand if my buddy and I somehow end up in 60 feet of water with 300psi between us we are going to ignore 30 feet per minute and be at 15 feet in a hurry. Twice I have seen divers blow through their air in 15 or so minutes at 100 ft. and when the looked at their gauges they were at 300psi. They both made it up safely. Poor divers? Yep. One was a divemaster trainee and one was a genuine PADI Rescue diver. But it didn't take either one of them very long to go up once they noticed their gauges. I just think this minimum air standard is overdone for recreational divers. I'm all in favor of leaving the 60' bottom at 600 psi but when they start telling me to be back on the boat with 700 lb I kind of revolt.

 

[dumpsterDiver]

There was a thread a while back on exactly this topic. I agree will all the responses, though have never seen this happen myself yet. My wife says I've led a sheltered life.

I made a quick video of it once, when my son (13 or 14 yrs old) and I were trying to conserve his air on an 80 ft dive.

I think it is excellent practice and the dreaded air 2 didn't kill me!




[video=youtube;vDrF1AOnabc]https://www.youtube.com/watch?v=vDrF1AOnabc[/video]