dumpsterDiver
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In an Al80, 50 psi is more than 1 cu ft. The typical volume of a resting breath is about .5 liters. For scuba and breathing deeply as we are taught, lets call it 1 liter. 1 cu ft is 28 liters. WOB will be quite a bit higher if that is the last 50 psi in the tank, but it is there for the taking unless the restricted breathing leads to panic. 50 psi is about 30 breaths.
The pressure in a balloon is only slightly over ambient, like maybe 1 psi over ambient. Scuba regulator opening is a bit smaller but less than an order of magnitude. Scuba is using a longer straw but you could always go to your alt to shorten that - I doubt if it will make any noticeable difference.
The problem is the gas is there but it will be more work to get it. And working harder when you feel you are not getting enough will not help.
Yes,, this information is more aligned with my thinking.. you can figure roughly that you will use 50 psi per minute to hang on a safety stop, if you are really relaxed and trying to conserve air. This is a good rule of thumb.. so if your are low on air,you should know you can often still make a safety stop. 500 psi is around 10 minutes of hang time..
I am really not that knowledgeable about regulators, but some of the information provided here makes no sense to me. drain your tank down to a very low pressure, hook a reg up and breath!
I think you will find that you can continue to sip air slooowly from the tank for a while. I don't believe any of this 130 psi tank pressure means you can not get air from the reg.. Try it yourself. Press the purge instead of sucking and you will get air, without effort for quite a while.
I'm not saying you should run your tank down super low, but some of the information on this thread would lead a diver to assume that terrible things will happen with a low tank.
I used to golf ball dive and often could not see the gauge. I would know when the tank was getting low, because it got hard to inhale, but I could make my way to shore and even along shore for quite a while and when I got out, the tank would be MT! Did it many dozens of times.. And I never got water in the tank either.. just shut the tank down when the pressure gets really low..
Also, the idea of being on the boat with 500 psi is incredibly stupid.. uniformed divers will rush their ascent in order to make it to the boat with 500.. A much better rule would be to leave the bottom with XXX psi.. whatever that figure is, should make sense, but demanding 500 psi reserve is really treating people like imbeciles.