OUT OF AIR - Last ditch effort breath from you BCD

[Sideband]

I'm very new to diving in general, but one issue I didn't see addressed in this thread is the ability to actually inhale a lung full of air from your BC when that air isn't pressurized as it is in your tank. Can it even be done is my question, and if not, isn't this a moot point? Personally I prefer the "always have 500 pounds" rule as most likely to keep you out of trouble.

I don't think it's a good idea, but of course it's possible (assuming there is a lung full of air in the BC). If it wasn't possible you wouldn't be able to just push a button and dump air from the BC at depth either.

Joe

 

[SteveAD]

breathing out of a bc is like prayer there will always be those who have done it and claim it saved them, but it is impossible to say they would have died without it. avoid going ooa

 

[Lead_carrier]

Are you familiar with the incident that killed Sheck Exley? His tanks contained over 900 PSI when retrieved, but at his max depth (over 900') they were at 0.

Just a bit. I know that no one was with him so they don't know what his guages were reading. If you have access to any articles that I can't find I'd really appreciate a link to them.

To quote from the article Eulogy for and Explorer " Later, the members of the team published a detailed analysis that concluded Exley probably fell victim to "HPNS, oxygen induced incapacitation or a convulsion" or some combination of those events (see www.iucrr.org/aa_misc.htm). Both of Exley's primary tanks were exhausted, as was one of his two side-mounted tanks (the other was untouched). The team conjectures that for unknown reasons Exley ran out of gas in his primaries and was forced to switch to the side-mount "travel mix" that was far less appropriate...."

 

[dherbman]

Just a bit. I know that no one was with him so they don't know what his guages were reading. If you have access to any articles that I can't find I'd really appreciate a link to them.

Incident report

My initial post indicates the surface gauge pressure was 900PSI. That was not correct, it was 500PSI.

 

[Sideband]

Incident report

My initial post indicates the surface gauge pressure was 900PSI. That was not correct, it was 500PSI.

That would bring him out of the 2000' depth range and a lot closer to the 1000' he was 'actually' at.

Joe

 

[Jim Ernst]

As other have pointed out... we breathe air due to the "tension" (difference) between the ambient pressure and the tank pressure. You have a TOUGH time breathing on a snorkle that is longer than 18 inches because the air in your lungs is at 1 atm while the ambient pressure surrounding your chest at 18 inches is 1.045 atms which is less than a single PSI.

If the pressure OUTSIDE of the tank is 4atm, then you can not breathe your tank LOWER than 4 atms. However, bring it up to 33 fsw (2 atm) and you now have a 2 atm tension (4 atms in the tank and 2 atms outside). Breathing is now possible until you breathe down the tank to the ambient pressure again.

This is why we teach students to KEEP their regs in their mouths! You don't want to waste ANY air trying to clear the regulator so KEEP IT IN!

For those of you who have taken up the sport within the past 20 years, remember that for MANY of us during the 70s, running out of air was the way we ended our dives. We did not OWN an SPG or a depth guage for that matter. When we felt the "pucker" we would reach back and trip our J-Valve for a couple of hundred PSI to get to the surface. Often, we would find that the J-Valve had already been tripped and we just had to KICK HARD to the surface. Even then, we could always count on at least one breath on the way up.

nice post doc!! i found your info interesting and informative, also that diving back years ago , it sounds like you had to be ready to be diving by the seat of your pants so to speak, as i have only been diving two years now and could not even imagin diving without an SPG-DEPTH GAUGE.

 

[cummings66]

What does this mean exactly? 500 psi is hardly gone in a blink of an eye but I am unsure what you are trying to say here. If I am on the surface with 500 psi....seems ok to me.

A bit late and I'm sure somebody said more about it. I have been at 30 feet with 1500 psi with a diver in an ooa. I donated it to him. We were on the same dive and profile, it's just that he used more air. So I gave him some air and 3 minutes later I have 500 psi left. Now I don't know what he did with it, but it went fast. If I had 500 psi and he was out, within a minute I would have been ooa.

That's what I mean by it being gone in the blink of an eye. A diver who's ooa will usually suck air at an unbelievable rate and you had better have more than 500 psi when you give it to him or you will run out.

Gas planning is about ensuring you and your buddy have enough air to get to the surface if one or the other runs out. If you plan to reach the surface with 500 psi you left out the buddy and his using your air. You will hit the surface with more than 500 psi most of the time if you consider your buddy, unless you hang around 15 feet for a time in which case it's not the same amount of air that you need to reserve.

 

[cummings66]

It was stated earlier, but it may be buried in the bunch. When your tank starts to get low, it becomes more difficult to draw in a breath. While uncomfortable, you will have about 4-5 normal breaths left depending on how you breath. Time to head up.

Not all regs act that way. Some of them like mine breathe as easy on the last breath as they do the first. Test it under controlled conditions and you may see. Now some regs like the Brute are as you describe.

 

[Sideband]

I believe that is the difference between a ballanced and unballanced first stage.

Joe

 

[Lead_carrier]

Incident report

My initial post indicates the surface gauge pressure was 900PSI. That was not correct, it was 500PSI.

Thanks.