Breathing directly from a tank at depth

[muddiver]

In commercial dive school we had a "free for all" day in the training tanks during open house day. One of the guys thought of breathing off of the 1/4" hose used to take the divers depth reading. It is fed off of a needle valve so you can control the volume coming out of the hose. I doubt that teh pressure was much over 20 psi but it was a real pain in the ***** to take a breath off of it.

Using the standard heavy gear helment without the suit or breast plate was a blast. You could turn it over and let it fill with water, then done it like a motor cycle helmet and it would purge it self while you watch from inside.

 

[SNorman]

I could be wrong, but here is my thought process on this.

As you get deeper you would need to ensure a tighter and tighter seal (from not really needing any seal near the surface) to be able to breath in any of the air. I base this on a simple experiment. Take a hose and try to breathe through it when you are 5 or so feet under the surface and it isn't too hard. Try and breathe through it at 30 feet and you are gonna struggle more. As you go deeper your lungs (an airspace) are compressed and therefore you need more air pressure to overcome the resistance to breathing created by the outside water pressure. This is what your reg does automatically for you.

Doesn't this work the same for trying to breathe from a tank? Wouldn't you need a better seal as you go deeper so that you can build that pressure to a point that it will overcome the outside pressure. I can see doing it under about 40fsw or so (depending on the strength of your lungs, but would it be possible much deeper if you don't get some kind of seal?

If that were true, it would be just as difficult to get air with a 2nd state reg in place. The 2nd stage *lowers* pressure from IP in the hose to match surrounding pressure, it doesn't increase pressure or suck air from the tank to make breathing easier. The function of the 1st stage is to release air that is around 150psi over ambient pressure.

Does anybody know the exact depth limit where your body just cannot physically breathe air at surface pressure? Most people say they can't do it past 3 feet. At 2 feet there is something like 250 pounds of pressure on your chest, so it's like breathing with a very large man sitting on you

I think it depends on how you measure, too. Do you measure the depth to the top of your head, or to your lungs?

 

[Walter]

Nyet. But I did like your reasoning.



5 foot depth is really really very hard. 30 feet aint happenin.

Neither is 5 or even 3.