More on CESA

[perpet1]

Is this a trick question?

Other than the obvious spelling mistakes it was not a trick question at all. My point was simply that most people believe empty = 0psi. But when you are down say at 99 feet empty is typically the point that you can no longer breath off your reg. The two are not the same.

When you are down at 99' the external pressure is about 60psia. When your tank pressure drops to about that you will not be able to breath off of your reg give or take. So as you go up the external pressure decreases and more of the air in the tank becomes usable so empty does not mean 0psi.

So lets say you breath a tank down to the point that your reg will no longer provide air --say 0psig @99'. That means the absolute pressure in the tank = that absolute enviornmental pressure surounding the tank --60psia in the tank, 60psia outside the tanl, 0psig between the two @99'. So move up to 33' in the tank you will still have 60psia BUT only 30psia outside the tank so 30psig that is usable--air to breath. so you ask how much is 30 psi? More than enough for a breath--about .75ft3.

 

[boulderjohn]

Buddy breathing was only described in my own OW training, so I did not actually practice it until my DM class. I was surprised at how hard it was for even experienced divers to do it well. With a little practice, my buddy and I did the exercise well, but we were both respectful of the difficulty of the task.

I have heard some stories about practices that did not go well. I have heard people tell me about the sense of panic they felt when a buddy decided to take another breath, for example. I have heard about near drownings and struggles for regulator control.

On the other hand, an insta-buddy I found on one dive trip, whom I will politely describe as an idiot, told me he was solo diving without special equipment when he ran out of air at 75 feet. He did a CESA the entire way, and he said it was no problem because of the rapidly expanding volume of air.

Consequently, in an OOA emergency, I would only attempt buddy breathing with a buddy who was highly skilled and with whom I had practiced. Since I am a single diver who has to look for an insta-buddy on almost every dive trip I take, you can be sure that if I am ever OOA, I will be doing a CESA with confidence and without hesitation before I would even consider buddy breathing with a stranger.

 

[kalvyn]

Time after time we keep saying these are safe WITH PROPER TRAINING AND A PROPER MINDSET!

<snip>

Unless you are/were a submariner or military diver you don't have a clue.

Sorry, I'm joining the party late... just logging on here for the first time an a few days.

Ironically, I was discussing this very topic this past Sunday with an ex-Navy submariner. He said that they regularly did CESAs from 110' as part of their training, wearing nothing but a 'Stinky Hood' (Google it... I had to ). He also said they had divers in the water to slow their ascent, to help prevent DCS. Obviously, in a real bail-out, the divers wouldn't be there to slow your ascent.

He also said that the Navy regs said that you could survive doing a CESA in this manner from 300' to 400', though there may be "complications". :11:

I agree with Gary's point here - different applications from different disciplines. I know I, as a sport diver, wouldn't want to do a CESA from 100'. I make sure I dive with folks that I know will be able to properly respond in a crisis at that depth. If I am diving with a 'buddy of circumstance', I'll change my dive profile accordingly. For me, a CESA is the last option before drowning; I hope to have the situation well in hand and on my way out of the water in a safe and controlled ascent with my buddy. I guess only time will tell, though.

Jimmie