How much air for a CESA

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Thanshin

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Location
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You're 100ft deep in a 12l tank, you're OOA and your buddy is nowhere to be found. You start a CESA, exhaling slowly and breathing the air your tank gives you as the pressure lowers.

It the following correct?:
- At 100ft an OOA 12l tank contains 46 liters of air.
- Every 33ft you go up, it gives you 12l of air.
- With deep breaths, taking into account you have to be careful with overexpansion, you'd get about 4l in each inspiration.
- So, you have about nine deep breaths to go up the 100ft to surface. (which looks like the perfect argument to explain someone that even in OOA there's no hurry to sprint up and die on the boat).

[Edit: No, it is not correct at all. As pointed by ErikH, you only get those 36l of air when you don't need them anymore. On the surface. At 66ft you do get 12l but you breathe them as 4l.

And, if you take some air in the path to 66ft it's even more "expensive".

In all, maybe there is reason to try to hurry a bit to the surface. An OOA at 100ft might not be the best moment to take pictures and practice your SMB deployment.]
 
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A 100cf tank is plenty for a diver to conduct a dive
 
The rest is BS
 
Like discussing bounce with an 80
 
A 100cf tank is plenty for a diver to conduct a dive
The rest is BS
Like discussing bounce with an 80

I've tried to understand you, but it's like reading sacred text. In a lost language.

100cf is a 15l, right? No idea of what does that have to do with the question though.
What rest? Everything is the rest?
Bounce with a 80?

Nope, sorry. Maybe I need a coffee to understand that.

Or LSD.
 
I've tried to understand you, but it's like reading sacred text. In a lost language.

100cf is a 15l, right? No idea of what does that have to do with the question though.
What rest? Everything is the rest?
Bounce with a 80?

Nope, sorry. Maybe I need a coffee to understand that.

Or LSD.

Keep your reg in your mouth and be prepared to turn your "CESA" into a "CEBA".
 
I think 100 cf is 12L - see http://www.scubaboard.com/forums/ba...psi-bar-scuba-tanks-rmv-sac-calculations.html
You're 100ft deep in a 12l tank, you're OOA and your buddy is nowhere to be found. You start a CESA, exhaling slowly and breathing the air your tank gives you as the pressure lowers.

It the following correct?:
- At 100ft an OOA 12l tank contains 46 liters of air.
- Every 33ft you go up, it gives you 12l of air.
- With deep breaths, taking into account you have to be careful with overexpansion, you'd get about 4l in each inspiration.
- So, you have about nine deep breaths to go up the 100ft to surface. (which looks like the perfect argument to explain someone that even in OOA there's no hurry to sprint up and die on the boat).
Well, you can debate the variables about how much expanded air you get at various depths on ascent vs how much you use when you inhale at various depths, but I'll tell you from my experience - it didn't work for me...

We were about 100 ft down with me following my bud as he followed the DM thru swim thrus and I tried to signal him 3 times that I was getting low before accepting that he was going to ignore me and follow the DM - so I left him in the DMs care and bailed with a few hundred psi in a 100 cf tank. I really don't remember the specifics as narcosis and excitement were in play, but I did have air left - just not enough to make the surface. I had to switch to my pony before the SS. We later had a discussion about the signals we'd practiced in the past, but were missed that time - and I wonder if I should have tried to grab him, but the swim thru he was approaching was tight and he was in good care with the DM, so I called it best I could.

Another trip, I actually screwed up and did a CESA from 50 ft on a single 80 cf, no pony - but for that ascent I did hurry more, but ran out of lung air at one point, stopped to breath in from newly expanded air, then continued up exhaling.

If anything, you can learn more from my mistakes than what I get right - so make of that what you will, but if you hit zero on your spg alone at 100 ft, I suggest you hurry your ascent - but be careful about inhaling while ascending. I stopped for that.
 
I try to share from my screw ups and how I survived them in hopes of helping others, but that certainly comes with a cost. Just try to avoid my mistakes.
 
"(which looks like the perfect argument to explain someone that even in OOA there's no hurry to sprint up and die on the boat)."

I think when you get negative feedback from your question it will be because of that last part.

If you have done everything else right, except of course run out of air, then a quick swim to the surface without holding your breath won't leave you dead on the boat.

Like Don said, if you want to figure out how much air you get on your way up, that's fine and fun, but should not really be factored into the emergency ascent.

Now everyone can carry on with the math...
 
How come you're running out of air, anyway?!? :confused: Surely you learnt, right back in Scuba 101, to check your air gauge - didn't you?!? And to start coming up at 50 bar (or approaching the red mark, whatever system you use)? You did, didn't you? Thought so... So why stop, just because you've done a few dives? The maths is irrelevant - watch your gauge, act your age, and stay alive!
 
https://www.shearwater.com/products/peregrine/

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