How Deep Can You Do An "Out Of Air Emergency Ascent" From?

[AquaTec]

Durring one of my training dive I was required to sit on the bottom at 100ft, take all my gear off including mask and fins. then ascend to the surface.

It was quite easy. I suppose you could mathmaticly figure out lung volume and rate of exhausting it and rate of ascent and then how soon you would just die trying it.

I would suggest avoid at all cost.

I too have thought about rebreathing my BC, yes hi in CO2 but also some O2 in there, I guess I say high CO2 because when I used to think about it the only method of filling it was with your bouth. so today it is filled with the air in your tank.

instead of exhausting it out as you surface why not suck it back
I don't know If i was in an OOA situation I would try anything.

Maybe I should start keeping my argon bottle at 21% I might be narced but I would have air

I have sucked a tank dry once or twice. this was before SPG and the reseve switch would get in the wrong possision. You definaetly whant to keep your reg in your mouth, and think about sucking a thick vanilla shake through a straw.

I am not a beleiver in dropping that weight belt unless I just took my last breath and I want them to find the body on the surface

Just a bunch of rambling thoughts with no meaning

I was on a dive this fall were a guy did it from 300 feet 98 meters to be exact. he set a new worlds record. I was one of the safety divers. Oh yeh he held his breath all the way down there too

warren I complement you on very sival responses, it makes for good reading

 

[Rick Murchison]

I'm pretty sure one could "make it" from 130 feet or better under most circumstances. The deepest I've ever practiced an ESA is 100' and it was quite comfortable.
My personal limit for diving without a fully redundant air supply is just over 100' - I will make brief excursions below that with a buddy, but if we're planning to spend any time at all below 100' it's time for the "H" valves or the doubles.
Rick

 

[Rooster1]

I think it depends if you ran out of air right after your last breath, or you just exhaled and now go for a breath and there is no air. I think if you were to get one last breath of air most people might be alright from a hundred feet. I need to work on that,
Very crucial is also the rate of exhaling on the last breath. you don't want to blow out all the air in one breath. I think that ahhhh they teach you in your ow classes has to be explained a little bit better as far as how slow that "ahhhh" should be. I remember during my check out dives when Iwas getting certified I had to do my emergency accent twice cuz I took a breath off the regulator before I reached the surface. I was exhaling too fast.

 

[jbd]

VTWarrenG--The reason I brought up the "excessive" bouyancy and the consequent increasing ascent rate is that it seems to me, from many of the responses and from my experiences from shallower water, that there is enough time to control the ascent rate. Granted as was mentioned you may want to boost the rate to 80' to100' per minute. The hope being that you arrive at the surface alive and without injury.

My youngest brother was literally rocketed out of the water from an uncontrolled ascent and did have a lung injury. My concern is to reach the surface safely in the situation at hand.

 

[rcohn]

Don't waste your time rebreathing your BC -- it's a very bad idea. If you have an OOA, spend those precious seconds ditching your weights and swimming hard, not fumbling with your inflator button.

I have absolutely no intention of being deep, with no air supply, and no buddy, so please don't worry about me.

Swimming hard is just plain dumb. You burn air much faster when working hard. Just relax and let your positive buoyancy carry you to the surface.

I believe you're confusing the technique of BC breathing with BC rebreathing. You're welcome to inhale from the BC's inflator, if, say, both of your regs fail (yeah, right), given that you then exhale to the water. The gas inside your BC is only enough for (at most) two adequately oxygenated breaths, and doesn't provide any real help in an OOA. You're also setting yourself up for a lung overexpansion injury or AGE because you won't realize when your BC is full during your rapid ascent. The overpressure relief valve on the BC has a cracking pressure far beyond what your lungs can handle.

Never rebreathe your BC.

First make up your mind. Are there only two breaths in the BC or is it overinflated? Even tropical BCs need around 6 deep breaths to fully inflate.

I'm aware of the DIR BC breathing technique, but this ascent started out with no air at all, so that isn't an option. Also the question was how deep can you go. We mostly agree that a fee swimming ascent will work from 100 ft. But what about 150, or 200, or even deeper. What about exiting from a short (obviously unwise) penetration?

I know someone who tried rebreathing a BC to find out how it would work. He was able to swim for at least 5 minutes. We all know this isn't a good idea, but if the choice is between dying and taking the risk of hypoxia or hypercapnia a drowning diver might want to know the techniqe is feasible.

The major broblem is that there is water in the inflator. If there is no air in your lungs you can't exhale to clear it. Attempt to inhale the water and you'll choke. The respiratory infection problem prevents this "skill" from being practiced making it extremely unreliable in an emergency. However, if a diver is foolish enough to get himself into a situation where he has no viable alternatives, BC rebreathing may be the only option.

You may prefer death, but others might select a last ditch option.

Ralph

 

[VTWarrenG]

Ralph,

Swimming hard is just plain dumb.

Good point. Let me rephrase: spend those precious seconds ditching your weight belt, not fumbling with your inflator.

But what about 150, or 200, or even deeper. What about exiting from a short (obviously unwise) penetration

OOA in those situations, without a buddy, will most likely result in death.

I know someone who tried rebreathing a BC to find out how it would work. He was able to swim for at least 5 minutes.

This is very surprising -- I don't doubt you, but it's very surprising. He must've had an enormous BC already full, and been a very efficient breather... a 48 lb lift BC holds 6 gallons, or roughly 24 L of air, or roughly 1 ft^3 when completely full. Considering a 3 L tidal volume and at least 10 breaths per minute, he's essentially breathed the entire BC after one minute. The second minute of breathing should put the oxygen content below 15%. Depending upon the depth, of course, there will be more oxygen available in the same volume.... but five minutes still seems Herculean. Can you tell me more about it?

The major broblem is that there is water in the inflator. If there is no air in your lungs you can't exhale to clear it. Attempt to inhale the water and you'll choke.

An extremely good point...

You may prefer death, but others might select a last ditch option.

But as I said before, you won't ever need to rebreathe the BC if you're shallower than ~100 fsw. If you're deeper than ~100 fsw, you should hopefully have reliable OOA plans established, and you again shouldn't need to rebreathe the BC. Therefore, rebreathing the BC is still the last of the last resorts, IMO.

- Warren

 

[Rick Murchison]

Originally posted by VTWarrenG
This is very surprising -- I don't doubt you, but it's very surprising. He must've had an enormous BC already full, and been a very efficient breather...

I don't think you understand the process, Warren. [I do not endorse rebreathing a BC, by the way] When breathing a BC, you use it like a counterlung - you don't exhale to the open sea, but back into the BC... The percentages of oxygen you're used to dealing with at the surface don't work the same way at depth, either. While exhaled air after a normal breath at the surface contains about 16% oxygen on average, at 100' it'll be nearly 20% after the first cycle & so forth, because we're dealing with consumption in the body based on metabolism [same number of molecules, not volume]. Same thing for CO2 increases - percentage wise they're less per breath than at the surface. [now the properties of pressure and CO2 buildup is a separate issue, and the news isn't at all good - but for rebreathing a BC for a few breaths the physics works to our advantage].
Bottom line - rebreathing a BC will get you a surprizing amount of breathable air at depth - but at great risk.
Rick

 

[solodiver]

Been there, Done that, had mild DCS as a result.
Bouyant emegency accent. from 70 ft. water temp 30 f buddys equipment failed, all octos failed, buddy paniced ripped my reg out of my mouth. we were only minutes into the dive, inflated my dry siut and took the elevator up. it's a long way up when you only start out with half a breath of air. If we had been down longer or deeper we probibly would have been hurt a lot worse.
I wouldn't want to try it from a 100 ft or deeper..

 

[JamesK]

Originally posted by solodiver
buddy paniced ripped my reg out of my mouth.

I understand your name a lot more now.


I have only tried it from 45ft. I have not practiced any deeper.

 

[VTWarrenG]

Rick,

Au contraire. I understand exactly how it works. I'll quote myself:

Depending upon the depth, of course, there will be more oxygen available in the same volume....

- Warren