Another PONY Q!

[lowviz]

SeaRat,

I'm in no way challenging your extensive experience. My experience tells me that there is a period of shock/denial/acceptance when something goes terribly wrong.

I would not attempt a cold ESA from 130'. I would breathe anything until I got it all together and flushed
the adrenaline-driven CO2 out of me. I would then do your ascent with the reg in my mouth.

Our mileage varies.

 

[hroark2112]

If I were you, I'd qualify that by saying that I have had a chamber oxygen toxicity test, and I'm not prone to O2 toxicity so I would use the oxygen at a depth of 130 feet. Oh, you may not have had the chamber test; in that case, you're best off simply doing an emergency swimming ascent. You have enough air in your lungs and Scuba tank to take you all the way to the surface. And remember, we're in a "Basic Scuba" area, and are not doing overhead hazard diving or decompression diving.

SeaRat

Good thing you're not me.

Oxygen toxicity is a function of both PO2 level and time. If I have breathed out and am OOA, I'm taking a breath and heading up immediately.

As far as your comment saying I have enough air in my lungs...sure, in a perfect world, where I have not breathed out fully and knew I was OOA before I tried to take a breath. In your internet world, everyone can just do a CESA from 130' and be fine. In the real world, at 130', if you find yourself unexpectedly OOA, your first thought is not going to be "I'm fine, the instructor guy on the Internet says I have plenty of air!". My first thought it going to be "Either I'm going to drown or I'm taking a breath off this oxygen regulator and heading up!"

I know we're in the Basic Scuba area. I also know I was replying to the comment above mine, not telling brand new divers to grab a bottle of O2 and head to the bottom. At no time did I mention overhead diving or decompression diving. Thanks for your input though...I'll take it under advisement.

 

[BlueTrin]

Good thing you're not me.

Oxygen toxicity is a function of both PO2 level and time. If I have breathed out and am OOA, I'm taking a breath and heading up immediately.

As far as your comment saying I have enough air in my lungs...sure, in a perfect world, where I have not breathed out fully and knew I was OOA before I tried to take a breath. In your internet world, everyone can just do a CESA from 130' and be fine. In the real world, at 130', if you find yourself unexpectedly OOA, your first thought is not going to be "I'm fine, the instructor guy on the Internet says I have plenty of air!". My first thought it going to be "Either I'm going to drown or I'm taking a breath off this oxygen regulator and heading up!"

I know we're in the Basic Scuba area. I also know I was replying to the comment above mine, not telling brand new divers to grab a bottle of O2 and head to the bottom. At no time did I mention overhead diving or decompression diving. Thanks for your input though...I'll take it under advisement.

Actually that got me thinking: how much air does one have on his lungs when he has exhaled ?

The idea of CESA from depth is that air expands as you go up, that’s why you should be able to exhale a bit.

Also I think you can last a bit more if you can prevent the gag reflex and not inhale water.

I read as well that you’ll be able to usually take another breath from the reg mid CESA as the air in your cylinder will expand as well. If you inhale mid CESA the should you stop to avoid air expansion in your lungs ?

 

[hroark2112]

Anything is possible when you dive on ScubaBoard!!

 

[NAM001]

I'm using general use as a counterpoint to being filled specifically for the dive. Something that is kept filled and brought along to variety of conditions. You'd want an air mix that's safe in the widest range of potential dive profiles.

If, however, you knew that you were going to be diving somewhere with a 90' hard bottom, diving with the tank filled with say 36% could potentially help off gas nitrogen a little faster, especially if you have an emergency near NDL.

you cant have it both ways being specifically for the dive and brought along to variety of conditions. for the first I would do air or possibly the same >20% mix you are diving with. for the latter it would be air. since we are talking about rec diving it would be air. you will not take on much of any N2 in the emergency that calls on you to use the pony.

 

[markmud]

Pony is air. You don't decompress on a pony, you save your ass with one. Your pony is the very last horse out of Dodge.

You only get to put 3K psi in it so get a big HP tank full of air and a transfer whip. Keep your little pony topped off. Amazing how fast it drops just by charging and discharging after the dive...

Hi lowviz,

I think you gave the perfect answer on all points.

My pony is filled with air and sometimes topped-off with 32% if I have to whip-fill it and Nitrox is only available.

markm

 

[flyboy08]

Great responses, thank you all! Reminds me why I joined this site!

Happy New Year!

 

[Zef]

I read as well that you’ll be able to usually take another breath from the reg mid CESA as the air in your cylinder will expand as well.

The air in the tank does not expand...the ambient pressure decreases allowing the residual air in the tank to be delivered by the 1st and 2nd stage regulators at reduced depth.

-Z

 

[BlueTrin]

The air in the tank does not expand...the ambient pressure decreases allowing the residual air in the tank to be delivered by the 1st and 2nd stage regulators at reduced depth.

-Z

I understand: that’s what I meant even though I expressed it in a dubious way.

Technically the air in the tank cannot expand because the ambiant pressure is the same than the tank when you go up the ambiant pressure will be higher letting the air from the tank expand when you breathe in so even though it is a dubious way to express it, it is not totally incorrect. I get your point that the air in the tank does not expand magically by itself, but this was true CESA or no CESA.

 

[lowviz]

I think you gave the perfect answer on all points.

My pony is filled with air and sometimes topped-off with 32% if I have to whip-fill it and Nitrox is only available.

Thanks, but I have to pass your thanks on to @uncfnp who mentioned the nitrox top-offs first...