Breathing 100% O2 at depth...

From 99 feet the air in your lungs will expand four times the size. that's equivalent to 4 breaths (albeit reduced O2 each time). having done this, i can say that there is no urge to breath, but a very real urge to exhale. you won't even think of inhaling and do not need to go faster than 60ft/min and do not need the air in your BC (which you dump as fast as you dump your lung air/gas). and if you are diving with a buddy he will be there when you hit 15 feet and will lend you a reg for the safety or decompression stop. if not you can then switch regs and take a breath of the O2 you are carrying and figure out what to do from there.

if i had to breath o2 at depth or drown, i'd go for drowning. same for violating decompression. some have been revived after many minutes beyond the 8 they say is brain damage (with no ill effects), but few have managed to violate required deco without very painful death. I am assuming that deco obligation is signficant of course.

this is why when in open water I like to carry a 50/50 deco mix so that if I had a situation like this, I could do a rapid ascent but only to 70' so I could get on that gas, rather than shoot to 20 to get to my 100% bottle. Unfortunatly my computers don't like the deeper stops as much, but I think the gas exchange is better at that depth and helps me to complete a much safer deco schedule.

-Matt

100%O2 at depth=death
Run times to 1/3rd of your gas, or less, if some of your deco is on back gas. If you dont have the gas needed, you better have a buddy. Or a "buddy" bottle, so you will never need the O2. Life is to important to play the guessing game. Plan your dive, and dive your plan


My opion

Thanks all.

The posts were much appreciated. The question was posed as an open water question but as this forum is frequented by many well experienced divers I thought I would drop it in.

Regards.

kinetic

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Originally Posted by kinetic

what could/would happen if say, you had to take one or two breaths from a 100% stage bottle at depths below the recommended for 100%.

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If it was just one or two breaths probably nothing, see answer below from Dr Bill Hamilton to a similar question I asked him.

"A 3 second breath of O2 every 7 min or so will not be a toxicity threat. This would be true for up to 11 bar as long as the exposures are short.
Best to avoid this need, however. "

There are obviously very good reasons not to do this and it would have to be a VERY bad day out if you had to BUT when your life can depend on it you should have the best knowledge in order to decide what best to do.

Some amazing #### can happen sometimes that you would never imagine could all happen at once and despite the best of planning it is 'possible' that you may end up in the crazy sitiation that all you have access to breathe is 100% (anything is possible)

Basically 100% at depth does not (necessarily) equal death. Can it? Yes, but its not a certainty.

I breathed 100% whilst ascending at a controlled rate of around 20m/min from 72m up to 32m with no ill effects.

Why? Because I had no other choice!!! :-D

That's pretty much it.

If you have to, you have to. If you die, well, it was your day...... at least an O2 hit will likely leave you unaware of your demise, as opposed to some of the other alternatives....

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Originally Posted by Drmike

I breathed 100% whilst ascending at a controlled rate of around 20m/min from 72m up to 32m with no ill effects.

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I have (stupidly) run out of air at 14 m in a cave. Fortunately I had an (almost) direct acesnt to air. As I ascended I got another lungful out of my regulator as the amibient pressure reduced.

I have also (stupidly) breathed O2 in same cave at same depth. Had all the syptoms of an incipient tox - story on here somewhere. Not good. I witnessed another regular poster here get onto O2 too deep with the same symptoms I had. Being on a "hot" mix like having too high a ppN2 is a useful experience but not one I would deliberately seek.

However, when the doo doo is in the AC. Any gas is good to breathe. Call it "Plan Zed".