pure o2...

[Mullins]

what I am certain of from the number of differing opinions is that noone really can say for sure if its safe or not.

Nope. Everybody is in agreement that using O2 in the 30-50ft range is suicidally dangerous. If you have a seizure, which is quite likely, then you're dead. Do some reading on Oxygen Toxicity - it'll be in the SCUBA diving literature rather than the freediving stuff.

Then there is pulmonary toxicity plus the less-studied but still fairly well demonstrated effects of CO2 narcosis, extreme hypercapnia and dulled breathing reflex.

There was a thread on using enriched air a little while back, that would be good to read. Something like EAN40 might be worth using, but only for very specialised tasks and in certain circumstances (like safety diving for slow or unpredictable divers).

 

[BennyB]

...only an moron would do it without having some science to back it up.

Believe it or not but these morons do exist, read forums and go do stuff on the basis that if it's on the internet, it's scientifically true.

 

[jay cluskey]

hi fishbound , even though you say your question was a recriational one fair enough.
all of the divers on here who are replying to your question are compitent competitive divers.
my advice is, if you want to play around with air ... take a padi enriched air course..if you want to learn about the physiology of freediving take a freediving course.
there are very few cross overs in the learnings of the two sports dont confuse them .
and as benny b says ... forums of all types are mostly opinions not knowledge although the replies on this thread are from knowledgable divers .
dive safe mate

 

[Mullins]

Just to be clear about where we're coming from - many of us have tried O2 in the pool, particularly for statics. The effects on breathhold time are as dramatic as you'd expect when you breathe air that's enriched by a factor of 5. Most people find that 10 minute statics become easy on oxygen. However none of us (I think) have been crazy enough to use O2 for doing breathholds below a couple of metres. Even when we decompress after deep CWT dives we do it at about 5-6m. This is because of the biggest risk mentioned above, which is CNS toxicity. Unpredictable, but definitely a good likelihood if you're operating around ppO2 of 2.0 for repeat dives. Causes a sudden seizure which is very likely to kill you.

 

[fishhound]

Thanks for all the posts and info. I have read them all and learned alot. I dive with very experienced divers(how I got into this),am going to read everthing I can get my hands on, and will take a course next year. With that said, taking a course ,as per alot of advice from posts, will not answer all of my questions relating to diving on pure o2 or a lesser mixture that may or may not be toxic since they don't teach that and since there have not been adequate studies done on this subject as it relates to our sport ie someone actually playing with o2 at different mixtures at different depths while under supervision from medical experts that could measure the effects on the body. That's what I was interested in and that's I asked. There are always new things that are fun to think about, some safe and some not. The techniques used today are quite different than what was used years ago and would most likely seem crazy to people back then. I don't do anything based on what I read from a forum(no disrespect to the knowledge on this site as there is obviously alot). It's simply another vehicle to gather opinion and information. I suspect there will be research done on this topic in the near future since people at the top of the sport are always looking for ways to push the envelope and I look forward to seeing those results...good or bad. Thanks again for all of the info.

 

[efattah]

I have done pure O2 freedives in the 0m to 7m range. There are several problems. First, you need to breathe aggressively for ages prior to the dive to gain any benefit in time. Second, around halfway through the dive I start to shake. My whole body starts to shake. I can stay down for a long time after the shaking starts but that can't be a good thing can it?

The last big drawback is that I accumulate so much CO2 that I need to take a 12-15 minute surface interval to blow off all the CO2 from the dive! What a waste of time -- and then I get cold and bored.

My recreational dive time in the 0-7m zone increased from around 3 minutes to around 6 minutes with the oxygen, but with the uncontrolled shaking underwater and the huge breathe up before, and the huge surface interval, combined with the unknown dangers -- not recommended so please do not try it....!

 

[Mullins]

Please note that whenever anybody says "nobody has been crazy enough to try this", Eric Fattah is always the tacit exception!

 

[Kars]

Thanks Eric, great insightfull post! - What about enriched air, do you have any experience with that?

 

[fishhound]

Thanks eric for some real life experience. Did the shakes come after a certain amount of time? You say halfway thru the dive...by what you said do you mean around 3 minutes? Was it better or worse depending on the depth? Have you done it for shorter periods of time and had better results by not pushing it? Doesn't sound like much fun at all with the huge surface interval...and also, how do you know you had such a large co2 buildup that required that much surface time? Have you played with a lesser o2 percentage? Thanks for the info and all very interesting.

 

[osusim]

Even when we decompress after deep CWT dives we do it at about 5-6m. This is because of the biggest risk mentioned above, which is CNS toxicity. Unpredictable, but definitely a good likelihood if you're operating around ppO2 of 2.0 for repeat dives. Causes a sudden seizure which is very likely to kill you.

Most of recreational and technical scuba diving systems as well as insurance companies accept maximum pO2 1.5 (pure O2 at 5m) or 1.6 (at 6m). Military uses pO2 in rebreathers up to 3 but who want to be expendable?