just a questions about deep dives

[dani_p]

Im am not implying that I am right and anyone else is wrong, but I have a question about deep diving. I have read a few posts of people that have been below 200 feet. Im wondering if this was done on air or heliox or what? I though someone had said they went that deep on air, and I have heard that oxygen toxisity can occur around 200 feet. Im not about to go out and try this myself, so please dont get the wrong impression, Im just curious. do they do a test for oxygen toxisity limits? how does it work?

 

[chickdiver]

Typically trimix (helium,oxygen,nitrogen mix) is used. These mixes typically contain alower percentage of oxygen than air.

 

[Kim]

You might want to look at this thread:

http://www.scubaboard.com/t53710.html

 

[Diver0001]

Im am not implying that I am right and anyone else is wrong, but I have a question about deep diving. I have read a few posts of people that have been below 200 feet. Im wondering if this was done on air or heliox or what? I though someone had said they went that deep on air, and I have heard that oxygen toxisity can occur around 200 feet. Im not about to go out and try this myself, so please dont get the wrong impression, Im just curious. do they do a test for oxygen toxisity limits? how does it work?

In your Nitrox class you'll learn about oxygen toxicity limits. The basic story is that O2 begins to become toxic at at a partial pressure of about 1.6 atomospheres.

Normal air at sea level (i.e. not under water) has a ppro2 of .21 (of course) because it has 21% oxygen content. Go to 10 metres/33 ft/2ata and it doubles to .42 and so on. So 1.6 is about 7.6 ata (1.6/.21) which would put you at about 66 metres or about 218 ft.

In your nitrox class they teach you not to go any deeper than 1.4 ppro2 to be safe which is about 58 metres/187ft on air.

That's how it works.

R..

 

[String]

Years ago people routinely dived >200ft on air. Yes a fair number died but a fair number survived as well. Today there are better methods (ie trimix) for very deep dives. O2 toxicity is one problem but impairment through narcosis is an issue before that.

As mentioned, O2 tox limits are now recommended at 1.4 for bottom exposure (revised down from 1.6 a while ago).

 

[IndigoBlue]

...I have a question about deep diving. I have read a few posts of people that have been below 200 feet. ...I though someone had said they went that deep on air, and I have heard that oxygen toxisity can occur around 200 feet. Im not about to go out and try this myself, so please dont get the wrong impression, Im just curious. do they do a test for oxygen toxisity limits? how does it work?

Ox tox can occur any time, but it normally does not occur on air until you exceed 185 ft [PO2 1.4 ATAs]. Beyond 185 ft, it is more likely to occur the deeper you go.

Years ago people routinely dived >200ft on air. Yes a fair number died ...

That pretty much says it all.

 

[DoUDive2]

As to "how it works," Chickdiver brings ups an interesting quandry regarding deep diving. By using a gas with less than 21% oxygen, it is possible to dive deeper without hitting the toxicity limit. On the other hand, when you are near the surface doing a safety or deco stop, the gas doesn't have as much oxygen as your body wants.

Chris

 

[H2Andy]

yup... hence they use several mixtures. some is good for depth, some for deeper
deco, some for shallower deco...

it's a whole new universe of complexity (and one which i am totally ignorant of, btw, i just read a lot)

 

[dani_p]

ah, ok I see. I wouldnt try going that deep anyways (Im a very novice diver) but I was curious. thanks for your responces. this stuff facinates me!


:newbie:

 

[dani_p]

You might want to look at this thread:

http://www.scubaboard.com/t53710.html

that was actually one of the threads that made me wonder about this!!!!!