More on Nitrox Safety - Toxing @1.4 - Myth or Fact?

[ianr33]

From another thread on Nitrox:

I may be missing it, though. Can someone give us documented facts and numbers of divers proven (not talking internet speculation) to having suffered oxygen toxicity at 1.6 or less? How many this month? This year? In the last five years?

Is it even possible to prove an incident was caused by oxygen toxicity? Especially if the diver is dead.

I would imagine that proof would often be very difficult/impossible.

 

[Rhone Man]

What little I do know about Oxygen toxicity is that that CNS clock is calculated by multiplying pp02 out over time.

It follows from that logically that you could black out breathing oxygen at (say) 1.2 ATA, if you only did it for long enough?

If that is right, then you know what they say about 10,000 monkeys and 10,000 years....

 

[String]

O2 tox has 2 different manifestations - CNS and whole body.

Whole body is not an issue on open circuit diving, is i believe only a theoretical risk on extreme rebreather dives and results mainly in reduced lung function.

CNS% is the issue for diving. There is the "clock" as mentioned. Related to exposure time and partial pressure of which an average human can stomach x%. There is also the risk of an immediate acute seizure as you move to the more extreme ends of that scale.

 

[Thalassamania]

I don't think that either of those cases are creditable 1.4 tox cases.

 

[Rick Murchison]

I don't think that either of those cases are creditable 1.4 tox cases.

I agree with that assessment.
Rick

 

[lamont]

Is it even possible to prove an incident was caused by oxygen toxicity? Especially if the diver is dead.

I would imagine that proof would often be very difficult/impossible.

That's the problem that I have with the reports of divers at a ppO2 of 1.4 or less who suffer convulsions and drown. There's no way of knowing if it was the O2 or if it was just a seizure disorder presenting itself at an inopportune moment. Given enough divers and enough time you'll have some frequency of convulsions and death occuring underwater even without increased ppO2s.