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Oxygen Toxicity

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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New Member
Aug 9, 2002
Now, we've learned that freedivers are subject to Nitrogen Narcosis. If freedivers have that much volume in the lungs could they, then take a CNS hit? We all know that early experiments have conclusively proven that regular breathing air is deadly when breathed at a depth of over 300 feet, some folks more succeptible than others...

Have there been any experiments or injuries related to Oxygen Toxicity? Is this a real threat for the deep folks?
Different problem.

oxygen toxicity is not instantanous. Since freediver do not stay down very long, i dont think it's a real threat. On top of that, while going down to reach the 300 feet, you consume O2 so the partial pressure of O2 lower as the ppm (part per million) lower. So at 300 feet a diver would have say 15% O2 ( 20 % at surface minus the 5 % consume while going down) he would then be able to keep going down.
A real threat

O2 toxicity while freediving is a real danger when diving over 90m, especially in variable ballast and no-limits. Pipin Ferraras, Audrey Mestre and Stefano Makula have all blacked out at 100m+ from O2 toxicity. In the case of Pipin and Audrey, they were on their way back up on the sled, so they 'woke up' again in the shallow depths before surfacing. Stefano was not so lucky, and he had to be dragged back to the surface by the scuba divers. It is also possible that Cyril Isoardi died from an O2 blackout at 130m on the last dive of his life when he failed to re-ascend (with no safety divers).

Despite O2 consumption, these divers are way beyond the O2 toxicity depth.

Eric Fattah
BC, Canada
variable and no limit

So, the problem only occurs with variable and no-limit since they go down faster and deeper and they dont consume as much O2. Eric, do you think we should use another method to prevent oxygen toxicity or will we have to live with that?
From a commercial diving standpoint...@ 500 FSW, the mix for a diver would be 8 to 10% O2, so the necessary mix would be 90/10 or 92/8. Slim pickins ain't it?
The solution to the problem is to dive with less air in the lungs, which obviously has a Catch-22. We need to find a way to use oxygen more efficiently or transport it more efficiently, like whales and seals.....many dive with no air, avoiding toxicity and DCS.
Erik Y.
Shutdown limit

at what level of O2 does the brain shutdown. Can you train your brain to keep going at lower O2? Is the brain shutting down at a certain O2 % or at a certain molecule by ml of blood?