I have quoted the references for the last post so people do not have to seek them out.
The reference is to the significantly higher levels of PPO2 encountered in a chamber than are allowed by standards, and the two people responded by pointing out that toxing in a chamber does not lead to drowning. That is true, but there is another factor involved.
For reasons that are not well understood, people will tox in the water at considerably lower PPO2s than will occur in a chamber. IIRC, people can generally tolerate as much as twice the PPO2 level in a chamber than they can in the water.
On the other hand, I agree that the tolerances in the standards for PPO2 in scuba are very generous, and divers generally don't have to worry about a percent difference in their PPO2 measurement.
Exact oxygen % in Nitrox are nothing like as important and most of the nitrox course teaching leads candidates to believe. The values used are designed to give a very good margin of safety in recreational diving. HBOT treatment takes place using pure oxygen at up to 3 bar, in theory (as taught in nitrox class) that would be well over twice the pressure needed to kill someone, yet it does not.
If you OxTox in the chamber, which happens, you don’t drown. There is a BIG difference between high PPO2 in a chamber vs underwater.
The scenarios are quite different. OxTox doesn't kill you, anywhere. In the chamber the dive you carefully and bring you up if required. Spasm in the water and you'll drown. The margins are different because the consequences are different.
In reply to posts 217 & 218. What you say is reasonably accurate, but what I posted is true in regard to the context in which it was posted. Posters were implying that a small variation in % around the 32 % mark was critical which it is not. Ox Tox does not only cause the convulsions that usually result in drowning, there may be no convulsions but longer term damage can occur to other organs.
The reference is to the significantly higher levels of PPO2 encountered in a chamber than are allowed by standards, and the two people responded by pointing out that toxing in a chamber does not lead to drowning. That is true, but there is another factor involved.
For reasons that are not well understood, people will tox in the water at considerably lower PPO2s than will occur in a chamber. IIRC, people can generally tolerate as much as twice the PPO2 level in a chamber than they can in the water.
On the other hand, I agree that the tolerances in the standards for PPO2 in scuba are very generous, and divers generally don't have to worry about a percent difference in their PPO2 measurement.