Some people do believe that. I was taught that when I was a UTD student. The vast majority still teach 1.4, and that is what I use.
---------- Post added May 25th, 2014 at 12:10 PM ----------
Very, very little about oxygen toxicity has been truly proven at the level usually accepted by the scientific community, and there is good reason for it.
A lot of the early work on oxygen toxicity was quite understandably done in recompression chambers. Then it was discovered that for reasons that no one I have ever heard of understands, oxygen toxicity while diving is very different from oxygen toxicity in the chamber. One big difference is that it occurs at much lower pressures in water than in the chamber. Thus, if you want to do a really good study of oxygen toxicity while diving, you would have to get a whole bunch of divers and subject them to oxygen levels at the edge of toxicity to see how they react. (That is essentially how PADI studied DCS for its tables.) How do you feel about participating in an experiment to see what it takes to put you into a seizure under water?
It is difficult even to use data from cases that occur in normal diving. For one reason, it is very rare, so you don't have a lot of data to begin with. Next, you can't really be sure that the person had oxygen toxicity. If they die without anyone seeing the incident, there is no indication that they did indeed have oxygen toxicity. All you see is that they drowned for some reason. If you want to see a good example of the problem, read the DAN report on Sudafed and oxygen toxicity. About half of the report is spent explaining the scientific method and why they have really no reliable data on which to draw a conclusion.
I was present for what may have been a very rare successful toxicity rescue. The diver was using a rebreather, and he signaled trouble, shut off the loop, spit out his mouthpiece, and reached for the regulator of his bailout bottle. His buddy donated his bailout regulator just as the diver went unconscious. Fortunately, his buddy was highly skilled and was able to hold his regulator in the diver's mouth while dragging him out of the cave propelled by a scooter, zipping by my group as he went. We were very pleasantly surprised to learn he had lived. Was it oxygen toxicity? The description of the incident sounds like a guy who had a warning sign of an approaching toxic event and wanted to get on a different gas supply. (Of course, it is hard to understand how switching to a bailout bottle with 52% nitrox at 96 feet is going to help, and I guess his buddy's 38% was better, but not much.) On the other hand, he did not have the supposedly characteristic seizure. It could have been something else. The hospital diagnosis was never released, since he lived and is in control of his own records under law. If it was indeed a toxicity issue, I suspect there would have been no sure way for the doctors to tell.
