I looked up the same article you quoted for me and found on page 60 that "The lowest PO2 at which a CNS oxygen toxicity event was noted was at 1.3 atm. We explored the viability of using a maximum PO2 of 1.2 atm and 90 fsw as the maximum depth."
The criteria they were using at the DAN workshop was to only count recreational CNS hits, no tech hits, and no commercial hits. Brett Bjorkmann, from EnviroDive Services, wrote the text you are quoting. He is referring to commercial diving. Because it was a commercial dive, it wouldn't have made it to the count. The thinking behind this is that commercial and technical divers are often subjected to multilevel exposures, which "are a whole new ballgame."
That said the type of commercial diving he describes, fish farms, is shallow. So they are probably not being getting multilevel exposures, but they could be having more CO2 buildup because they stay down for long periods of time, potentially doing vigorous work all that time.
Page 94 says "There was one documented incidence of an O2 convulsion after 75 minutes at 25 feet...
Page 94 is part of the same conversation I quoted to you in page 95-96. It basically started with, something like, 'I know of this case and that case.' But when they got to the details of said cases, it turns out they were either tech dives with multi level exposures and an advil overdose. So they all ended up agreeing that there were no cases of single exposure at 1.6 atm or below.
Ok, after some searching, I found it... In the January/February Issue of Alert Diver, There is a 3 page article about an incident, suspected to be ox tox at 1.4ppo2. It was a tech cave dive.
DAN nitrox workshop said tech dives don't count. We also have to keep in mind that this is NOT scientific data, therefore it can hardly be considered scientific proof. Scientific data is obtained in controlled environments that try to eliminate other variables that could potentially influence the outcome. With this type of anecdotal "evidence" there is no control whatsoever over any variable. If somebody toxed at 1.4, there is no way of knowing if it was epileptic episode unrelated to diving. Conversely, because there is no control, diving incidents that could have included a CNS hit may have gone undetected and unreported. Also keep in mind that 1.6 is the upper limit. In a typical recreational scuba profile you will not spend a lot of time at the max ppO2 and not all of the dives will take it to the upper limit. So in reality maybe only a fraction of those quarter million dives actually went to 1.6 ppO2. Personally, I think 10 yrs and a quarter of a million dives is plenty chance to detect something while operating at typical parameters.
Here's another opinion:
Dan Kerem (2000) of the Israeli Navy Medical Institute, "I'll stress again that with pure oxygen diving, as long as your gear is okay and there is no CO2 buildup in the system, divers routinely dive for hours at 1.6 atm with no incidence of oxygen convulsion."
Just read slamfires post #27
best post read i have had in a long time.
I'm just regurgitating statements from people that are better informed than I am, and learning a couple of things in the process. I try to present different sides of the issue without bias and then present my own personal opinion. Thanks for the comment.