Posted by Steve on July 21, 2001 at 00:00:59:
MHK wrote:
"NOAA recommends 45 minutes at 1.6.. George and JJ do 8 hours without incident. That is because you blindly follow what other's tell you and don't do any research for yourself."
Mike, I don't blindly follow others believe me. While George is out here could you confirm your statement above. I don't believe they would survive 8 hours at 1.6 PPO2 as you claim. IMO, they would be deader than a door nail. I had a discussion with Dan Volker about nitrox and high PPO2. You and Dan are at opposite ends of the spectrum on this issue.
Dan Volker wrote:
What I really had in mind related more to 100 to 120 foot deep diving, where I see Nitrox badly misued. I see the real problem is with Nitrogen, and adding oxygen to the entire dive has been the cheap fix for all depths up to 150 feet deep or so. I like Oxygen for creating a large gradient to remove nitrogen, but I like to keep my exposure to high levels of O2 to shorter durations. While I don't have definitive scientific studies "I" can cite on this right now, my concern is that high PO2 is harmful, and while short durations are
easily handled by your body ( repair), purposely diving hot nitrox mixes for 3 to 6 dives in a day will be very unhealthy. I expect it to cause much more prevalence of random oxidative metabolism,
which will create very high levels of free radicals....,it is bad for many enzyme reactions, and as we all know, when oxygen is inspired for way too long at a given depth--even 70 feet, your enzyme systems will shut down, and you will tox. Everyone likes to ignore the middle part---where you are not shutting down, but clearly, your system is adversely effected. Bottom line, if I go tech diving I will need to use 50/50 for deco from 70 feet on up to the surface, but only for the duration of the deco, which will generally be less than 40 minutes. For the dive previous to the deco, my PO2 will rarely be much over 1.2 or 1.3, and the goal is to keep it as close to 1.0 as is feasible, particularly for any significant duration. In tech diving, we "do" expose our bodies to risks and effects unacceptable to
recreational diving standards ( or what they should be). Gas choices, smart profiles, and extreme fitness levels will help minimize the damage ( and it appears that "small damage" will be repaired by the highly fit diver).