Posted by Eins on October 28, 2000 at 22:46:28:
In Reply to: RE (from Eins): Ken, are you sure you know what you're saying? posted by Ken Kurtis on October 28, 2000 at 21:33:06:
Ken,
It is my fault that I quoted this specific statement of yours. This in turn made you think it needed more explanation. It was not necessary, I know very well what you were saying (and I often make the same point, if in other contexts).
My concern was that you appeared to deny the added safety margin of a dive to only 75 fsw (25% safety margin) or 81fsw (19% safety margin) vs. a dive to 100fsw. All under the assumption that the deeper the dive, the greater the risk of an unexpected hit and assuming all dives are done within NDL).
But then you agree after all (but may not be aware of it). You said
"Ironically, there's a very easy way to get ALL the presumed "safety" benefits of nitrox without taking a class, without buying an extra gear, with using nitrox. All you have to do is dive shallower &/or dive shorter. My air dive to 75 is the same (based on your statement and numbers) as your nitrox dive to 100. Should be the same relative risk, n'est pa?"
Exactly. Dive shallower or dive shorter.
With EAN36 to 100 fsw, I'm diving shallower: I'm diving 75fsw. If my target (the Yukon) lies at 100 and I have no choice but to dive that deep, I am actually following your advice and am subjecting myself only to the risk level of a 75fsw dive but still reach my target.
It is now up to me whether I want to play it safe and gain 25% safety over an air diver but give up longer bottom time or whether I want to exploit the longer bottom time and give up my extra safety margin or I even have the option of a combination of both. That is the beauty of Nitrox. N'est-ce pas?
Your probability statistics are quite unprecise. If you go one step further and accept that of the assumed 20 million dives, a large number x is done within low-risk parameters, and if you accept that this large number is therefore very unlikely to produce many accidents, you will come to the conclusion that the ~1000 bends cases are concentrated in the smaller number of higher risk dives. Now your probability to get hit is significantly higher.
Nobody is proposing to use Nitrox on each and every dive. What some are proposing (and that makes a lot of sense) is to use Nitrox on dives that are within the EAN limits but beyond the shallow ranges where the risk is not so high. I would say the Yukon is such a dive where Nitrox makes a hell of a lot of sense. Either to extend bottom time for the unafraid or less at risk (because younger), or to increase safety for the concerned (or more at risk, because our age group).
You enjoy your diving. I have to work.
Eins