daniel f aleman:
Who is this "we" Andy?
I do not IN FACT know whether I am diving "safer" on EANx than that of air, I dove a gazillion dives on air to depths below 100' over twenty years - I'm still here.
Now, as I've said, I stopped diving on air seven years ago completely (after Trimix 2)... so...
Dan,
This "we" is people like myself, and many others who teach instructors how to teach this stuff.
Certain things about Nitrox rise to the level of facts. First, we are merely changing the ratio of Mother Nature's Nitrox (i.e. air). Thanks to Dr. Morgan Wells and Dick Rutkowski of NOAA, two mixes of Nitrox were standardized, and named NOAA NITROX I and II (NNI and NNII). These are, respectively, 32% and 36% oxygen, with 68% and 64% nitrogen.
Logic demands that, if we dive air to a given depth for a given time, we take on a certain amount of nitrogen in solution (us) based on the physics of the problem (i.e. Henry's Law). If we then dive NNI or NNII to the same depth for the same time, we take on less nitrogen. Things are simple, up to this point.
Then we get to the problems of levels of increased oxygen, and also to statistics. Suffice it to say that standarization has determined that, for reasons of safety, we do not wish to go above a partial pressure of 1.6 for O2. That limits our depth to 110 fsw for NNII and 130 fsw for NNI (don't begin the hair-splitting yet). Air, of course, does not reach that point until 218 fsw.
Conveniently, the depth limits just named for our Nitrox mixes are right within the recreational diving limits. Simple, yes? Simple, no!!:06:
We have to decide which we want; an increased margin of safety, or the same safety margins (as on air), but with more bottom time. Statistically, there is only a minor increase in the safety margin when diving nitrox on air tables. It is there, but it is minor. Most folks opt for the "more bottom time" option.
There are, of course, lots of anecdotal reports from the field, that diving on Nitrox mixes just makes one feel better at the end of a diving day, compared to air diving. Now, I had one famous researcher, whose name you would know well were it mentioned, who told me that anecdotal reports are not regarded highly by researchers. One, because they come from un-trained observers, but mostly because, two, the researcher doesn't get to have his name on the study and doesn't get paid for it!
So, while this is the quick and dirty, it really does boil down to personal choice as to the way you, as a diver, utilize Nitrox. The "Voodoo Gas" has really come into its own!:luxhello: