Posted by Kendall Raine on November 01, 2000 at 11:30:10:
In Reply to: Maybe, all it boils down to is math. posted by Eins on November 01, 2000 at 09:42:05:
EAD is NOT what you read off your depth gauge. Depth is what you read off your depth gauge. EAD, or Equivalent Air Depth, "equates" the pressure implications of using EANx into air terms. That is, if you are using an oxygen enriched mix, the EAD is the air equivalent depth you would use to compute pressure for decompression purposes. Since with such an enriched mix there is less inert gas to cause a decompression obligation, I could use a shallower air schedule than actual depth to establish my no D or decompression profile.
All this assumes of course that the air table is correct, which it isn't. That's another thread.
You also mention narcosis in the context of EAD. EAD has nothing to do with the narcotic effect of EANx unless you assume oxygen is non-narcotic. Research and physical gas laws strongly suggest that oxygen is narcotic, however. END, Equivalent Narcotoic Depth computes the narcosis equivalent of the gas mix in air narcosis depth terms. For example, since helium is non-narcotic (HPNS is not the same thing as narcosis), a trimix dive to 250 fsw on 16% O2 and 50% He has the same narcotic impact as an air dive to 108 fsw.
Sorry to sound pedantic, but if you're going to sound off on the training value of nitrox for all forms of diving, you might as well get the concepts right.