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Hi all,

I've been lurking on this list for some time and find the discussions
lively and interesting.  I have already learned a lot.

I am a BSAC Dive Leader, almost Advanced Diver - just the theory paper
to go.  I have also recently completed the IANTD Advanced Nitrox Course
which was made easy from the discussions on this list and the Nitrox FAQ.
Most of my diving experience has been in UK waters with depths up to 50m.

Intro over, now to the point of the message!

Recent articles on the list keep referring to the acronym EAD to refer to
the air equivalent narcosis depth of a mixture.  This acronym is also
used for the Equivalent Air Depth required to calculate the decompression
penalty of a Nitrox mix from an air table.  Up until recently, for Nitrox
mixtures at least, these would have been the same depth.  However, I have
learnt over the last few days (Thanx Rich, John C et al) that O2 is also
narcotic, maybe even more so than N2.

Perhaps in the future we should use:

	EAD	for Equivalent Air Depth based on the inert gas PP for
		decompression penalty calculation, and
	END	for Equivalent Narcosis Depth based on the gases that
		contribute to narcosis, perhaps with multiplication
		factors in Rich's equation.
		(1.0 for N2, 1.0 - 2.0 for O2, ?.?? for Helium?).

Does anyone know how narcotic Helium is?

Safe Diving,    Ian   (I.Gould@bn*.co*.uk*)

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