Reply to:     RE>>Oxygen Decompression (c

Rich,


>High PO2 is not specifically what you're after on deco (although it may
>help in a variety of subtle ways).  What you're really after is low PP
>inert.  More to the point, what you're after is a gas mixture that has a
>low partial pressure of the gas that's dissolved in large quantities in
>your body.  People tend to think in terms of highPO2 = good deco gas
>because of the O2 per se, but this is just because O2 is regarded as a
>"freebie" gas from a decompression point of view.  I guess my point is
>that air at your deep decompression stops is just as good as an "ideal"
>nitrox, if you're coming off a very high helium-content dive (like
>heliox).

>Sorry for the nit-pick, but I just wanted to respond to the notion that 
>the PO2 must be high before a decompression gas will "do any good".

Thanks for the clarification. My point was the limited useful ness of taking an 
"air break" for the O2 clock using air vs. another mix at that depth (or near
it).

On of the other things I was questioning is that George uses a different
standard of "safe Narcosis" than you do, if I understand your gas switching
techniques. I believe that you once explained your techniques on TD and used
a transit mix (EAN 32) to 130, Bottom MIX for bottom, and O2 for Deco. Is this
still true 
and are  you still using the standard of PPN2 no higher than 4.0?

I would expect that George would opt for a mix other than AIR at 190 as 
this might pose an unacceptably high PPN2 in an overhead situation. Given
the number of gasses used by WKPP and the labeling method, I would expect
that the rational that AIR is easier and will live with the narcosis is not in
George's
character.... do it right or not at all.  My opinion is that an optimal mix is
a better 
way to dive this situation (enough helium to lessen the PPN2). 

George???

Steve

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