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gmirvine@sa*.ne* wrote:
>Wrolf, you have all the answers, right? You tell us what the right
>depth is for air - go ahead - tell us what is the depth for which air is
the correct mix using any set of standards >or logic you can think of.
>Let's hear it, Rolf, you can not hide behind anything else - thre is no
>bad language here, there is no attack - just you and you can now tell us
all the depth. What is the perfect depth for >this gas, and why?
I wanted to conduct a poll. It could prejudice the results to announce my
point
of view first.
However, my point of view is disappointingly conventional.
Bottom mix:
Depth/fsw Best Good Acceptable Marginal
0 - 60' Air. EAN 36, EAN32
60 ' to 100' EAN 36 Air, EAN 32
100' to 130' EAN 32 Air
130' to 180' Light trimix Custom Nitrox Air
180' to 200' Light trimix Air
200' plus Trimix
So air is the best mix from 0' to 60', good for 60' to 130', acceptable
from 130' to 180',
and marginal from 180' to 200'.
My principal assumptions are:
1. Max ppO2 < 1.5 ATA
2. Narcotic effects of N2 are effectively identical to 02
3. Narcotic effects of (any mixture of) nitrox are manageable up to 130',
and are
progressively less manageable until approximately 180' to 200', at
which point they
pose excessive risk for most dives.
So even if narcosis at 200' to 250' is manageable for a given diver,
profile, environment etc.,
CNS toxicity mandates adding helium to the mix.
But adding helium implies adding separate decompression gases to keep
decompression times acceptable.
Gas switches adds to task loading, so as soon as add any helium to the mix,
add enough to make the
END = approx 130'. For very complex dives, you can trade off more deco
time for less narcosis and set
END = 100'.
I would really like to know your opinion on this subject. When you refer
to deep air,
are you referring to the use of air deeper than 200'? 130'? 60'? On
grounds of CNS 02
toxicity, viscosity/work of breathing, narcosis, or what?
I would also like the opinion of the many other techdivers whose opinions I
respect.
Safe net.diving,
Wrolf
P.S. Gee, Irving! How *did* you know that I had all the answers? Fax me
$20 and I will send them
to you. ;-)
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