>All of your PP02s are about 1.6 except for 190 feet (1.41). Do you consider
the 
>190 depth a working depth and/or is this a close PPO2 to your bottom gas? Why 
>was 1.4 chosen versus 1.6 for 190 ft?

Steve Hogan

       The 190 is only if there is vertical relief, as we usually dive a 130 
AED, but in deco, we have trimix on our back, so can switch to that if there is 
some prpblem to deal with. We do not need 1.6 ppo2 after we have been diving a 
steady 1.4, we need some relief, but we need to begin deco,and the back gas at 
that point would not deliver oxygen in a high enough partial pressure to do as 
much good as air or a different trimix. We also carry this air with us through 
other stops. For a lojnger deco, we would put in a trimix at the deep stops
just 
for that purpose, for instance if we were on a 320 profile and wanted to do
some 
time at 260 - 200.

        The 1.6 is our MAXIMUM deco PPO2, so is only evident for the first stop 
of a gas switch. To use air to deliver 1.6 would imply an unacceptable
narcossis 
risk and slam risk in a cave as well. It is unnecessary. These are the shortest 
stops. Running high narcossis is not ever a good idea, and the damage the high 
PPN2 without helium does is ridiculous. - G

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