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On Sun, 3 Nov 1996, Richard Pyle wrote:
> The reason I describe this "trick" is to nail home my point about PCO2.
> If you start with a certain PCO2 in a rebreather loop at a depth of 200
> feet (say), and then start to ascend, the gas in the loop will expand and
> vent out of the over-pressure relief valve (or nose, or wherever). Some
> of the molecules in this vented gas will be CO2. This means that the "n"
> of CO2 molecules in the loop drops (net loss of CO2 molecules), and it also
> means (as detailed above) that the PCO2 drops.
>
> Now let's take the reverse. Suppose a diver starts at 20 feet with a
> certain PCO2 in the loop, and then descends to 200 feet. The volume of the
> loop is held constant by the addition of diluent and O2. Unless there is
> an appreciable amount of CO2 in the diluent or O2 supply cylinders, then
> the PCO2 will NOT increase on the descent, because the "n" will not
> increase (where would the addition of CO2 molecules come from?). Ya with me?
>
Rich,
Correct me if I'm wrong, but this is the same principle that
allows you to dive with a constant ppN2, right?
My question is a tangent, but once you ascend you lose most of
those N2 molecles,right. So is your decompression mostly heliox and how
does that affect your deco profile, if at all?
Also, do you lose most of the N2 on dives where you have to go up
and down(just 20" or 30') or do you avoid that kind of profile?
Aloha
Tony
ANTHONY MONTGOMERY
Marine Option Program Waikiki Aquarium
1000 Pope Road MSB #203 2777 Kalakaua Ave
Honolulu, Hawaii 96822 Honolulu, Hawaii 96815
Fax: (808) 956-2417 Fax: (808) 923-1771
Phone: (808) 956-6000 Phone: (808) 923-9741
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