Quote:
| Originally Posted by Mal Bridgeman I don't pop into this forum too frequently but I was reading the thread about the surface swimming thread and it has made me wonder what happens when you descend on a CCR....in say the first 10m.
Can anyone explain what happens in terms of maintaining the loop volume and the ppO2. Do you have to do this yourself or is it automatic?
TIA
Mal
P.S. You have to presume I know nothing of RBs
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Depends if you have an ADV (automaic dilutent valve) fitted or not. If you do then it acts baiscly the same as a reg, as soon as it feels negaive pressure against the diaghram it adds in gas. Basicly works the same as sucking on a reg(diaghram sucks in on inale and pushes needle valve and opens up the gas path in turn adding gas)
If no ADV you have to manualy add in the Dil via the counterlung buttons (when you feel negative pressure I.E cant suck in any gas-push the button on the inhale lung)
The use of an ADV basicly gives you one less thing to do, and leaves you hands free for the decent.
As for the PO2 on decent, it obviuosly goes up inline with the added ambeint pressure. But the addition of Dil keeps it within safe levels.
For whatt its worth i switch up to high setpoint (1.3pp02) @ 10m on decent even for deep 90m+ dives as the addition of Dil keeps my PO2 in the 1.00 region on the decent, it also allows me to spike the PO2 above setpoint on the decent to make sure cells are not current ltd (just hold my breath for a few meters and make sure cells reach 1.4-1.5).
So by the time i reach the wreck i am all set to go, and not have to faff about with switching from low to high and current ltd test.
ATB
Gareth