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>>1. Is there more than one solenoid in a single breather? > >Yes there are two on the CCR500: one for the O2 tank and one for the >diluent (air or the crazy gas of your choice ;-) They've probably done this to prevent ox tox on descent. Is there demand addition and if there is which gas is added by the demand valve, oxygen or diluent. >> 2. Why can it only fail open? > >No, it can only fail *closed*. The no current poistion is closed. Oops! That's what I ment! Anyway I wonder if this is true. That because of the nocurrent position being closed it can't fail open. There is an urban legend that these things can fail open. However I do not have an incident report of this happening. >> On a slightly different subject we took 1 measurement of swimming VO2max >> on our semiclosed circuit constant mass flow rebreather at 2 ata. Result >> was 2 lpm. > >How did you calculate that? i.e., what was the EANx, the mass flow and the >PO2 change? The mix was 47.5% O2 the flow rate was 8.15 lpm. We have plumbed a submersible O2 meter into the loop. Bill then descended to 2 ATAs and swam like mad for about 5 minutes while I followed directly above. Loop FO2 dropped to ~32% during the swim ( PO2 = .64 ATA ). We calibrated the PO2 sensor before the dive then checked it after and there was no drift in the calibration. The flow rate was checked hyperbaricaly before the dive. We then used the counter lung equation to work out VO2 ~ 2.00 lpm. I took photographs of the dive and hopefully will add some shots to our entry on the IANTD Canada page and Erics rebreather page next week. The other interesting observation was that when you are at rest or just poking around the inspired FO2 is almost the supply FO2. For example we mucked about at 10 fsw for about ten minutes after the dive. The FO2 was about 45%. From a physiological perspective you really are getting the benifits of Nitrox. Barrie
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