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> pyle, on the solenoid sticking open thing.how much pure O2 at 300' is it > ok to have pumped in the breathing loop before its a problem?even if its > only open for 30 seconds before you notice it and get it properly shut > down,is that too much pure o2? - jt Clearly what we have here is a failure to communicate. A normal solenoid injection, at least on the rebreather I use, doesn't last very long - maybe one second maximum. That means if a solenoid is stuck open, I'll know about it maybe 2 or 3 seconds after it sticks open - not 30 seconds after it sticks open. Lets say my hands are occupied, say, catching in infamous counterlung-eating reef fish. Uh oh - prescious seconds are going by while the O2 is injected in the loop. I know that I have at least one, maybe two full breaths of safe PO2 gas to breathe before the high PO2 makes its way around, so I'm not worried. I take a breath, put the counterlung-eating reef fish in my catch bucket, then shut down the solenoid supply valave (1/4 turn valve). Oh, shit! The valve is jammed! A little knob fell off of Kevin's video camera housing and wedged itself in the valve - I can't turn it! And to make matters worse - I've been holding my breath almost 15 seconds already. What to do? What to do?! Wait - I know - flip the OC bailout switch on my mouthpiece! That's it! Now, you say I'm at 300 feet? O.K., that means I must be on heliox as my diluent. When full, it contains 30cf. But I've used 100psi already, so I'm down to only 29 cubic feet. Golly, that's only gonna last me - what - 10 minutes? Time's ticking away! After giving Kev the technical diver's "Are you O.K." sign, I try to get that little knob out from the solenoid cut-off valve. But it's stuck for good. Shoot, and look what else - my O2 supply is almost gone because it just flushed my whole loop. No worries, because I have my secondary O2 supply, still totally full. Ohmygod! I'm down to 2500psi in my heliox tank! Only 8 minutes left!! Better get back on CC. But of course, with pure O2 in the loop, I probably would only last about 5 or 10 minutes breathing from it. No problem - just flush the loop with heliox. Down to 1500psi now! But now the loop has heliox in it, so I switch back to CC. But the PO2 is now down to 1.0 atm, because my heliox supply is 10% O2. Better bring that back up! A manual blast or two from my secondary O2 supply does the trick just fine. Time to go back to the surface - since I only have half my O2 left, I've only got 8 hours of dive time left. Oh, but wait - my scrubber is only good for another 6 hours, so I guess I have only 6 hours left. On the deco, I need to manually add a tiny bit of oxygen to the loop every five minutes or so. What a pain! When I finally get back to the surface, I'm bummin' because I wasted a full 15cf of heliox. Now I have to fill that cylinder again before the next dive. I also have to get that friggin' knob out from the solenoid cut-off valve. I can't find a screwdriver, so I take the dome port from Kevin's camera housing and start pounding with it until the knob pops out.... Rich
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