The other possibility is that your lungs are larger than the counterlung. The counterlung, not intended for underwater use, is very small. If you are a marathon runner and generally a large guy, you may be overbreathing the counterlung, and you will find that it will vent pretty much continuously. Yes, this is annoying. The other factor of course, is that at that shallow a depth, it will vent a lot with very little change in depth, it happens much less as you get deeper. Personally, my lung volume is only a tiny bit smaller than the counterlung, so I get venting at almost every depth change, usually as little as about 5 feet. This is annoying, and wastes gas, but that is what you get with a nearly free rebreather. There is a way around it, by building a larger counterlung spacer, but it takes some mold and machining experience. Sorry on the outrageous delay. jason
Mike- I'm not sure what happened, or if I actually responded, but your message did not go to my inbox- it is in some rebreatherworld backwater. Anyway, let me quickly respond, and if you are still working on this, perhaps this info will help. Two things are happening with the venting. First, there is a possibility that you have the IP set too high, and there is too much O2 going into the loop. This can only be confirmed by watching your O2 display, and if it continually creeps up, this is the cause. Of course, your O2 consumption will change between hanging out in 10 feet of water and swimming, so depending on how you want it set, this might be alright with you. Personally, I like my o2 to be at my resting level of usage, so it doesn't creep on deco, and then I let it drop while I swim, and just add as I need it. I prefer it lower than higher.
I saw your message to rchrds. just get rid if the OPV..We did see http://www.airheadsscuba.com/bletsop2.html We use an OPV from a lift bag, just to prevent bag from rupture in the event we forget to turn off the O2. Dale