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I have some questions regarding rebreather design myself. After reading the below, I started wondering about breathing bag design. How do you make sure that you can always suck the gas out of the bag, especially in the example below where the exhaust is on the bottom of the bag/BCD (could not the vinyl collapse around the exhaust port sealing or at least making the flow of gas difficult)? I do notice a good bit of air relocation with my BC on the bottom when I switch positions. So top wouldn't always be the top if I'm upside down? Is a semi rigid breathing bag the design of choice, i.e. bellows? Bill and Mr. Appleyard, could you please send me your addresses privately so I can swap information with you more efficiently? Thanks--DD David B. Drake EDS/SATURN Infrastructure 8-320-4190 on GMnet Spring Hill, TN USA Internet: saturn.ddrake05@gm*.co* P.S. How do you get rid of the inert gas buildup in a completely closed rebreather system when doing IWR. I assume the amount of Nitrogen/He that will come out of your body will be more than significant to the size of your counter lungs and reduce off-gassing efficiency... Richard, are you still out there, can you respond to this? _________________________Reply Separator___________________________ >Dear Mr. Appleyard (1) The A.P. Valves bcd seems to rinse easily between the cloth outer material and the inner vinyl bag. I have used these bcds for years and have accessed the inner bladder directly, it was always clean. (2) I envisage the cannister being mounted in the existing tank strap. The hose routing would be; cleansed gas exiting top of canister running to right port of a full face mask, exhaust gas would exit mask via left port to enter bcd at orifice originally intended to mount the low pressure inflator hose assembly. The exhaust gas would exit the bag at what was the original site of the over pressure dump on the lower left rear of the bcd, the co2 rich gas would then be routed to the bottom of the scrubber stack. As o2 was metabolized it would be made up as required from the already plumbed bail out bottle. I have not considered using a larger inflation cylinder yet. For my planned application if the bottle was filled to 2400psi I expect the gas to last 2 to 3 hours (depending on degree of activity and amount of system puging) If you have access to a decompression program that allows surface O2 you will quickly see that prebreathing times on the order of 20 to 40 minutes yield the greatest benefit with reducing decos for most dive profiles. Used free swimming with moderate exertion the unit would give some what less that 1 hour which would be appropriate from the perspective of cns toxicity. If on the other hand you wished accomplish an in water o2 recompression and needed extra gas duration, A.P. makes a low pressure inflator feed that is intended to go inline on their corrugated breathing hose. Plumbing this in would be an easy and unobtrusive way of accessing gas supplies other than the built in bail out bottle. Best of the Season! Bill
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