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On Mon, 4 Jul 1994, A.APPLEYARD wrote: > On Fri 1 Jul 1994 09:54:28 +22305714 (HST) Richard Pyle wrote (Subject: Re: > O2 Rebreathers for hang):- > > > [The advantage of using an oxygen rebreather for decompressing, begins to > be lost if nitrogen etc outgassed by the diver accumulate in the rebeather's > closed circuit] ... > > How much bulk of nitrogen is absorbed by a diver?, even if he is (say) > saturated with nitrogen at 200 feet. Would it make much of an effective > concentration when outgassed and mixed with a breathing-bag-ful of oxygen? I've been trying to get a handle on this one for a long time. Bill Hamilton told me it was on the order of one liter per atmosphere at saturation. So, at saturation at 200 feet (say, about 7 ATA), there should be 7 liters of nitorgen (i.e., a LOT). Of course it all depends on how saturated you really are, and how big, err, um.... voluminous your body is. > > The solution, therefore is to periodically flush the breathing loop of the > rebreather. I haven't yet heard anyone put forth a recommended frequency of > flushing, though. > > Don't. Ordinary-sized small oxygen rebreather cylinders are soon emptied by > a few repeated flushings of bag + lungs. Flush once when going from air (from > aqualung, or at the start of an ordinary oxygen rebreather dive), then not > again unless you inadvertantly breathe air thereafter. When doing multiple-mixture closed-circuit deep decompression dives, I don't think you're gonna want to be using "ordinary" small diluent cylinders. The large-capacity diluent cylinders (e.g. 80 cf) also serve as open-circuit bail-out. > > an O2 rebreather would be an effective tool for decompression. It would > ALSO be a very useful tool for anyone attempting in-water recompression to > treat DCS. For this reason, I asked the rebreather manufacturers at the Key > West forum if they might be making inexpensive oxygen rebreathers for such > purposes. The general answer I felt I got was that the liability concerns > (apparently THE MAJOR road-block to rebreather availability) were GREATER for > the O2 rebreathers than for the mixed-gas ones (believe it or not). > Translation: "Don't expect them anytime soon". > > Where <do> ordinary people get oxygen rebreathers from nowadays?, if they > want/need one. I have no idea. For liability reasons, they're pretty-much only sold to the military. A Drager rep. told me that liability was too high for them to consider selling their O2 rebreathers to non-military, "ordinary people" Aloha, Rich
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