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>I just got done reading the long rebreather info (commercial? 8-) that was
>posted recently. It specifically mentions that the Odyssey works around the
>single point of failure I mentioned in the Draeger unit by making the bag
>demand fed and flushing 20% (or so) of the exhailed air for each breath.
>But it doesn't say anything about how this flushing is done. Does anyone
>know the mechanics behind this device? Can you explain how it works?
>
>Seems to me you've just substituted one single point of failure for another.
>If this valve they have doesn't work to it's full 20% it won't be getting
>out the right amount of bad air and, therefore, you won't get as much good
>air. I guess it depends on whether you trust the Draeger (and others) feed
>system or the Odyssey exhaust system more. Comments?
>
>Devon

I'm not familiar with the Odyssey, but "The Physiology and Medicine of
Diving" by Bennet and Elliot describe a French rebreather that expells a
portion of the breathing gas with every breath. This system uses a large
bellows with a smaller bellows located inside it. When the large bellow
expands (diver exhales) the smaller bellow also expands creating a vacuum
that pulls gas in through a one way valve. When the large bellows contract
(diver inhales) the smaller bellow forces the gas that is trapped inside it
out through a one way valve and into the water.

However, it is my understanding that the Odyssey is more complicated. The
amount of gas exhaled  is also determined by the depth.

                              WATER
                              Valve
                ---------------^^^^---------------
                <           <       >             >
                >           >       < Small       <
 Large Bellows  <           <       > Bellows     >
        -->     >           >       <  <---       <
                <           <       >             >
                ---^^^^-------^^^^^------vvvv-----
                [ Valve       Valve      Valve    ]
                [  Gas   In         ]  Gas out    ]

OK, so I'm not an artist. I would like to read more about the Odyssey,
especially the accident if one did occur.


Mark Pansing  NSS 26348
markp@co*.co*

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