Rebreather World - View Single Post - Diluent selection and the great alpinist v siege debate

Sutty · 1st January 2007, 16:03

Thanks for the valve info Dave/Dutchy.

To get back on topic again..

I can see the benefit of rich-ish dil in terms of SCR mode deco benefit, and in the avoidance of hypoxic incidents near the surface (though you can drop a fair bit below 0.2 without problems - think what your PO2 is at altitude eg skiing at 3500m).
I can also see that in most circumstances having your PO2 at 1.6-1.8 for a couple of minutes while you drop the PO2 by metabolism is unlikely to cause problems.
However I can see the benefit in having a mix lean enough to lower PO2 quickly if you think you are at risk of imminent CNS O2 toxicity (susceptibility does vary from person to person and day to day). This makes me wonder whether it would be feasible to have a very small cylinder (eg as used for SMB inflation or on Buddy BCDs) filled with lean gas, as an emergency PO2-dropping feed to the loop, while having a fairly rich dil for normal use.

Neil

1st January 2007, 16:03	#50 (permalink)
Sutty Classic Kiss diver Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Jun 2005 Location: Glossop, Derbyshire, UK Posts: 834	Re: Diluent selection and the great alpinist v siege debate Thanks for the valve info Dave/Dutchy. To get back on topic again.. I can see the benefit of rich-ish dil in terms of SCR mode deco benefit, and in the avoidance of hypoxic incidents near the surface (though you can drop a fair bit below 0.2 without problems - think what your PO2 is at altitude eg skiing at 3500m). I can also see that in most circumstances having your PO2 at 1.6-1.8 for a couple of minutes while you drop the PO2 by metabolism is unlikely to cause problems. However I can see the benefit in having a mix lean enough to lower PO2 quickly if you think you are at risk of imminent CNS O2 toxicity (susceptibility does vary from person to person and day to day). This makes me wonder whether it would be feasible to have a very small cylinder (eg as used for SMB inflation or on Buddy BCDs) filled with lean gas, as an emergency PO2-dropping feed to the loop, while having a fairly rich dil for normal use. Neil __________________ Never forget that life is a finite resource.
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