Scott, I have been dealing with issues like this with gas suppliers
for years. The purity issue is nonsense. The medical grade oxygen
is filled from the same bulk cryo storage as the industrial stuff.
The difference is that medical grade is periodically sampled and
analyzed for compliance with USP specs, which adds a cost overhead,
and on the medical grade, the filling procedure is slightly
different - vacuum is pulled, O2 is flushed at low pressure, vacuum
is pulled again and then the cylinder is filled. Industrial
cylinders either have one or no vacuum steps before filling. The
idea is to avoid any kind of hydrocarbon contamination, but such
risk is small. I have been using industrial helium and oxygen (run
through my own physical and chemical filters) for years without
issue. If you can do so, it will probably be cheaper. If not, just
explain your situation to your GP and you can probably get a
prescription. Another option to look for is so-called aviator's
oxygen, which is certified to have minimal moisture content
(prevents freeze-up issues), but may not track other impurities and
so may be cheaper than medical. For submarine breathing media,
industrial grade gas is fine provided you confirm the analysis (make
sure it's actually O2 in the tank at 99.5+ %). The breathable
atmosphere in your sub is exposed to external contaminants anyway
from your body, clothing, equipment and any dirt you may have
tracked in. Since you are conditioning the air anyway (via CO2
scrubbing), for peace of mind you could include other media stages
in your filter for scrubbing hydrocarbons, CO, etc. -Sean On 2012-05-06 07:53, swaters@waters-ks.com wrote:
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