Ted,
Being a Paramedic, Pilot
and a Certified Welder, I have used all 3 types of oxygen extensively. Most of
the oxygen in the US is made in the liquid form because it
is much easier to store and transport. For the compressed
cylinders, they take the vapor off and compress
it. A friend of mine has a plant right next door to my office (scary). All
3 types come out of the same liquid tank. The difference is the
way the cylinders are filled. Medical oxygen
is required to put a vacuum on the cylinder and completely remove all contents
and then fill from a closed system meaning no air can get
into the tank after it is vacuumed
and before it is filled. This is regardless of whether or not the tank has been
emptied. Aviation oxygen has to be vacuumed if
the tank has been emptied. If it still has 200 psi, they can just
fill it. Welding oxygen does not matter.
The FDA regulates medical
oxygen and there has been some violations cited by
them for small ambulances that had their own cascade
system. The concern for medical oxygen is if the tank has been emptied and is not vacuumed,
then there can be nitrogen in the tank and when that get
compressed, something happens and the patient can get
100% nitrogen instead of oxygen. I would think it would mix with the oxygen but
it must not. I did hear of one death a few years ago, but do not remember where.
With aviation oxygen there is that concern as
well as moisture. Since airplanes often fly in freezing conditions
the moisture can freeze in the lines and cut off
the pilots oxygen. I see people using cascades to
fill both medical and aviation oxygen at airports all the time, but I am not sure
that it is legal. The oxygen place next
door says it is very dangerous to do if you do not have a vacuum
system.
Since the
oxygen comes from liquid, it is pretty much 100%
pure with no vapor. The only impurities are what is
induced in the filling of the bottles. This is a good case for
using liquid for both medical and
aviation which is becoming available more and more in both air ambulance and
ground ambulance.
Hope that helps!
-----Original Message-----
From:
flightmed-admin@flightweb.com [mailto:flightmed-admin@flightweb.com] On Behalf Of Ted Reesor
Sent: Wednesday, February 20, 2002
8:59 PM
To: RC World Professional Forum; flightmed
Subject: Differences in oxygen
suppliers
Greetings
all.
I was
presented with an interesting question related to oxygen supply and knew you
would be the people to approach. Given that there are four main types of
industrial oxygen markets out there; medical, aviation, welding and research,
what are the main differences in them other than cost. My understanding
is that welding oxygen can be of higher purity than the medical stuff and
aviation can be considerably cheaper. I went on a transport to the far
north once and found that the oxygen cylinders were labelled (I believe) 98%
USP versus what I thought was the 99.99% USP norm.
I realize
that legalities play an important part, but couldn't one argue that a higher
refined product meant for welding be as good or better than say, and oxygen
concentrator? I have found one article that has circulated in many many
web sites that briefly mentions it.
Ted Reesor, RRT/RRCP
Joseph Brant Memorial Hospital
Burlington, Ontario
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