On Friday, June 18, 2010 at 8:58:42 PM UTC-5, Some Guy wrote:
Is there any difference between a tank of welding oxygen vs medical
oxygen as far as purity, concentration, hazardous impurities, etc, that
would render welding oxygen insufficient (or even dangerous) for helping
to supplement breathing / respiration ?

In my area of the mid-continent fly-over country the commercial fill plants that fill "welding" oxygen cylinders also fill FROM THE SAME BULK STORAGE tank (whose contents are generated by their in-house oxygen separation plant) MEDICAL oxygen. There is no difference as to purity. It's all essentially laboratory-quality (I use 'gas' in a lab setting; the same truck that delivers our welding oxy also delivers to the lab) oxygen. There may be a difference in aviation oxygen due to moisture content that might freeze at altitude. My knowledge of engineering would indicate that the oxygen separation process would by virtue of its temperatures also remover ALL moisture. If there is a separate FAA criteria, I suspect it's somewhat artificial as to whose turf is being invaded---similar to aircraft A&P mechanics required to have different licenses simply to change oil in an airplane.