"Some Guy" wrote in message ...
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 ?

Certification. Medical oxygen has to be certified to a certain purity,
welding does not. You pay for that test and the potential liability that
goes along with it.