BQ340 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 ?

Nope, they are the same. I see the paramedics at the welding supply
store all the time, getting their bottles filled from the same rack
mine are.

And just to be clear -

Welding oxygen is more (way more) than just compressed "air". And what
I mean by "air" is the stuff that's all around us right now.

Yes?