AZ Nomad wrote:

They *can* be the same depending on the store. Welding grade isn't
safe for medical use.

Are you aware of any impurities that are present in the generation of
bulk O2 that are specifically removed when "medical" grade O2 is
created?

Stores often stock only medical grade instead of maintaining
multiple grades.

Even welding supply stores will stock only "medical grade" oxygen?

You people might want to read this:

http://www.avweb.com/news/pelican/182079-1.html