Many have commented so far. let me add my 2 cents.
The O2 in a welding tank is the same as the O2 in a medical bottle. That is an established industry standard.
HOWEVER...
Medical O2 bottles are certified CLEAN, industrial bottles are NOT.
I teach at the Divers Institute of Technology in Seattle. A commercial diver training school.
We would NEVER use welding oxygen on a decompression chamber. We have 2 active chambers on campus. We use what are called APO bottles ( Aviator Provider Oxygen ) They look just like a large industrial oxygen cylinder, but are green instead of blue and are are clearly marked on the tank label as breathing oxygen. If an APO bottle is ever used for a cutting torch it can NEVER be used for medical oxygen again. That happened on campus last year. We had a cutting torch rigged up on the welding barge. I looked up at the peer and saw a green bottle hooked up to my torch and shut the whole operation down. We had to call Central welding immediately and have them haul away the tank to be decertified for medical use and restamped at the fill plant.
No joke.
I have used my cutting torch oxygen in the past to get over temporary breathing difficulties from excessive aluminum oxide dust, but I never breathed only the bottle oxygen. I fed it into my cupped hand to mix with air. Still makes me nervous not knowing who might have contaminated that bottle in the past.
Acetylene is lethal to lung tissue.