I cannot vouch for new practices, or other companies. However, back about 20 years ago, a very good friend of mine was a salesman for medical gases. He worked for a major gases company, and sold medical gases to hospitals, pharmaceutical companies,etc.
The company sold different 'grades' of gases. You could get plain old oxygen. You could get medical grade oxygen. The difference was in the labelled, certification and purity. He'd always laugh at that concept, since the company only made one grade of gas.... They did not make a low level welding oxygen, and a higher purity medical oxygen. They made ONE grade of oxygen, and it went in all bottles....
The cheap shit had a guaranteed purity level. The medical stuff had a higher guaranteed purity, lower guaranteed contaminants, etc. Thing was, it was ALL the higher, medical grade gas. Completely legal. When you bought the cheap shit, you got really good gas and at a great price. When you paid out the nose for medical gas, you got exactly what you paid for, really good gas. The company wasn't going to try to make shit grade gases. They made good stuff, stuck it into bottles, and sold it. Cheaper to make one grade and repackage than to try to make two or three grades...
No idea if this still holds true, or holds true with all companies. That was mid 90's. Interesting to note the margins on the medical stuff....
Fro