Q: Is it true that medical and welder’s oxygen differ from aviation oxygen?
A: There are no different grades of oxygen being produced or contained in cylinders under DOT regulations.
Contrary to common myth, medical oxygen contained in a medical cylinder is no different than that contained in a cylinder marked aviators oxygen or otherwise. Furthermore, because of the chemical nature of oxygen it must be as pure and dry from water as possible if stored under pressure. Oxygen is produced to be better than 99.9% pure, if not damage or contamination will result to equipment. Oxygen even holding the slightest amount of water moisture–which is added during delivery for medical and industrial purposes–may have helped to cause confusion in the industry. As far as the FDA is concerned, any oxygen cylinder marked as USP or medical is a drug, and has to be held, dispensed, and used under strict medical protocols outlined by the FDA and cannot be lawfully used for aviation purposes. Oxygen cylinders labeled as AVO, which is aviator’s oxygen, or otherwise is not under the auspices of the FDA and are lawfully used for aviation purposes.
(Reprinted from the Compressed Gas Association)