[billorites]

Medical oxygen and aviators oxygen are both 100% O2.

They are not the same thing though and are not interchangeable.

The only significant difference is that aviators O2 is certified to be dry and to have no water vapor in it. Medical oxygen can and does.

You don't want aviators oxygen fittings and stuff freezing up in the cold at high altitudes.

[Eaker]

We called it five-nines dry.