In the U.S. there are two (2) standard fittings used to fill oxygen systems. One is the SAE AS1046, a 9/16-18 coupling nut and nipple, sometimes know as the ‘SCOTT’ fitting. This may also be the ISO standard. Our TA-916-N & TA-916-S transfiller adapters connect the standard CGA-540 fittings to this fitting.
The other is the older, but most common type, a 3/8-24 threaded fitting sometime known as the “AN” type. Our TA-380-N & TA-380-S transfiller adapters connect the standard CGA-540 fittings to this fitting.
Oxygen is oxygen. That is to say that it has to be 99.99% dry in order for it to be pressurized in a cylinder, else it will corrode and rupture. Oxygen is pure by the very nature of how it is produced. Therefore, no mater what the intended use is, oxygen should be as pure as it was the day it was produced. However, no one can continue to guarantee this once bottles go out into the field. This is why the FAA and FDA has come up with a set of min. purity standards for testing oxygen. It is these testing standards that may be the reason many feel that there are different grades of oxygen.