Kurt Ullman wrote:

Are some oxygen molecules more pure than other oxygen molecules?

No, but other gasses can be introduced. Even the compressors for
the regular air firefighters have to be carefully maintained. Oils,
etc., can be introduced that cause failure of the seals.

Do compressed air suppliers have different compressors for filling
different O2 bottles from their bulk LOX source supply?

Hasn't it already been mentioned that even welding O2 gas needs to be
just as clean as medical-grade O2?

At least for medical oxygen you pay more because the tests and
tracking requirements of medical oxygen is more expensive.

I'm not convinced that there are any such tests.

Paperwork and barcode scanning? Yes, sure. I can see that. But unless
someone posts something indicating that such "testing" is done, then I
think it's pure speculation that there is this testing step.

These are additional processing steps (at least the
testing and certification).

Testing is the same as certification. So what are these additional
processing steps beyond testing?

Do you work at a compressed air supply company?