What Rick said. Oxygen is oxygen, and the same gas is used for aviation, medical, and industrial. All types come from the same high purity stainless steel diaphragm multi-stage compressors.
Aviation O2 is tested for moisture content because the FAA requires it to be dry (so there is no icing at high, cold altitudes). All O2 is created low-moisture, so your local guy doesn't have to do anything other than put it in the right bottle. Medical oxygen, on the other hand, requires purity. So the vessels (bottles) are cleaned more frequently than aviation / welding. Medical O2 has a longer paper trail too - because of the high insurance premium to cover the liability. Also, pure O2 will dehydrate a person - so for medical purposes there is typically moisture added when it's administered.
Welding: Straight from the producer.
Aviation: Straight from the producer, tested (not manufactured) for low moisture content and some insurance liability
Medical: Straight from the producer, tanks cleaned, bunch of insurance. Moisture added when administered (in hospital)
So if you ever need O2, don't bother with ABO (Aviation Breathing Oxygen) or Medical. I've got a stage fill system, BTW, if anybody needs gas.
Have an unstable day!
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