Ed Pawlowski wrote:

I know how a medical tank was handled. I don't know anything
about a welding tank. The oxygen may be pure going in, but I
don't know what was in the tank beforehand.

So you are speculating that the average compressed-gas retailer
or supplier does not perform the same steps to evacuate / clean
/ what-ever / a welding tank that he (or you) does with a medical
tank.

I'm not speculalting; you are.

I've never stated either why what I think is done to returned welding
tanks prior to getting refilled.

The worst case situation is to assume that no special treatment is done
to them. They are simply connected to a compressor and they are
re-charged with O2, and probably using the same equipment, the same
valves and lines and the same source of O2 that are used to fill all O2
tanks that are sold or rented at that site, which could be for welding,
medical, or aviation use.

I said I did not know but you are trying to twist that. .

I said several times that you are proceeding from a point of view that
the handling and processing of returned welding tanks IS different from
that of medical tanks.

Let me ask you this:

If, hypothetically speaking, a compressed-gas supplier handled and
processed ALL returned O2 cylinders the same way (both welding and
medical cylinders) - which is to say that they are always cleaned,
evaculated, etc, according to medical-grade specifications, then what
would be your argument that an end-user shouldn't purchase a tank of
"welding grade" O2 for their own medical or veterinary purposes from
that supplier?

If it does not have that piece of paper, it is not medical oxygen.

I agree that selling a tank of welding O2 to someone as a medical-grade
tank of O2 (and charging medical-grade prices) is wrong and probably
violates all sorts of laws and insurance policies.

But we are not talking specifically about that situation (product
fraud).

If I buy welding O2 specifically for medical purposes, I agree that I am
taking some sort of risk that I have no recourse or remedy for should
the tank contain some harmful impurity. But I'm not convinced that a
medical tank has a lower probability of containing a harmful impurity
compared to a welding tank. The difference is that when I pay more for
a medical tank, I am in effect buying an insurance policy that allows me
to seek financial compensation. Perhaps I see no value in that
additional cost if the odds of any tank (welding or medical) containing
a harmful impurity are extremely low.