You Are Out Of Your Mind
I feel I have to reply to this before someone gets killed.
It is true to say that the O2 source is the same for all 3 commercial grades of O2, that is Welding (industrial), Medical and Aviator grade, this is where the similarities cease.
For medical and aviator grade, the cylinders are drawn into a vacuum before refilling and with the case of aviator grade it is also further dried.
The big hazard with using welding grade is that any contaminants, such as CO, CO2 and N2 remain in the cylinder as well as the big no no which is water.
The aviator and medical grade are certified and analysed to be minimum 99.5% O2, we have seen welding grade produce results of 94% O2 (we did not want to know what the other 6% was.
The main problem is the water in the system, so far as aviation is concerned. This can and will turn to ice when pressure is released, particularly at the low temperatures experienced at altitude and will result in poor performance of downstream regulators or even stop them functioning totally.
Coupled with this you also have the long term risk of corrosion etc.
I hope that this is clear!
Tex