Originally Posted by codprawn
If it is intended for use with people I should imagine it is very pure.
There is no reason to make a gas pure - just becuase people are handling it. purity and toxicity are not related.
Argon for TIG welding is usually recommended at 99.998% purity. HP grade argon that is used for diving applications is only 99.9% pure. The main differences are the trace amounts of oxygen and water - which are important to welding - but clearly not harmful to us. I would also suspect that the bottled purity from a diving shop may be less than this as they may not purge all the lines / regulators enough.