"Richard Riley" wrote in message
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Propane tanks are normally rated for 250 LBS.

That rating is normally at 120 degrees. 280 PSI air is probably a lot
hotter than that. It's been too long since I've done ideal gas law
equations, but I seem to remember 250 psi air getting to 300 or 350 F.
At a temperature higher than it's rating, a tank is weaker than it's
rating.

You lost me here. In my experience, 250# air can be any temperature you
want it to be.

Vaughn