Quote (JDH @ 20 Mar 2014 16:54)
you dont know how deep the rust may be and it might eventually develop a pinhole that leaks gas out. that would be highly dangerous.
That's my concern, actually. I don't want to turn in a potentially rusty tank, if it's just gonna go back into circulation.
On the part of the businesses taking in the cylinders for exchange, I don't know what kind of quality control they run, or if there's some kind of standard for testing tanks, before they're refilled.