When I was in college I had a job changing tires on 18 wheelers. The rims were 2 parts with a retaining ring, and you had to bring the whole thing up to over pressure to set the ring. I was told to stand behind the heavy side if the wheel, and reach through the center to inflate the tire because if all wasn't set correctly, the half rim and ring would shoot off and kill anyone standing in front of it. Later I found out that responsible shops put the wheels in a steel cage before inflating them.
A few months after I left that job there was a picture in the Daily News of a guy who was killed doing that job. He was lying on the ground naked. The force of the compressed air blew his clothes off. you can't fool around with compressed air.
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"Everywhere I turn, here I am." Susan Tedeschi