I just remembered that I was once responsible for a potentially life threatening laps of intelligence with compressed air.
In about '78, my employer bought a used 4' kick sheer that had been converted to pneumatic by a previous owner. When it arrived it had a 4x4 lagged under each support leg. I figured they were there for transport purposes only and removed them (the importance of this will soon be clear). The sheer was in rough shape so I took bits apart and made adjustments/repairs as I thought appropriate. After reinstalling the air cylinder and treadle, I decided to use air to retract the cylinder. I put a nipple on a hose from the cylinder and plugged it in to shop air.
!!! BAMMM !!! The cylinder EXTENDED and the treadle hit the floor causing the machine to flip onto it's back. !!! BOOM !!!
The 4x4s were needed to clear the travel of the modified treadle. And, obviously, yours truly charged the wrong hose.
People came from distant parts to see WTF? No physical injury befell any persons (thank God) or the sheer (small dent in the concrete floor).
My embarrassment hit a new record high and I suffered additional discomfort from the massive, instantaneous injection of education. That was bad, but I feel much better now.