Almost got killed working on a charged air brake.
Back in about 1962 I was pulling a set of doubles, hauling tomatoes out of the Chico Bean Growers in Northern, CA. I was a real green truck driver and when I found a brake pot on the rear axle of my rear trailer leaking I called my boss, the owner of the truck. He instructed me, by phone, to replace the diaphragm. His instructions were not that clear and did not have the warning that you guys are rightly giving readers of this forum.
I released the air pressure to the trailer brake and replaced the rubber diaphragm. The cap was held on with a two-bolt clamp. After I charged the lines by moving the trailer brake lever full on. (that was close to 120psi) I checked the device for leaks. There was just a whisper of air so instead of draining the air lines I proceeded to use a wrench to tighten the charged pot clamp. You guessed it! I found myself 20-25 ft from the trailer in dust about 6 inches deep with my forehead split wide open and blood everywhere. When I put my hand to the wound all I could feel is a big pulpy mass which I actually thought was my brains. Some people put me in an old pickup and drove me, while I was holding my 'brains' inside my head, to the Chico Hospital. It turned out that my "brains" were just a pulpy mass of flesh where the clamp hit and and ripped everything off to my skull. After a lot of cleaning my forehead skin was reattached and stitched back in place. An xray revealed no fracture and, what the doctor said, one of the thickest skulls he had ever seen.
After a couple of weeks of rehab I was released back to work. Because the stitches were put in properly I never needed plastic surgery.
I know all of the jokes this little story will generate but I can tell you the best outcome. I have a tremendous respect for anything air-powered and assure you that there is NEVER a short cut when working on this equipment. Next time you see me check out the scar on my forehead that runs from the top of my nose to the hairline. I am truly lucky to be alive.
Mind all the good advice given in this forum about safety. We don't need any more statistics.