Might have told this before. My wife's step father work in a metals plant during WWII. They were making magnesium parts for planes. As the story goes, they had to periodically clean magnesium dust from the machine shop air ducts. They sent the new guy to do it. He did, covered with dust. Then it was break time and he went for a cigarette. While folks yelled NO - it was too later and he went up like a road flare as folks ran and jumped out windows (whatever). Looked like a cinder afterwards.
Another, two jobs ago - the gym had collapsible, folding bleachers, heavy wood and pipe construction. A workman was doing something to them and was inside the structure when it activated and folded up. Dead.
About the disposal - once in a while something gets grinded and stuck - like a can pop top. Down to the basement and throw the circuit breakers before dealing with it. Same with other electrical things. As a kid, I stuck a metal nail file into the wall socket - ouch.