I'll never forget my first day on the job working in a data center... one of the guys lost a finger
that facility had really shitty cooling (and let's be honest, my stupid company waaay overloaded things. they didn't believe in leaving space between servers, cables were ran everywhere -- including under the floor where the AC was being pumped in from -- it was a total mess). to help out with the cooling, they had big industrial fans blowing down the hot rows.
common sense would dictate that if you're going to move a fan that size, you turn it off, wait for it to spin down, and then move it. instead, the guy moved the fan while it was still spinning away on high, and his finger slipped through the grate D: