I had an episode while working on the Railways where a fellow worker was using an Angle Grinder on a length of steel rod without wearing safety glasses, a shard of steel flew from the rod, pierced his eye, penetrated the bone at the rear of the eye socket and lodged into his brain.
He survived, luckily, but is now blinded in one eye and has some mental impairment as well.
Similarly, we were ALL instructed NEVER to use a cutting torch whilst carrying a disposable cigarette lighter in ANY pocket, especially a breast pocket and after seeing an actual piece of footage taken in a workshop where a spark from the metal being cut flew into the pocket, ignited the lighter, causing a blast equivalent to 1/3 of a stick of dynamite, literally blew the entire left side of the workers chest into a cloud of blood, shards of bone and shreds of flesh, killing the worker almost instantly.
A disposable cigarette lighter when full can have the explosive equivalent of approx. 3/4 of a stick of dynamite/gelignite, one half full = approx. 2/3rds that explosive force, 1/4 full = approx. 1/3rd, I've actually done these experiments myself, under very controlled conditions of safety and using buried steel tubing with a wall thickness of 2.5 mms and simply filling the tubes with petrol and igniting it from a very safe distance. The tubes were all torn open very raggedly and almost flattened out completely, imagine, if you will, what it can do to your soft fleshy body.

I'm going to show this at the next Health & Safety Committee meeting.

This would be good to show my students who keep taking theirs off.