ugh! I've had mine get caught inside a printer before, and that was not good! Moving parts, gears and high voltage all too close for comfort. Now when I'm going to be working inside a "live" printer, I usually take off both my ring & my watch.
We had posters all over the hangar when I was in the Army of 2 things: Beware of FOD (Foreigh object damage, i.e. a cotter pin in a jet engine), and pictures of a left hand cut down to the bone. Watches, rings, and dogtags all come off when you go higher than ground-level.
saw medical posters of a guy whos ring got caught jumping out of a rolling vehicle, ripped his tendon IN HIS HAND which followed the severed digit out and off of his body. Surgical scar went from ring finger down to wrist.