Sparks = fire = explosion.

There are a lot of safety precautions you need to take in a shop. For example, you can’t have a bunch of oily rags stacked on top of each other because they have a tendency to spontaneously combust. Pretty crazy, huh?

Another precaution you need to take is being very, very aware of where you’re shooting sparks. If you’re grinding something metal, the sparks are going to fly, and if they land on something flammable, something like this can happen: