I needed to grind a little piece of steel with a hand held grinder in my garage workshop. Whenever I use a torch or grind anything, I always remove the gas cans for the lawn equipment to the outside. Well one time I was in a hurry and a little 2 gal. gas can was a couple of feet away and was almost totally empty just 3 or 4 ozs in the bottom. The can was sealed except for the little vent hole in the top. I figured I just need to give a quick little grind and what the Hell. Sure enough all Hell broke loose. A spark from the grinder somehow found its way through the little vent hole and lit the fumes in the can. It sounded like a small jet engine with blue flame shooting out of the vent hole about 6 inches. I grabbed the can and through it out the garage door (which was open) in the yard, burning my hand. The can didn't blow up but it ran like a jet engine for a few minutes.