We used to take a half-full can of gas, then get a ping pong ball, drill a hole in it, fill it with bleach, then put tape over the hole. Drop the ping pong ball in the gas can, screw the lid on really tight, then wait. It used to take about 10 minutes for the gas to eat its way into the ping pong ball, but when it did, and the bleach mixed with the gas... boom! The scary part is only worked, maybe, half the time. So there would be cans of gas/bleach just sitting in a field, waiting to explode or release really harmful chems into the air. We were kids, young and stupid.