I worked in the elevator industry in NYC and was sent to rehang two basement elevator shaft doors that were blown into the pit. When i got there PD and FDNY told me that this happened is because someone threw an empty hair spray can down the garbage chute and it became a bomb. At that time they were still burning the waste in NYC apt. buildings and because the incinerator room was opposite the elevators the exploding can became a bomb and was the cause of the elevator doors being blown off. Bottom line is these things are dangerous.