Attached is a picture of the remains of a pump house (water) at a coal mine. Unknown to anyone before the explosion, methane gas was coming up around the well casing. When the pressure switch called for water & the contactor closed, you can see the result. Luckily, no injuries.
If you think this is bad check out the following. SA mining is very dangerous, they dont measure "Number of shifts without an injury" like OSHA does they measure number of shifts without a fatality http://www.pitt.edu/~ethics/South_Africa/case.html