related:
working as a (railroad) engineer on a switch job one cold night - about an hour into the shift, an explosion occured near my feet, with shrapnel felt along my shin and up to my knee.
after stopping the engine and rummaging through the metalic bits that lay strewn about (none larger than 1/2 an inch in length x ~1/8" wide), it was noted that some of the bits had pieces of a label still attached to one side. puzzling the them together revealed part of an Rx presciption, then:

!
it seems the previous engineer is asthmatic; his inhaler had slipped from his jacket pocket and onto the strip-heater (which can get rather hot) attached below the window, near the floor, and alongside the seat. i'm sure the canister held on as long as it could before the pressure built up and then
BOOM. ie, no need to finish the coffee i'd prepared to get me going that night...
to summarize:
more of this overly-drawn-out story, and moral:
it happened a second time when a lighter fell from my own pocket some other night... smoking has more than one way to kill, you see.
Virtual Nomad @ California, USA . DBPro V7.5
AMD Phenomâ„¢ X4 9750 Quad-Core @ 2.4 GHz . 8 GB PC2-6400 RAM
ATI Radeon HD 3650 @ 512 MB . Vista Home Premium 64 Bit