I didn't know charcoal could spontaneously combust. Mostly I was thinking it would break down if exposed to too much moisture and end up useless as fuel.

Coal may be safer, but it is vulnerable to spontaneous combustion as well. I did some tech writing for an 800MW generating station some years ago. They had finely-ground piles of some 100,000 tons in reserve, of the bituminous variety, and were always monitoring for trouble.

I have small amounts stored in buildings, mostly in 5-gallon plastic pails. But the larger volumes are in 55 gallon steel drums, stored outside with tight-fitting lids. (Apparently, by accident, I did the right thing. Go figure.)

Anyway, here's a link about the spontaneous combustion of coal, which seems correct to me. Bonus: anecdote from the coal-fired Titanic at the end, which I hadn't heard before. http://www.saftek.net/worksafe/bull94.txt

wow; we both learned something. Interesting info. thanks.