On 02/24/2016 6:30 PM, SnA Higgins wrote:
....

When I was a Junior I told the story to my science teacher. Without
profanity he called my buddy and I a couple of dumb asses and then explained
spontaneous combustion. For the class he made an example. He took a 2
pound coffee can. He drilled a hole on the side near the bottom where he
attached a length of tubing. He put a votive candle inside near the center
of the bottom. Then he poured a ring of cornstarch around the candle. He lit
the candle and put a lid on the can. He blew a short puff of air in the
tube. The ball of fire was big enough to scorch the ceiling tiles!
....

But not spontaneous combustion...that is like the haystack that catches
itself on fire from internal heat buildup from decomposition owing to
having been too damp when put up.

Explosive combustion such as you're describing requires an external
ignition source; here the candle; possibly your cigarette butt in the
story.

Is fortunate you didn't have a "boom!" moment, indeed. Perhaps were
lucky in there being sufficient "dirt dirt" in the mixture besides the
grain dust so that had a high aerial concentration but much of it wasn't
that combustible, who knows...or maybe it "just wasn't your time" yet.

--