A while ago, I read of an incident with a bench grinder. The owner's son had used it to grind some wood (No comment!) but when owner used it there was a "whoosh" as the sparks from the metal set off the wood dust.
At school, we were warned of the risk of solvent vapours, such as ether, rolling along the bench from point of use to where there was a naked flame, with predictable consequences.
One of the dangers in a Flour Mill, is that of the dust exploding, (flour is a hydrocarbon, cellulose, so if mixed in the right proportions with air, becomes an explosive mixture)
At various times, experiments have been carried out to run a diesel engine on pulverised coal, working on just that premise. (Thought to be possibility for large main propulsion marine engines) Not too long ago, one of the U S A Railroads tried injecting coal slurry instead of gas oil to run the engines in locos. The problem was the abrasion of the parts of the injection system, (pumps, fuel lines and injectors).
And, given the right conditions, an internal combustion engine can suffer a crankcase explosion, with dramatic, if not lethal, results. One of my former bosses told of crankcase doors weighing 50kg or more being thrown across the shop!
Surprising easy to set oneself, or the surroundings alight, unintentionally.
Howard