Dust Explosion, an explosion caused by the sudden igniting of a mixture of air and a heavy concentration of combustible dust particles. A mixture containing fine dust is more explosive because there is more exposed particle surface.
The flame or spark that sets off a dust explosion can be produced by friction, static electricity, matches, defective wiring, blowtorches, or any open flame. Dust composed of grain, flour, starch, coffee, cotton, coal, sugar, or other organic materials is highly explosive. Certain metallic dusts, such as magnesium dust, are also explosive.
Grain elevators, coal mines, and factories in which food, candy, soap, cocoa, powdered milk, and starch are made are subject to dust explosions. A small dust explosion can shake dust loose and produce another dust explosion. Such a chain of explosions can destroy a large building.
To guard against dust explosions, exhaust fans are used to pull dust into ducts that carry it outside buildings and mine shafts. Machinery is grounded electrically so that charges of static electricity cannot accumulate. Motors and other equipment that produce sparks are shielded so that the sparks cannot escape into the dusty air. Fire extinguishers are provided to put out any flames at once, since these might cause dust explosions.