Dust-free mills and elevators are explosion-proof. Carelessness - a lighted match, dusty machinery, an uncovered candle or lantern, friction in machinery. Cleanliness - means nothing to explode, protects workmens' lives, saves property, saves food. U.S. Grain Corporation, U.S. Department of Agriculture. For further information about grain dust explosions write to the Bureau of Chemistry - U.S. Department of Agriculture.