Why is grain dust in elevators explosive?

Just about any organic material will explode if it is fine enough, dry enough, in suspension in air, and confined. All it takes is the fuel, oxygen, and a spark.

Sugar, coal dust, wood dust, walnut hulls, the ingredients of children’s modeling dough, and some medications have also been involved in recent dust explosions. Organic particles vary in flammability, and wheat starch and cornstarch are more explosive than other kinds.

Often a primary explosion shakes the building, dislodging more dust, which ignites in turn. There is also a pressure wave ahead of the flame front that shakes loose still more dust.

The stronger the elevator, the greater the danger —a stronger container lets pressure build up so that when it is finally released, the force is much stronger.

Proper venting to relieve pressure is one important safety measure.

Others are cleaning grain of foreign material and broken kernels before storage, spraying edible mineral oil on conveying equipment to control dust, and installing pneumatic dust-collection systems using bag filters.