Flour Bomb

From Wikipedia:

The classic educational flour bomb demonstration shows the explosive power of flammable powders under the right circumstances. Given a large enough suspension of combustible flour or grain dust in the air, a significant explosion can occur. An example is the 1998 explosion of the DeBruce grain elevator in Wichita, Kansas, which killed 7 people. [1].

Almost any finely divided organic substance will produce an explosive mixture in an air suspension. For military use, so-called hyperbaric or thermobaric fuel-air bombs have been produced that work by initially creating a mist of jet fuel (kerosene) or diesel fuel, then igniting the mist. The resulting explosion not only destroys structures, but depletes the atmospheric oxygen in the immediate vicinity, as this type of bomb does not use an explosive that contains its own oxidizing agent. Hyperbaric bombs are designed to produce maximal overpressure, and hence structural damage; whereas thermobaric bombs are designed to produce a very high temperature in the zone of explosion/combustion.

Very fine flour is dangerous in air suspension, as it too can explode. This is a significant risk when milling grain to produce flour, so mills go to great lengths to remove sources of sparks. These include carefully sifting the grain before it is milled or ground to remove stones which could strike sparks from the millstones, and the use of magnets to remove metallic debris which can also strike sparks.