During World War II, Hitler's air force kept bombing Britain with bombs falling from the sky. The owner of a flour mill in England was secretly glad that the bombs did not hit his plant, but almost simultaneously with the bombs falling, there was a big explosion in the workshop itself, and the roof flew up into the sky, and the force of the explosion exceeded the destructive effect of the bombs. At the same time, several other flour mills exploded.

This peculiar explosion cost the mill a lot of money and was inexplicable because no bomb fell on the plant, and besides, there was only flour and machinery in the workshop, and no explosives like dynamite.

Because the air wave of the bomb explosion lifted the flour dust in the workshop, so that the flour contained in the air reached a certain concentration, and the explosion occurred when the fire. The explosive was flour.