At approximately 7:37 on August 2nd, 2014, a flour factory exploded, injuring and killing several people. But how did an explosion happen without explosives—was it just due to dust? To understand, let’s start with a little story.
During World War II, as Hitler’s air force bombed the UK, the owner of a British flour mill felt relieved that no bombs hit her factory. Yet almost the moment a bomb landed nearby, a massive explosion ripped through the workshop, sending the roof flying. The blast’s force even exceeded that of the bomb.
Why does flour explode? Here’s the science:
When a grinder crushes wheat, the electrical energy it uses converts to “surface energy” stored on the flour particles.
Finer particles mean a larger surface area and more surface energy.
Crushed into flour, this surface energy can reach 2.7×10⁶ joules—equivalent to lifting an object 2,700 meters high. That’s a 100-million-fold increase in surface energy.
With such high surface energy, dust readily releases energy through physical or chemical reactions. When tiny dust particles mix fully with air and encounter a spark, they react violently, releasing huge energy in an instant—causing a dust explosion.
Flour isn’t alone: combustible dusts like cocoa, cork, wood, rubber, leather, and plastics can explode. Even organic compounds and inorganic materials such as sulfur, iron, and cobalt pose risks. When these reach a critical concentration in the air and meet an open flame, even a tiny spark can cause explosion.