From Plain Flour to Flame Power: Watch Out for Dust Explosions!
We handle TNT and gunpowder very carefully, for obvious reasons. But do you take the same care with flour or powdered milk? Not many people know that some everyday types of powder can be explosive.
Even a seemingly harmless powder can ignite (check out this video). It is not only powdered milk: also flour, icing sugar, corn starch, wood sawdust, instant coffee, animal feed, etc. can cause a dust explosion.
How does a dust explosion occur?
Any explosion requires three things: fuel, oxygen and heat. When a cloud of combustible dust - with plenty of oxygen among the particles - is suspended in the air, all it needs is heat to ignite the particles. That heat could come from a flame or spark.
The principle is simple: the finely distributed dust burns very intensely because it is well mixed with the oxygen it needs for combustion. So it is important to get that particle-oxygen ratio right.
How dangerous is a dust explosion?
A dust explosion is similar to a gas explosion, but more treacherous. This is because the initial explosion often leads to further explosions: the primary explosion can create new dust clouds. This can result in a chain reaction of dust explosions, and the secondary dust explosions are usually more violent than the primary ones.
How big is the risk of a dust explosion?
In an industrial environment where large amounts of powder are handled, or in silos where large amounts of powder are stored, there is a high risk of dust explosions. These are places where anything that can generate a flame or static electricity has to be strictly controlled.
However, the flour in your kitchen is very unlikely to burst into flames. As long as you don't start throwing bags of flour in the air and then holding a match underneath. (Seriously: don't try it!)