Can Flour Explode?

Just about any carbohydrate dust, including sugar, pudding mix and fine sawdust will explode once ignited.
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White flour is made up mostly of starch. If you have read the article How Food Works, you know that starch is a carbohydrate, meaning that it is made of sugar molecules chained together. Anyone who has ever lit a marshmallow on fire knows that sugar burns easily. So does flour.

Flour and many other carbohydrates become explosive when they are hanging in the air as dust. It only takes 1 or 2 grams of dust per cubic foot of air (50 or so grams per cubic meter) for the mixture to be ignitable. Flour grains are so tiny that they burn instantly. When one grain burns, it lights other grains near it, and the flame front can flash through a dust cloud with explosive force. Just about any carbohydrate dust, including sugar, pudding mix, fine sawdust, etc., will explode once ignited.

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When you hear about an explosion in a grain elevator on the news, this is what has occurred. A spark or a source of heat ignited the dust in the air and it exploded.­

Originally Published: Apr 1, 2000

Flour Explode FAQ

Is flour highly flammable?
Yes, when flour is hanging in the air as dust, it will explode if ignited. Anything that's powdered and suspended in the air has far more surface area exposed to oxygen per unit weight, which can easily cause an explosion. In fact, there have been well over 100 reported explosions in food processing plants in the United States since 1994.
What causes flour to explode?
Flour grains are so tiny that they burn instantly, lighting other grains near it and causing the flame front to flash through the dust cloud with force.
Does flour explode in microwave?
If the flour has been mixed with wet ingredients (i.e. a microwave mug cake), then you have nothing to worry about. Similarly, since flour isn't prone to explode on its own, unless you're throwing flour in the microwave, creating a cloud of flour dust, and quickly turning the microwave on, it likely won't explode. However, we don't suggest at-home experiments like this.
What other food dust explodes?
Pretty much any carbohydrate dust will explode if ignited, including sugar, pudding mix, powdered milk, and cocoa.

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