Can flour explode?

★ wanayoo — archive 1999 http://howstuffworks.com/question150.htm

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Question

Is flour inflammable? I heard if you were to burn flour it would explode. If so, what is in flour that makes this happen?

Answer

White flour is made up mostly of starch. If you have read the HSW article entitled 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.

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

This link is also useful: Combustability of flour

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