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Slow-Motion Mayhem Video Sets Flour Aflame [video]

The views expressed are those of the author and are not necessarily those of Scientific American.

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First, please enjoy this video of “Stupidity Captured at 2500 Frames per Second,” preferably in full-screen view at high resolution. Take special note of the “Flour + Candle” segment that starts around the 2:50 mark:

If, like me, you were left wondering how and why ordinary cooking flour would ignite in a giant fireball, allow me to share with you the strange science of explosive dust.

We don’t ordinarily consider all-purpose flour to be a flammable, and indeed, a cup of flour sitting on the kitchen counter poses no danger. Yet flour does contain calories, and calories are just another form of energy.

Fires require just three factors—fuel, oxygen and heat—and our cup of flour can’t get enough oxygen to burn. Throw that flour into the air, however, and it disperses into a fine haze of dust particles. All these tiny particles have a huge surface areas compared to their volumes, which means there’s a lot of oxygen surrounding each bit of grain. Add a spark—or, in this case, a candle—and our fibrous fuel turns into a fireball.

The problem becomes most acute in grain silos or other industrial settings, where fine dusts collect in confined spaces. Here an errant spark—or even static electricity—can set off a massive explosion. In the late 1970s a spate of explosions in grain elevators killed 59 people. Agricultural grains aren’t the only danger. Dust is a constant worry in coal mines, and anything from sawdust to aluminum to powdered milk can ignite under the right conditions. In the first two months of 2003, a dust explosion in a Kentucky acoustic insulation manufacturing plant killed seven, while six died during a polyethylene dust explosion in a North Carolina pharmaceutical plant.

As the video says: please do not under any circumstances try any of this at home.

flour fire, explosion, dust

(via kottke)

About the Author: Michael Moyer is the editor in charge of space and physics coverage at Scientific American. Follow on Twitter @mmoyr.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. notafraidofthetruth 8:18 pm 04/19/2012

    Calories are not a form of energy.

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  2. 2. Mr. Natural 10:39 pm 04/19/2012

    Calories are indeed a form of food energy.

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  3. 3. rushil2u 10:50 am 04/20/2012

    The calorie is a measure of energy, just like the joule. The ‘calorie’ rating we usually see on food packaging is actually kilo-calories (kCal).

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  4. 4. DrKrishnaKumariChalla 10:30 pm 04/20/2012

    I don’t like this destroying things to capture the process in slow motion on a video. Haven’t you heard about carbon foot prints? Using too much of natural resources is bad enough. Destroying things for entertainment is worse.And for studying things scientifically? Lame excuse!We are not so dumb as not to understand why flour ignites. Mere mentioning is enough.

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  5. 5. sarunamii 12:59 pm 03/13/2013

    It seems like it’s the most common things around us that we don’t always realize how dangerous they can be. Thank you for your article.

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