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According to part five of the Occupational Health and Safety Guidelines, “a layer of dust as thin as a dime dispersed throughout a room can create an explosion hazard.”
How can that possibly happen?
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A dust explosion is a perfect storm of events, and the key word is “dispersed.” Dispersal is one of five things needed before a harmless pile of fine wood dust (sometimes called “flour”) can be transformed into the fuel for a devastating explosion. Experts call it the “explosion pentagon.” If even one element is missing, there will be no blast.
You need the dust (the drier and finer the better) dispersed throughout the air; you need containment—an enclosed space where pressure can build; you need oxygen, which is everywhere; and you need an ignition source—a spark or a flame. The particle size of the dust is critical. As the WorkSafeBC investigation into the Babine explosion explained: “The smaller the particles, and the greater the number of them, the more violent the explosion is likely to be.”
Put this all together and: BOOM!
The primary explosion is relatively small. But it begins a chain reaction; the blast dislodges other accumulations of dust from beams, ledges, walls and machinery in the factory. This dust then mixes with the air, providing the fuel for a secondary and much more massive explosion. And that’s what blows the roof off a building, and can kill or injure people.
It’s not a new phenomenon. In 1795 a dust explosion blew up a flour warehouse in Turin, Italy.
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