When the West Fertilizer Company in West, Texas, blew up on April 17, 2013, killing 14 people, it must have taken Donald Adair, the owner of the plant, by surprise. In his 2011 emergency plan, Adair described the worst-case scenario for his plant as a 10-minute release of gas! Perhaps we don't appreciate the risks posed by dust as well as we do those of flammable fluids.
You must estimate the severity of the risk and then its probability. NFPA 499, "Recommended Practice for the Classification of Combustible Dusts and of Hazardous Locations for Electrical Installations in Chemical Process Areas," lists many compounds that produce combustible dusts. If yours isn't on the list, test according to ASTM E1226, "Standard Test Method for Explosibility of Dust Clouds."
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