A dust accumulation of 1/32 of an inch deep—about the thickness of a dime—covering just five percent of a room’s surface area doesn’t sound like much, but it’s enough to cause a catastrophic explosion, according to the National Fire Protection Association (NFPA).
Although good engineering and safety practices to prevent dust explosions have existed for decades, there are no government standards for general industry requiring and enforcing policies aimed at preventing combustible dust explosions, according to the US Chemical Safety and Hazard Investigation Board (CSB).
The CSB adds that many companies are not taking effective action to control dust hazards. Industries at risk for combustible dust explosions include food production, metal processing, wood products, pharmaceutical, chemical manufacturing, rubber and plastic manufacturing and coal-fired power plant operations.
Angela Blair, a former CSB investigator, says most solid organic materials will explode if the particles are small enough and they are disbursed in a sufficient concentration.
“What is so frustrating about dust explosions is that they are so preventable and I believe one of the reasons that dust explosions continue to occur may simply be a lack of understanding about the materials,” says Blair. “Some of the materials that could form combustible dust, and there are lots of them, could include coal, food products like sugar and flour, pharmaceuticals, many chemicals and even many metals.”
Like all fires, a dust fire requires fuel, oxygen and an ignition sources. A dust explosion requires two additional elements—dispersion and confinement. When the dust is confined within a structure or a piece of equipment, a powerful explosion can occur.
Dust may accumulate on surfaces such as floors, beams, rafters and lights and lie undisturbed for years. If a fire or explosion occurs, this accumulated dust can ignite in a series of explosions, with devastating results.
The chances of a combustible dust explosion occurring are greater during cold-weather months, because low humidity levels can make dust particularly easy to disburse and ignite.
The NFPA says preventing dust explosions involves designing facilities in such a way that combustible dusts cannot accumulate and migrate and performing rigorous housekeeping on a continuing basis to remove any dust that does build up.
The NFPA also recommends:
Vacuuming dust using specialized equipment designed for that purpose. Never use compressed air to clear dust accumulations because doing so can create a dust cloud that could easily explode in the presence of an ignition source.
Paying particular attention to out-of-the-way areas that might not be visible from the floor yet could contain dangerous buildups of combustible dust.
Having a laboratory test the potential for explosion of any materials in dust (powder) form that are present in your workplace.
In addition, your workers need to be trained to recognize and report combustible dust hazards so that they can be addressed before a disaster occurs.