Michael Courouleau is an expert in environmental safety and health in the workplace.
Q: What are some unusual fire hazards in the workplace?
Michael Courouleau: Of course, everyone thinks of combustible chemicals or fuels, but dust is a major fire hazard as well.
Q: What kinds of materials can produce combustible dust?
Michael Courouleau: Coal, carbon, sawdust, fertilizer, cotton, flour, tobacco, soap, even dried blood can be hazardous in dust form.
Q: Are there questions about any material?
Michael Courouleau: Yes, petroleum coke is common in power plants and cement plants. It’s a lower-cost substitute for coal, but the jury is still out on its combustible qualities.
Q: What are the conditions for dust to become combustible?
Michael Courouleau: It has to be suspended in the air at certain densities or a certain concentration.
Q: Historically, how big of a problem has combustible dust been?
Michael Courouleau: OSHA figures show that more than 130 workers have been killed and 780 injured since 1980 in dust explosions.
Q: How recently has a dust explosion happened?
Michael Courouleau: As recently as 2008, at the Imperial Sugar refinery in Port Wentworth, Georgia; 14 men lost their lives in that incident alone.
Q: Have there been any other notable explosion incidents?
Michael Courouleau: Unfortunately, there was a massive explosion at an ADM facility, and another grain-dust explosion in Galveston, Texas, that killed nine workers.
Q: What is the so-called “Fire Triangle?”
Michael Courouleau: Fire occurs when there’s an ignition source, fuel and oxygen. In this case, the dust is the fuel.
Q: Where, then, would the ignition source come from?
Michael Courouleau: It can come from equipment that causes a spark or heat, hot work processes, improper tools, electrical equipment, even improper work clothing.
Q: What are some other examples of dust explosions?
Michael Courouleau: The worst by far was a 1977 explosion at Westwego Continental Grain; it killed 36 people and destroyed 48 or 73 grain silos. Most of the fatalities came from men being trapped in a cinder-block control tower that was crushed by a falling grain silo.
Q: What sort of regulations are in place to prevent this sort of accident?
Michael Courouleau: OSHA has standards for grain handling, and the NFPA has published fire protection standards. Facilities need air monitoring systems, fire hazard protection systems, maintenance and (above all) training programs in the workplace.
Q: What are the measurements for this sort of hazard?
Michael Courouleau: Combustible dusts are measured by explosive severity, maximum explosive pressure and minimum ignition energy.
Q: What other factors are involved?
Michael Courouleau: Those measurements are all tied in to chemical properties, particle size, concentration of the flammable material, and the flammable characteristics of the suspended materials themselves.