Combustible Dust Incidents, 2006–2017
The U.S. Chemical Safety and Hazard Investigation Board is examining potential dust sources that might have contributed to the fatal May 2017 explosions at the Didion milling facility in Cambria, Wis. In an ongoing investigation, the agency is reviewing witness testimony, post- incident damage patterns, and computer modeling of the propagation of fire and explosions in the mill. Moments before the explosions, workers reported seeing dust clouds suspended in the air inside the facility. The explosions occurred at night, when only 19 workers were present. Five of the workers died, and the other 14 were injured. The Didion incident prompted CSB to issue a “call to action” on combustible dust. The agency sought comments on the management and control of combustible dust from individuals and entities involved in the safe conduct of work within inherently dust-producing environments. An article in NewsWatch discusses the agency’s efforts related to combustible dust. The incident at the Didion facility was one of six dust incidents that occurred in 2017, according to CSB’s incident screening department. The agency recently released data on 105 dust incidents that occurred between 2006 and 2017. Information based on this data appears below.
From CSB’s investigative update on the 2017 explosions at the Didion milling facility: “Dust explosions are typically classified as either primary or secondary. A primary, or initial, explosion can trigger secondary explosions when combustible dust or fines [particles smaller than 75 microns] that have accumulated on floors or other surfaces are lofted into the air, or when either is thrown into the air from damaged equipment, and ignites. If a sufficient volume of dust or fines [is] lofted or secondary releases occur, a relatively weak primary explosion can trigger very powerful secondary dust explosions.”

Chemical Safety and Hazard Investigation Board: Combustible Dust Hazard Investigation (November 2006). Chemical Safety and Hazard Investigation Board: “Dust Incidents, 2006–2017” (PDF, October 2018). Chemical Safety and Hazard Investigation Board: “Factual Investigative Update: Didion Milling” (PDF, April 2018).
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In August, The Knoxville News Sentinel reported that a student intern and a researcher at Oak Ridge Associated Universities had devised an experiment to replicate the McCluskey incident in order to study the effects of radiation on the body. By irradiating vials of their own blood for different lengths of time, the researchers hope to generate data that clinicians and first responders can refer to following an exposure incident.

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