Video Depicts 2017 Combustible Dust Explosions at Wisconsin Milling Facility

The Chemical Safety and Hazard Investigation Board (CSB) has released a new safety video based on its investigation of the 2017 explosions at the Didion Milling facility in Cambria, Wisconsin. Initiated by combustible dust, the explosions killed five employees, injured 14 others, and resulted in more than $15 million in damage.

The video uses animation to depict the events at the facility, where corn kernels were ground into smaller components for use in several products. CSB found that the cause of the initial explosion was likely a “smoldering nest” of accumulated corn product in piping. This explosion occurred inside the equipment, generating a flame front that spread through piping to other buildings and sending accumulated dust showering down from overhead surfaces, which fueled another explosion. The spreading fires and explosions ultimately destroyed the facility.

CSB identified multiple safety issues that contributed to the incident. Although many of the products produced at the mill met the definition of combustible dust, CSB found that the company neither understood nor recognized their hazards, and faulted the interconnections between processes for allowing fires to spread throughout the facility. Didion did not perform a dust hazard analysis, and its management of fugitive dust was conducted under a program designed to address food safety, according to CSB. The agency also determined that the safety culture at the facility encouraged workers to regard smoldering fires as routine, affecting their ability to recognize potential hazards.

But even if Didion had performed a dust hazard analysis according to then-current guidelines from the National Fire Protection Association, it might have missed the potential hazard presented by accumulated dust in the equipment where the incident first originated, according to CSB. NFPA has since issued a new standard—NFPA 660, Standard for Combustible Dusts and Particulate Solids—that aligns with CSB’s recommendations to remove equipment exemptions from NFPA’s guidance and require dust hazard assessments for all processes.

CSB also called on OSHA to promulgate a combustible dust standard for general industry, a recommendation the agency first made in 2006. “Robust regulation is absolutely essential to keep tragic incidents like the one at Didion from happening again,” said Sylvia Johnson, a CSB board member.

The CSB video is available on YouTube. For more information, refer to CSB’s press release and its report on the Didion Milling incident.