The U.S. Chemical Safety and Hazard Investigation Board (CSB) released a new safety video on its investigation into the fatal combustible dust explosions and fires at the Didion Milling facility in Cambria, Wisconsin, that occurred on May 31, 2017.  Five employees were killed in the incident, and 14 others were injured. The incident also destroyed the facility, resulting in over $15 million in property damage.

The CSB's new safety video, called “Deadly Dust: Explosions at Didion Milling,” includes an animation of the events leading to the incident, and commentary from CSB Board Member Sylvia Johnson and CSB Investigators Melinda Hartz and Cruz Redman.

Didion Milling is an agricultural processing company with several facilities based in Wisconsin. At Didion’s dry corn mill, located in Cambria, Wisconsin, corn kernels were ground into smaller components for use in a variety of corn-based products. The process of grinding corn kernels produces corn-based products and dust as a byproduct. The CSB’s investigation found that both the product and dust can be combustible.

Shortly after 10:30 pm on May 31, 2017, multiple employees at the Didion facility noticed an unusual smell or saw smoke. The CSB determined that the smoke was likely coming from a “smoldering nest” of dust, located inside the corn grinding process. The smoldering nest ignited, leading to a combustible dust explosion within milling equipment and fires that spread to other areas of the facility. Secondary explosions also spread throughout the mill buildings.

The CSB released its final report on its investigation in December 2023. The new safety video covers five of the thirteen key safety issues identified in the CSB’s report that contributed to the incident: process hazard recognition, dust hazard analyses, fugitive dust management, process safety leadership, and regulatory coverage of combustible dust. The video also highlights safety recommendations made by the CSB to Didion Milling, the National Fire Protection Association, and the federal Occupational Safety and Health Administration (OSHA).

Among other important issues, the CSB’s report and the new video point out that since 2006, the CSB has called on OSHA to develop an overarching standard on combustible dust for general industry. OSHA has yet to issue a combustible dust standard, however.

Board Member Sylvia Johnson states, “The CSB has been calling for a comprehensive standard on combustible dust for many years to help prevent tragic, deadly incidents like the one at Didion from continuing to occur.  Robust regulation is absolutely essential to keep these incidents from happening in the future.”

The CSB is an independent federal agency charged with investigating incidents and hazards that result, or may result, in the catastrophic release of extremely hazardous substances. The agency’s core mission activities include conducting incident investigations; formulating preventive or mitigative recommendations based on investigation findings and advocating for their implementation; issuing reports containing the findings, conclusions, and recommendations arising from incident investigations; and conducting studies on chemical hazards.

The agency's board members are appointed by the president subject to Senate confirmation. The Board does not issue citations or fines but makes safety recommendations to companies, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA.

For more information, visit www.csb.gov.