Thursday, December 7, 2023

Review - CSB Publishes Didion Milling Investigation Report

Yesterday, the Chemical Safety Board (CSB) published their final report on the Didion Milling explosion and fire that occurred on May 31st, 2023. This combustible dust incident resulted in five employee deaths and an additional 14 employees injured (100% of 19 employees working at the facility at the time of the incident). The incident resulted in $15 million in damages, with no off-site damage or injuries reported.

Safety Concerns

The CSB report identified safety concerns that contributed to the incident. These include:

• Process Hazard Recognition,

• Dust Hazard Analysis,

• Engineering Controls for Combustible Dust Hazards,

• Structural Design for Combustible Dust Hazards,

• Fugitive Dust Management,

• Management of Change,

• Incident Investigations,

• Process Safety Information,

• Management of Audits and Inspections,

• Emergency Preparedness,

• Personal Protective Equipment,

• Process Safety Leadership, and

• Regulatory Coverage of Combustible Dust.

While these safety issues are discussed in detail throughout the report. CSB provides a summary of these issues on pages 173 - 183.

Safety Recommendations

This report concludes (pgs 183 – 186) with thirteen recommendations that could prevent the reoccurrence of an incident such as this. These include nine recommendations for Didion Milling, three for OSHA, and one for the NFPA.


This is another of a long line of comprehensive reports from the CSB. It provides a detailed review of the processes involved and an in-depth discussion of the process safety management shortcoming that inevitably led to the incident. Interestingly, it does not, however, mention the criminal investigations and convictions of four Didion management employees for falsification of records related to the facility’s cleaning logs that I reported on in October. Safety oversights and misunderstandings are a large enough problem to overcome to prevent serious chemical incidents, but adding criminal malfeasance to situation is sure to exacerbate safety problems.


For more information about the details of this report, including a brief look at other combustible dust reports by the CSB, see my article at CFSN Detailed Analysis - - subscription required.

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