The U.S. Chemical Safety and Hazard Investigation Board (CSB) recently offered an update on its continuing investigation into a fatal explosion and fire on July 29 at the Horizon Biofuels facility in Fremont, Neb.
“Preliminary evidence points to a combustible wood dust explosion, a well-known—and completely avoidable—hazard in wood processing,” CSB Chairperson Steve Owens said in a statement. “This terrible tragedy should not have happened.”
The incident occurred at the Horizon Biofuels facility shortly before noon on July 29 after a sudden release of dust or smoke from the tower, which was quickly followed by flames and a major blast that caused significant structural damage. The day shift operator, who had brought his two young daughters to work with him, was trapped inside the collapsed structure and died. The girls, who were in the break room at the facility, were also killed in the explosion.
Emergency responders were unable to enter the building until the following day, when they recovered the bodies of the three fatally injured people. The explosion caused severe damage within the facility, affected vehicles on-site and nearby, and led to road closures that disrupted local businesses for several days.
Several other fires occurred at the facility, and combustible material at the facility has continued to smolder for more than a month.
The CSB’s investigators plan to examine the operations and conditions at the Horizon Biofuels facility, as well as dust control systems, industry guidance for safe dust operation, and regulatory oversight. A combustible dust explosion can occur when specific conditions align that include dust accumulation, dispersion, and ignition within a confined space, potentially triggering a powerful secondary explosion, as was seen at the Horizon Biofuels facility.
The CSB’s ongoing investigative activities include the following:
- Examining the facility’s design, process flow, dust handling, and dust control systems, including cyclones and dust collectors;
- Assessing whether the facility’s site operating procedures and practices met safety standards;
- Interviewing employees, managers, first responders, and others about the facility’s operations, maintenance, and safety practices; and
- Reviewing the conditions at the facility and whether prior audits or inspections addressed combustible dust hazards in the facility.
Conditions at the facility have so far prevented CSB investigators from approaching the building.
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