SEARSMONT, Maine — Two volunteer firefighters died and 11 other firefighters and two EMS providers were injured after an oxygen-limiting silo exploded during a May 15, 2026, fire at a Maine lumber mill, according to the NIOSH Fire Fighter Fatality Investigation and Prevention Program report F2026-07. The 20-by-60-foot silo contained kiln-dried wood shavings and residual sawdust. Neither facility employees nor responding firefighters recognized that the silo was oxygen-limiting or that its contents posed a combustible dust explosion hazard.
Crews directed water through an opening into the silo’s base for more than 30 minutes. At approximately 11 a.m., firefighters heard a “whoosh” as smoke rapidly vented from the top, and the silo launched into the air as fire erupted below it. NIOSH’s investigation highlights the need for hazard-specific preplans, disciplined accountability and tactics designed for oxygen-limiting silos rather than conventional structural firefighting.
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Key contributing factors
The silo’s hazards were not recognized. The lumber mill had used the oxygen-limiting silo since 1993, but employees and firefighters interviewed by NIOSH did not know that its design differed from that of a conventional silo. Employees also did not recognize the wood shavings and sawdust inside as a combustible-dust hazard, so that information was not communicated to responders. NIOSH noted that ordinary firefighting actions can create dangerous conditions in silos by introducing air, suspending dust or applying an incompatible extinguishing method.
Water was directed into the oxygen-limiting silo. Shortly after arrival, firefighters located a partially melted access panel in a chute beneath the silo and placed a nozzle at the opening, flowing water through a 3-foot hole into the base. Other firefighters later continued the operation as crews discussed using a ladder truck to flow water from above. NIOSH advises that water or foam should never be directed into an oxygen-limiting silo because suppression activities can introduce oxygen and contribute to a combustible-dust explosion or backdraft-type event.
The incident lacked a formal unified command structure incorporating facility expertise. Facility owners and employees remained near the silo and answered firefighters’ questions, but they were not integrated into unified command. NIOSH concluded that a structured exchange of facility information could have improved recognition of hazards, operational limitations and appropriate tactics at this high-hazard occupancy.
The department’s accountability system was not used. The participating departments trained firefighters to place accountability tags on rings at the first-arriving apparatus, but that system was not activated at this incident. After the explosion, individual departments conducted personnel checks, but a complete accountability process did not identify one firefighter as missing until approximately two hours later. His remains were subsequently located near the silo beneath burning material.
Annual familiarization visits did not substitute for a written preplan. Departments had participated in walk-throughs and were familiar with site features, but the first-due department did not have a formal pre-incident plan for the facility. Tactical decisions depended heavily on firefighters’ individual knowledge and memories, without a readily accessible document identifying the oxygen-limiting silo and combustible-dust hazard.
Recommendations for fire departments
Train members to identify silo type and contents before beginning suppression. Firefighters and company officers should know the visual and operational differences among conventional, oxygen-limiting and modified oxygen-limiting silos and treat unknown contents as a significant hazard until verified. Planned entry into a silo also requires confined-space considerations addressed in NFPA 350, Guide for Safe Confined Space Entry and Work.
Do not direct water or foam into an oxygen-limiting silo. NIOSH recommends avoiding actions that admit air, including opening or breaching the silo to directly attack the fire. Crews should establish a collapse zone, consult the silo manufacturer and, when conditions permit, allow an oxygen-limiting silo to smother the fire while the facility maintains an extended fire watch.
Establish command, accountability and hazard-zone control at the start of the incident. High-hazard industrial responses should integrate a knowledgeable facility representative into unified command while maintaining the location and assignment of every operating member. NFPA 1550, Standard for Emergency Responder Health and Safety addresses incident management and personnel accountability practices that support those functions.
Develop written pre-incident plans for high-hazard occupancies. A useful plan should identify silo type and contents, combustible-dust hazards, suppression-system features, utilities, water supplies, collapse zones, facility contacts and tactics that must not be used. NFPA 1660, Standard for Emergency, Continuity, and Crisis Management: Preparedness, Response, and Recovery provides a framework for developing and maintaining pre-incident plans.
Coordinate combustible-dust planning with facility operators. Departments serving lumber mills, grain facilities and other dust-producing occupancies should ask whether the facility has completed a dust hazard analysis and how those hazards are communicated to responders. NFPA 660, Standard for Combustible Dusts and Particulate Solids addresses fire, flash-fire and explosion hazards involving combustible dust and includes emergency-response planning provisions.
Training discussions
- What information must your first-due officer obtain before committing crews to a fire involving a silo, hopper, bin or other bulk-storage enclosure?
- How would your department prevent crews from defaulting to familiar tactics when a high-hazard industrial incident initially appears routine or nearly controlled?
- Does your current accountability process reliably capture members arriving by POV or mutual aid, and how quickly could command identify a missing firefighter after a sudden catastrophic event?
NIOSH: Water application into oxygen-limiting silo preceded deadly Maine explosion by Lexipol_Media_Group
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