From Dust to Disaster Understanding Combustible Dust Hazards

Fine, ordinary-looking dust can accumulate quietly on beams, equipment, and floors until a single disturbance turns it into a devastating hazard. Combustible dust explosions have destroyed facilities, shut down operations, and taken lives, often in industries that never considered themselves “high risk.” From food processing and agriculture to metalworking and plastics, explosive dust hazards exist far beyond heavy manufacturing. Understanding this risk is the first and most important step toward preventing a catastrophic event.

What is combustible dust?

Combustible dust is fine particles of solid materials such as plastic, rubber, fertilizer, metal, chemicals, grain, wood, paper, sugar, food and animal feed. The danger arises when this dust becomes airborne and mixes with oxygen, creating an explosive atmosphere. Dust is fuel. The air includes the oxidizer. Now all you need is an ignition source for a tragedy to occur.

A combustible dust explosion requires five elements (the Dust Explosion Pentagon):

The Science Behind the Danger

1. Fuel (dust)
2. Oxygen (the air)
3. Ignition source (bearings, light bulb, electric motor, etc.)
4. Dispersion (the cloud of dust in the room)
5. Confinement (an enclosure such as a room, piece of equipment, or ductwork)

On July 29, 2025, a wood dust explosion at Horizon Biofuels killed an operator. The incident began when a release of wood dust from one of the buildings ignited, triggering an explosion and structural collapse. This was compounded by the fact that the operator had brought his young daughters to work that day. They were in the breakroom when the explosion occurred killing the children and their father.

Prevention

The first steps to preventing dust explosions are understanding what types of dust are present in your environment, where they are generated, and how hazardous they may be.

For example, sugar mills, feed milling, dry food production, storage, and transfer operations can produce significant amounts of combustible dust. These processes typically represent the highest-risk areas in the facility.

Next, determine the severity of the hazard. Ask key questions:

• Is dust generated in large quantities?
• Is it accumulating on surfaces or equipment?
• Are there hidden or hard-to-reach areas where dust may collect unnoticed?
• Is there any equipment that is hard-to-reach and can generate heat, such as switches, motors, and bearings?

Dust layers of 1/32 of an inch or more, about the thickness of a paperclip, are considered excessive. When disturbed, this accumulated dust can become airborne and create conditions for a fire or explosion. A small dust explosion can then cause more dust to become airborne, resulting in a larger conflagration through the facility.

Once identified, combustible dust hazards need to be addressed using the hierarchy of controls, starting with Engineering Controls and working your way down to personal protective equipment (PPE).  Eliminating the hazard through engineering controls is always the best practice. This could involve changing the process to eliminate or reduce dust generation as much as possible. The dust that remains must be controlled. Depending on the process, this may include exhaust ventilation, mineral oil systems, ducting, and effective housekeeping. Each of these controls has the potential to introduce additional hazards that must also be addressed, particularly in ducting which can remove dust from the area but then accumulate within the ductwork or elsewhere. Using the right types of lighting, tools, and machinery is critical to control potential ignition sources in potentially explosive dust environments (Class II).

Combustible dust incidents are preventable, but only when the hazard is recognized. Dust that is allowed to accumulate, migrate, or remain hidden creates conditions where a minor event can escalate into a fire or explosion. Awareness leads to better housekeeping, smarter inspections, and safer decisions. By identifying dust hazards early and addressing them consistently, organizations can protect their people, their property, and their operations from this significant, but often misunderstood hazard.

More from MEMIC

• Safety Experts Podcast: Combustible Dust in the Workplace - What We’ve Learned and What’s Changing with James Burke

Other Resources

• OSHA Fact Sheet - Combustible Dust
• AIHA: A New Tool for Preventing Combustible Dust Incidents
• NFPA 660 Standard Development