Managing combustible dust risks in industrial operations

When someone mentions the word dust, many people think of dirty and unkempt spaces. What might be less obvious is that dust, given the right circumstances, can cause explosive damage in industrial facilities.

Many production operations generate finely divided particles (dust). When those materials are organic in nature, such as wood, paper, rubber, grains, food, and also many inorganic metals, the resulting dust can introduce a fire and explosion hazard that may be capable of destroying equipment, rooms, or even entire buildings. Facilities that produce or handle combustible dusts warrant careful evaluation due to the potential for severe fire and explosion losses.

Why combustible dust is hazardous

All organic materials, as well as many types of freshly created metal dusts, can burn if sufficient heat is present. As the size of the fuel decreases, the required heat needed for ignition also decreases. A familiar example is building a campfire where small kindling ignites more easily than trying to light an entire log. Similarly, dust can ignite easily as smaller particles burn faster and can result in more rapid fire spread or more powerful explosions.

When dust is suspended in the air, as in the case of leaking ventilation equipment or a well-intentioned worker blowing dust off surfaces while cleaning, a fast-burning fire ball can result. So fast in fact, a fire can develop very rapidly, which may make it difficult for sprinkler protection to control the event.

When a dust cloud is confined to a piece of equipment or a room/building, a fast-burning fire can result in an explosion. In many combustible dust incidents, this initial explosion may not cause extensive damage; however, it typically disturbs additional dust on nearby surfaces, creating conditions for subsequent explosions. Secondary explosions can result in significant structural damage to buildings.

What industries are at risk?

FM loss data indicates elevated combustible dust risk in the following industries:

• Agricultural, including grain handling
• Chemical, including pharmaceuticals
• Food processing
• Metal working
• Paper manufacturing/printing
• Plastics
• Textiles
• Tire and rubber manufacturing
• Tobacco
• Wastewater treatment
• Wood/furniture

Managing combustible dust risk

Facilities that produce or handle combustible dusts commonly use a Dust Hazard Analysis performed by qualified individuals or organizations with expertise in combustible dust to evaluate potential risks. A Dust Hazard Analysis (DHA) is a systematic review of a facility, its equipment, and processes to assess risks associated with combustible dust. Required by OSHA and guided by NFPA standards, a DHA evaluates dust characteristics, sources, and accumulations, and identifies appropriate control measures.

Addressing combustible dust hazards generally involves a layered approach that includes limiting dust accumulation, managing ignition sources, and applying appropriate protection measures in conjunction with a DHA.

Prevent dust accumulation:

• Prevent the escape of dust by tightening equipment and improving seals.
• Perform regular cleaning of dust accumulations on buildings, including elevated surfaces, as well as equipment, using intrinsically safe vacuums, water wash methods or soft bristle brooms.
• Never blow dust off surfaces with compressed air or blowers as this creates a dust cloud that could ignite.
• Prevent spontaneous ignition of wet organic materials inside equipment by establishing a regular, rigorous cleaning schedule.
• Inspect ductwork interiors and remove accumulated dust to help prevent a fire or explosion from extending to multiple units.

Control ignition sources:

• Implement a hot work permit system for both in-house personnel and contractors that addresses hot work alternatives and controls the conditions under which work is performed.
• Enforce strict smoking controls throughout the facility.
• Conduct electrical preventative maintenance to reduce likelihood of sparks from electrical equipment.
• Review electrical equipment ratings and installations in all areas where dust may be present.
• Maintain dust-handling equipment to eliminate sparks from misaligned or malfunctioning conveyors, mixers, fans, and other mechanical equipment.
• Perform maintenance of all magnetic separators and any equipment used to convey the material past magnets.

Apply protection and mitigation measures:

• Install sprinklers inside equipment and ducts where combustible dust accumulates and/or in dust collectors with combustible filter media.
• Install explosion vents on dust collectors, equipment handling dust, and/or within area where dust may be present. Venting must be designed by qualified personnel.
• Install explosion isolation equipment to direct potential explosions away from critical processes and rooms, including high-speed explosion abort gates, isolation valves, rotary air locks, or high-speed gate valves.
• Install explosion suppression systems or chemical isolation systems where appropriate.

Combustible dust can present a significant yet often overlooked property risk in industrial facilities. When combustible dust hazards are not adequately addressed, fire and explosions can escalate rapidly and result in extensive property damage. Facilities that generate or handle combustible dust can help prevent loss with the help of proactive hazard evaluation, effective dust-control practices, ignition-source management, and appropriate protection measures. When applied together, these measures can significantly reduce the likelihood of combustible dust incidents and limit the potential damage to equipment, buildings and business operations.

Additional resources:

• Understanding the hazard: combustible dust – Contact us to request a copy of this FM guide.
• FM Client Training Center – Learn more about combustible dust through FM’s Client Training Center courses, including hazards of combustible dust and the potential impacts of dust explosions and fires.
• FM Data Sheet 7-76 Combustible Dust – This data sheet provides practical, engineering based guidance for preventing combustible dust explosions and limiting escalation into secondary events.