Dust is a nuisance, but did you know that some dust can cause explosions? This is called “combustible dust.”
Combustible dust has caused deaths and injuries, and destroyed entire buildings. Here are a few real-life examples of how dangerous combustible dust can be:
In 2015, 15 concertgoers were killed and 500 were injured at a waterpark dance party in Taiwan. The event released dyed cornstarch into the air to create a colored fog effect. The dust saturated the stage and was ignited by a spark. The surrounding dust-filled air erupted in a flash fire, engulfing everyone in the area. Many of the deaths happened months after the incident due to extreme burn injuries.
In 2010, four workers were killed after a titanium dust explosion at a metal recycling plant in West Virginia. Metal dust created in the recycling process settled inside the plant’s metal blender machines and surrounding air. A blender malfunctioned, creating a spark that ignited the metal dust buildup inside the bin. Flames inside the blender bin traveled up the walls in a flash fire. As the flash fire burned, metal dust floating in the air ignited, causing the recycling plant to explode.
In 2008, 14 workers were killed and 38 were injured in a sugar dust explosion in Georgia. The company processed and bagged sugar products through a complex network of conveyor belts, chutes, hoppers and mills. Over time, the floors and machinery became covered in sugar. Employees would use canned air to clean the sugar off internal machinery, sending sugar particles into the air. The sugar particles would then settle on hard-to-reach pipes overhead. Eventually, sugar dust built up inside chutes below the main floor of the plant. When a conveyor belt malfunctioned, the gears created a spark, igniting the sugar dust in the chute. A flash fireball ripped through the foundation, sending more sugar dust into the air. This created a chain reaction of secondary explosions and fire.
What is combustible dust?
The Occupational Safety and Health Administration (OSHA) defines combustible as “fine particles that present an explosion hazard when suspended in air under certain conditions.” Combustible dust can cause flash fires, explosions and fires. There is a difference between these terms. One or all three can be present in combustible dust incidents:
Flash fire
A flash fire is a sudden and intense fire caused by a spark (fuel source) inside a mixture of air (oxygen source) and a dispersed flammable material (fuel source). The fuel source could be gas fumes or fine combustible particles. Flash fires may ignite and dissipate quickly, as a flash.
Sometimes, the air is so saturated the flash fire burns longer. If the area is contained or flammable materials are in the flash fire’s path, things become even more dangerous.
Explosion
An explosion is when the combustion process transitions from a flash fire to a detonation. The shock wave produced by the blast moves faster than the speed of sound. Explosions typically occur when the flash fire is confined to an area or building, like a manufacturing facility. Pressure from the blast triggers a sudden release of energy in the form of a shock wave that blows apart whatever contained it.
Fire
A fire is a reaction between a substance and a gas that releases heat and light. Fires usually involve solid combustibles, like wood or paper. But they can also involve liquids or gases. During a flash fire or explosion, other flammable materials may catch fire and burn much longer than the flash fire or explosion.
What are the conditions needed for dust to combust?
According to the National Fire Protection Association (NFPA), here are the conditions required to create a fire, flash fire and explosion:
To create a fire, you need three things:
- fuel
- oxygen
- an ignition source
For example, let’s say you stack a pile of dry kindling wood (fuel) in a pit in the open air (oxygen), and you drop a lit match (ignition source) on the pile.
To create a combustible dust flash fire, you need four things:
- fuel
- oxygen
- an ignition source
- dispersion
Let’s take the kindling wood example further. You crush the kindling wood into fine dust and throw it into the air over a flame.
To create a combustible dust explosion, you need five things:
- fuel
- oxygen
- an ignition source
- dispersion
- a contained area
Let’s say you crush the kindling wood into fine dust and put it in a metal container. You use a blower to disperse the dust throughout the container. Then, you light a match and throw it into the container.
Watch the NFPA’s “What Is a Combustible Dust Explosion?” video to see how combustible dust explosions work.
Examples of combustible dust sources and industry operations
Combustible dust can come from various sources, including materials such as:
- Coal
- Wood
- Pulp
- Rubber
- Grain
- Sugar
- Flour
- Spices
- Grain feed
- Plastics and plastic processing operations (like industrial 3D printing)
- Metals and metal processing operations (like recycling)
- Chemicals
- Textile fiber
According to OSHA, industries with the highest combustible dust-related fatalities and catastrophes are:
- Farm suppliers
- Grain processing facilities
- Animal food manufacturers
- Food processing facilities
- Industrial bakeries
- Sawmills
- Wood manufacturers
- Institutional furniture manufacturers
- Metal window and door manufacturers
- Sheet metal work manufacturers
- Reupholstery and furniture repair operations
- Coal-fired power plan
- Chemical manufacturers
- Recycling facilities
This list is not exhaustive. In fact, the list of combustible dust-related materials and industries keeps expanding as incidents are investigated.
How to prevent combustible dust hazards
If your business processes or handles materials that generate dust, you are susceptible to combustible dust hazards. Combustible dust can be a hidden hazard, making it even more dangerous. Dust can form on surfaces like overhead beams, inside ventilation systems, on top of equipment and in hard-to-reach places.
Evaluate your operations
You’ll need to assess whether your operations produce fine dust and take action to reduce it. If you can see dust floating in the air or on surfaces, you have a dust problem. Frequent equipment malfunctions can also indicate a dust problem. If your employees complain of breathing difficulties or eye irritation, you have a problem.
You can call an industrial hygienist to evaluate your workplace. You can also determine the levels using a dust sampling device or a light sensor that analyzes the amount of dust in the air.
The NFPA recommends using the “three C’s” if you have dust-producing operations at your business:
- Contain. Use equipment that contains the dust within the machine you’re using. Ideally, the dust created by operating the machine never escapes into the air or settles on surfaces. One example is a filtration device that pulls dust back into a container attached to the machine.
- Capture. Use another machine to capture the dust as it escapes into the air or onto surfaces. Dry dust and wet dust collector systems, downdraft tables and bin vent collectors are dust-capturing machines that pull dust out of the surrounding environment. They use fans, ducts and filters to draw dust from the environment.
- Clean. Clean dust from shelves, machines and surfaces. Remember to remove dust from inside machines according to the manufacturer’s instructions.
The NFPA also has combustible dust exposure and prevention publications for sale.
Do your research
Combustible dust might not get top billing, but don’t let that lull you into a false sense of safety.
According to OSHA, the U.S. Chemical Safety and Hazard Investigation Board (CSB) has reviewed 140 safety data sheets (SDSs) for substances that produce combustible dust. The CSB found that 41% of the SDSs didn’t have a combustible dust warning, and the remaining 59% didn’t clearly state the danger.
Combustible dust doesn’t have its own OSHA standard, but other standards reference it. For example, OSHA references dust explosions in grain handling facilities of 1910 Subpart R, Special Industries. OSHA could also cite you for general combustible dust violations under the following:
- General duty clause
- Hazard communication standard
- Respiratory protection standard
OSHA has created a Revised Combustible Dust National Emphasis Program as part of an explosive dust
awareness initiative.
Defeat the dust
Dust accumulation can pose a severe risk if the dust is combustible. Being proactive, keeping your workplace clean, understanding the materials you use in your daily operations and training your employees can help you prevent a catastrophic accident. If you need help, contact OSHA’s On-Site Consultation Program for a no-cost, confidential assessment of your operations. Don’t give dust a chance.
Contact Us
For more information about this topic, please contact our Risk Management team.
This content is for informational purposes only and not for the purpose of providing professional, financial, medical or legal advice. You should contact your licensed professional to obtain advice with respect to any particular issue or problem. Please refer to your policy contract for any specific information or questions on applicability of coverage.
Please note coverage can not be bound or a claim reported without written acknowledgment from a OneGroup Representative.
Written content in blog post: Copyright © 2024 Applied Systems, Inc. All rights reserved.
