By Rick Maj, Industrial Hygienist, and Deb Bailey, Industrial Safety Consultant Specialist
When we hear the term combustible, we think of things that can burn. This is true, but what most people don’t think about is dust. Combustible dust burns and explodes! Envision dust in your house—those fluffy tumbleweed-like balls that live in the dark corners under our couches or beds, or that fine layer of dust that miraculously appears on my furniture a day after cleaning. It seems totally harmless, but in the perfect environment the results can be devastating.
Now you’re curious… right? What is the perfect environment? Well, that environment consists of five elements and is known as the Combustible Dust Pentagon.
We know that the fire triangle must have three things for a fire to occur: fuel, oxygen, and an ignition source. These are the first three sides of the pentagon. The next element is dispersed dust (which is also the fuel in our case). These particles are so small (<500 microns, or the size of granulated sugar or smaller) that they can stay suspended in air, much like the dust we see floating when the sun shines through a window.
The final element is confinement. The dust cloud needs to be confined in an area for a combustible dust event to occur. Knowing the elements of the Combustible Dust Pentagon can help you minimize the possibility of a fire.
Combustible dust is a new problem, right?
Not exactly! It has been over 13 years since the 2008 explosions at the Imperial Sugar factory in Port Wentworth, GA, that claimed 14 lives, injured 38 people, and led to the Occupational Safety and Health Administration (OSHA) issuing fines of nearly $9 million. That may seem like a long time ago, but did you know that the first recorded dust explosion occurred at a bakery in Turin, Italy on December 14, 1785? Following a series of grain dust explosions during the 1980’s, OSHA issued a dust standard for the grain industry, 29 CFR 1910.272 (1987).
There is no OSHA combustible dust standard for general industry, but the National Fire Protection Association (NFPA) has multiple codes governing dust hazards. The NFPA Standards cover everything from design, mitigation, and installation, to recommended practices. They cover all phases of manufacturing, blending, conveying, and handling combustible dust.
How do I know if my dust is a combustible dust?
It would be great if all the dust in world came pre-labeled. The dust particles would wear little warning signs like “Caution: Explosible Dust” or “Combustible Dust: Keep Away from Ignition Sources.” Since that doesn’t happen, we must rely on other resources. The first option is to check the Safety Data Sheet. A second way is to check with the manufacturer. Or a third method is to review published data.
If you can’t find information on your particular dust, then you need to test it. So, what kind of test do you run? The first step in testing would be an Explosibility Screening Test (Go/No-Go test), which determines if your dust presents a combustible dust hazard. A positive test provides a good starting point, which can assist you in your next step of the combustible dust journey, a Dust Hazard Analysis (DHA).
What should I do about the dust?
Unfortunately, one of the most frequent actions we see for handling combustible dust is people taking no action. Even one simple step can help.
Housekeeping is the easiest and cheapest control method you can implement. Develop a plan for frequent and proper cleaning in areas where there is visible accumulation of combustible dust. The buildup of even a very small amount of dust can cause serious damage from secondary explosions.
Effective evaluation and management of combustible dust according to NFPA 652 requires the following:
- Determining the combustibility of your dust
- Assessing any fire, flash fire, and explosion hazards (DHA)
- Managing the fire, flash fire, and explosion hazards through mitigation:
- Detection and ignition control systems
- Explosion venting
- Explosion suppression
- Explosion isolation
- Establishing a safety management system for processes where a fire or explosion may occur
- Communicating the hazards to affected personnel
So, do you have combustible dust in your facility? Essentially, any workplace that generates dust is potentially at risk, but the good news is combustible dust explosions are preventable. When you take these steps to understand, evaluate, and control your combustible dust hazards, you can protect your people and facility.
Our experts can assist employers with understanding, recognizing, and preventing combustible dust hazards. Request a safety consultation online or call 1-800-644-6292, and we’ll get you in touch with one of our specialists. Or view our webinar replay on combustible dust: Combustible Dust Hazard Analysis: What is It & How Can You Prepare for It? (Webinar Recording Replay) (bwclearningcenter.com). If you don’t already have an account for the BWC Learning Center, view instructions to create one here.
Additional Resources:
- US Chemical Safety & Hazard Investigation Board
- Occupational Safety & Health Administration
- Combustible Dust: An Explosion Hazard – Overview | Occupational Safety and Health Administration (osha.gov)
- Federal OSHA issues third largest fine in history following sugar refinery explosion | Occupational Safety and Health Administration
- National Fire Protection Association
BWC Blog 