The Dangers of Combustible Dust and How to Prevent Them

17Aug2015

Uniforms and Apparel

Persons who work inside industrial facilities have to be well aware of the variety of potential hazards they may encounter while on the job. There can be a number of threats present at any time, depending on the type of building and the kinds of industrial processes found inside it—radiation, noxious gases, poisonous chemicals, and much more. There is one particular threat, however, that receives too little attention—and ignorance of this phenomenon can have deadly consequences. We’re referring to combustible dust. Not only can combustible dust trigger massive explosions, it is often misjudged as an industrial hazard because this particulate matter often comes from seemingly benign sources. As we will see, though, this is not a topic that should be ignored.

Introduction to Combustible Dust

Fine airborne particles that can catch fire or explode—that is combustible dust. The particulate matter may be organic materials, metallic materials, or inorganic non-metallic materials. It’s worth keeping in mind that some types of combustible dust are composed of materials that are, under most circumstances, inert; they can catch on fire only if the particles reach a certain level of concentration. These kinds of dust can be especially hazardous precisely for that reason, as persons in the area may have good cause to believe that no danger is present.

Combustible dust can settle on a variety of surfaces—equipment, desks, floors, and more—and become airborne due to human or mechanical activity in the area. However, it can’t catch on fire without a source of ignition, such as heat or open flame. Additionally, combustion cannot occur unless oxygen is present in the air.

Types of Combustible Dust

This kind of hazardous particulate matter is more common than you probably think—it can be found across a wide range of industries, including the rubber, paper, plastics, pharmaceutical, textile, and tobacco sectors.

Any of the following materials can be combustible when in dust form:

Cotton Starch Carrots Garlic Rice flour
Parsley Milk Sugar Whey Soy flour
Charcoal Soot Corn Cork Wheat flour
Ascorbic acid Sulfur Lactose Zinc Aluminum
Bronze Epoxy resin Polyacrylamide Polypropylene Vinyl acetate

Bear in mind that this is only a partial list of combustible dust matter.

Places Where a Combustible Dust Accident Can Occur

If a given workplace environment generates dust, it is very likely to be vulnerable to a combustible dust explosion. Remember that dust isn’t merely what collects on surfaces that go extended periods without seeing use; there are, in fact, many ways to generate this type of particulate matter. Dust can be created by the cutting, crushing, polishing, grinding, shaping, recycling, or processing of certain materials.

Confined spaces are particularly susceptible to incidents with combustible dust, as explosions cannot occur unless there is an adequate concentration of “fuel” in the air.

How Explosions Happen

The Dangers of Combustible Dust and How to Prevent Them

Airborne dust can explode in the presence of a source of ignition and a sufficient amount of oxygen. Often, explosions occur when settled dust is dislodged by movement (e.g., machinery is turned on after a long hiatus) and comes into contact with heat or flame.

The destructive power of a combustible dust explosion can be attributed to the fact that, in many cases, it is really two explosions that occur in quick succession. The airborne dust that is initially ignited tends to be only a small portion of the total particulate matter in the area. When the dust cloud explodes, it dislodges the rest of the particulate material—which promptly comes into contact with the ignition source, triggering a second explosion that often surpasses the force of the first. It’s even possible for the secondary explosion to set off additional ones.

Several Case Histories

Make no mistake: Combustible dust explosions can cause massive damage. This should be made clear by examining a few well-known incidents:

  • In 1999, a Massachusetts foundry was the site of an organic dust explosion that killed three people. The explosion was eventually traced to a fire inside a shell molding machine. The conflagration rapidly grew when the flames encountered substantial amounts of resin dust deposits inside the ventilation ducts. The force of the secondary explosion knocked down walls and lifted the roof. 1
  • In 2003, six people died and 38 others were injured at a pharmaceutical plant in North Carolina due to polyethylene dust that accumulated above the facility's suspended ceilings. The explosion was large enough to damage several nearby buildings. The ignition source was never found. 1

Safety Precautions

Luckily, these types of incidents are far from inevitable. Here are a handful of tips for preventing combustible dust accidents:

  • Clear out accumulations of dust. Some simple janitorial service can quite literally be a lifesaver. Be sure to check areas where dust build-up can’t be easily seen—it may be out of sight, but it can still be ignited if a fire breaks out. It’s best to use a vacuum to remove dust, as brooms and hoses tend to leave significant amounts of particulate matter behind.
  • Remove ignition sources when possible. Remember that these explosions are commonly set off by heat and/or open flame.
  • Ensure proper ventilation. This can prevent hazardous dust clouds from forming.

The Role of Flame-Resistant Apparel

As we have seen, igniting combustible dust can cause a massive, out-of-control blaze. In a lot of cases, death and serious injury aren’t caused by the primary and secondary explosions but rather by the ensuing fire. Many people caught in these blazes have sustained severe harm due to one simple fact: They were not wearing flame-resistant clothing.

So what are the properties of this clothing that make it flame resistant? Properly designed flame-resistant apparel will not melt or split open when exposed to flame, which protects the skin of the wearer. It also will not permit flame to spread over the surface of the material. Furthermore, this type of clothing insulates the user from the effects of intense heat. These qualities add up to a substantial degree of protection from fire-related injury—the wearer is not invulnerable to harm, but is much more likely to walk away without suffering lasting effects. Accidents happen, but protective clothing can prevent them from causing disaster.

Sources

  1. https://www.osha.gov/dts/shib/shib073105.html

For more information about how to protect yourself when in reach of these dangerous chemicals