Most people probably think dust is inert and a sign of laziness. In reality though, that is far from the case. So what is combustible dust and why should you care? For starters, combustible dusts can actually cause explosions under certain conditions, leading to expensive OSHA fines, destruction, injury and in the worst cases of all, death.
Which are some examples of combustible dust?
There are several different kinds of dust, so it is important to recognize what type of dust is found in your facility and whether or not it has been listed by OSHA as a combustible dust danger. Some dusts require more serious management than others. Examples of prevalent combustible dusts in the workspace include:
- Flour and grain dust
- Wood dust
- Plastic dust
For a complete listing of materials, OSHA has provided one which can be found here.
How does dust cause explosions?
You may be wondering exactly how dust can lead to a dangerous explosion. For a fire to start there must be three elements: Oxygen, heat and fuel. A simple spark in a confined area like a building, room, vessel or process equipment where explosive dust particles are dispersed in sufficient quantity and concentration can lead to rapid combustion. “These five factors (oxygen, heat, fuel, dispersion, and confinement) are known as the ‘Dust Explosion Pentagon.’ If one element of the pentagon is missing, an explosion cannot occur.” – OSHA Fact Sheet, March, 2008.
An initial explosion may dislodge additional dust particulates and lead to larger, more destructive explosions. Activated sprinkler systems may also stir up additional dust and carry the particles to other areas, thus spreading the threat of further explosions even further throughout the facility.
How much dust is too much?
This is a tough question to answer and currently being considered by OSHA. Currently they state, “The amount of dust accumulation necessary to cause an explosive concentration can vary greatly. This is because there are so many variables – the particle size of the dust, the method of dispersion, ventilation system modes, air currents, physical barriers and the volume of the area in which the dust cloud exists or may exist. As a result, simple rules of thumb regarding accumulation (such as writing in the dust or visibility in a dust cloud) can be subjective and misleading. The hazard analysis should be tailored to the specific circumstances in each facility and the full range of variables affecting the hazard.” – OSHA. (July 31, 2005). Combustible dust in industry: preventing and mitigating the effects of fire and explosions.
It’s hiding from you
Some of the explosive dust located in your facility may not be so obvious to spot by the naked eye. One deadly pharmaceutical plant explosion was contributed to a build-up of combustible dust above a suspended ceiling. This is why it is important to identify the areas in you facility that dust particles may be hiding and accumulating without your knowledge.
NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids, also recommends:
- Minimize the escape of dust from process equipment or ventilation systems;
- Use dust collection systems and filters
- Utilize surfaces that minimize dust accumulation and facilitate cleaning
- Provide access to all hidden areas to permit inspection
- Inspect for dust residues in open and hidden areas, at regular intervals
- Clean dust residues at regular intervals
- Use cleaning methods that do not generate dust clouds, if ignition sources are present
- Only use vacuum cleaners approved for dust collection
- Locate relief valves away from dust hazard areas
- Develop and implement a hazardous dust inspection, testing, housekeeping, and control program (preferably in writing with established frequency and methods.)
These main talking points are here to help you to better understand what combustible dust is and why you should care about understanding its complexities. As always, our professional experience and insight is available to provide you with further awareness on the issue, with the ultimate goal being to keep your work place safe from the dangers of combustible dust. For a free copy of our exclusive Combustible Dust Housekeeping Guide (which further explains what combustible is, why and how to clean it) you can request one here!