|Combustible Dust: What is it and why should I care?|
Who would have thought that dust can be a cause of an explosion? Most people probably think dust is inert and a sign of laziness. In reality though, some types of dust can actually cause explosions under certain conditions – leading to injury, death and destruction.
There are different kinds of dust so it is important to recognize what type of dust is found in your facility and whether it is listed as an explosive dust by OSHA. There are agricultural, carbonaceous, metal, chemical and plastic dusts.
Some require more serious management than others. Here is a listing provided by OSHA.
How does dust cause explosions?
You may wonder how dust can cause explosions. 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 combustible 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 and lead to larger, more destructive explosions. Activated sprinkler systems may also stir up additional dust and carry the particles to other areas, thus actually spreading the threat of further explosions.
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 easily visible to you. One deadly pharmaceutical plant explosion was contributed to a build up of explosive dust above a suspended ceiling. It is important to identify the areas in you facility that dust may accumulate and hide.
NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids, also recommends:
Ruwac is here to help
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Photo acquired from www.cbs.gov.