Definition - What does Combustible Dust mean?
A combustible dust is any dust (fine material) that has the potential to catch fire and explode when mixed with air.
A material that is not combustible or flammable under many circumstances can potentially act as a combustible dust if it is present as a fine particle and mixed with air in a particular concentration. As such, most solid organic materials (sugar, flour, wood, grains, etc.) can form combustible dusts, as can many metals and some inorganic compounds.
Safeopedia explains Combustible Dust
Combustible dust explosions are often characterized by rapid total ignition and consumption of the whole quantity of flammable dust products. This produces extreme air pressure that can blow out walls and destroy structures.
According to the U.S. Chemical Safety Board (CSB), 281 dust-related incidents in the United States killed 119 workers and injured 718 workers between 1980 and 2005. The risk of an explosion or fire due to combustible dust is often unknown or underappreciated in workplaces where combustible dust incidents occur. A common cause of combustible dust incidents is improper cleanup of dust due to poor workplace housekeeping. A relatively small amount of dust can pose a significant hazard.
The National Fire Protection Association has released a comprehensive combustible dust standard that recommends workplaces conduct a dust hazard analysis. Thus far, OSHA does not have a mandatory combustible dust standard for general industry. The CSB has labelled the need for a standard as the first issue in its “Most Wanted Chemical Safety Improvement” program.