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Januar y 2019

What You Need to Know

About Combustible Dust

By Steve Ochs, Casella U.S. tible dust incidents between 1980 and 2005 killed 119
Businesses dealing with powders and other small-
B industrial facilities.” Figure 1 gives further historical
workers, injured 718 others, and extensively damaged
particle materials at the center of their operations
are, by nature, no stranger to airborne dust. While the
2
perspective on global dust explosions.
respiratory risks posed by dust inhalation are often
accounted for with personal protection equipment, a
more immediate danger can sometimes be overlooked:
the possibility of dust-derived explosions. It is not only
facilities with obviously combustible materials, such as
coal dust, that are at risk. Any workplace that gener-
ates dust is potentially vulnerable.
With proper controls, combustible dust explosions
and fires are preventable. As a result, it’s important to
know how to detect dangerous dust levels and mitigate
the risks they pose to ensure worker and bystander
safety. This article will lay out answers to frequently
asked questions (FAQ) about combustible dust to help
you know how to identify risks, comply with standards
and create a safer environment.
Figure 1: Number of dust explosions
1. Where Does Combustible Dust Come
From? 3. What Causes a Combustible Dust
Combustible dust is created when materials are trans- Explosion?
ported, handled, processed, polished, ground, and
A dust explosion can only occur when the following
shaped. Dust is also created by abrasive blasting, cut-
five factors are present:
ting, crushing, mixing, sifting, or screening dry materi-
• Fuel (in the form of combustible dust particles)
als, as well as during processing of wet materials that
• Dispersion of the fuel (in the form of a dust cloud)
causes build-up of dried residue. We see combustible
• Oxygen (in the form of air)
dust often in production and processing environments
• Confinement of the cloud (in the form of a closed
related to:
area)
• Agriculture (e.g. grain elevators, bins, silos)
• An ignition source (in the form of a spark or open
• Chemicals (e.g. fertilizer)
flame)
• Food (e.g. candy, sugar, spice, starch, flour, feed)
Dust dispersion can be caused by processing (e.g. a
• Metal powder processing or storage (especially
dry filter being pulse cleaned) or as an after effect of a
magnesium and aluminum)
primary explosion’s blast wave that distributes dust be-
• Paper
fore igniting it in a secondary explosion.
• Pharmaceuticals
In Figure 2, you can see how this occurs. A sec-
• Plastics
ondary explosion can be far more damaging than a
• Rubber (e.g. tire manufacturing)
primary explosion due to the area covered by ignited
• Textiles
combustible dust.
• Tobacco
• Woodworking (e.g. furniture manufacturing)

2. How Dangerous Is Combustible Dust?

Dust explosions continue to be a persistent prob-
lem for many industries, and even highly trained
individuals such as enforcement officials, insurance
underwriters, and company safety professionals of-
ten lack awareness of combustible dust hazards. A
single metal dust explosion that occurred in Jiangsu
Province, China, killed 75 people and injured an-
other 185. According to the U.S. Chemical Safety Figure 2: The role of combustible dust in secondary explosions
1
and Hazard Investigation Board (CSB), “281 combus- (courtesy of OSHA)