Industries at Risk
Combustible dust explosion hazards exist in a
variety of industries, including: agriculture,
chemicals, food (e.g., candy, sugar, spice, starch,
flour, feed), grain, fertilizer, tobacco, plastics,
wood, forest, paper, pulp, rubber, furniture, tex-
tiles, pesticides, pharmaceuticals, tire and rub-
ber manufacturing, dyes, coal, metal processing
(e.g., aluminum, chromium, iron, magnesium,
and zinc), recycling operations, and fossil fuel
power generation (coal).
Prevention of Dust Explosions
To identify factors that may contribute to a
explosion, OSHA recommends a thorough
hazard assessment of:
• All materials handled;
• All operations conducted, including by-
products;
• All spaces (including hidden ones); and
• All potential ignition sources.
How Dust Explosions Occur
In addition to the familiar fire triangle of oxygen,
heat, and fuel (the dust), dispersion of dust par-
ticles in sufficient quantity and concentration
can cause rapid combustion known as a defla-
gration. If the event is confined by an enclosure
such as a building, room, vessel, or process
equipment, the resulting pressure rise may
cause an explosion. These five factors (oxygen,
heat, fuel, dispersion, and confinement) are
known as the “Dust Explosion Pentagonâ€. If one
element of the pentagon is missing, an explo-
sion cannot occur.
Catastrophic Secondary Explosions
An initial (primary) explosion in processing
equipment or in an area where fugitive dust has
accumulated may dislodge more accumulated
dust into the air, or damage a containment sys-
tem (such as a duct, vessel, or collector). As a
result, if ignited, the additional dust dispersed
into the air may cause one or more secondary
explosions. These can be far more destructive
than a primary explosion due to the increased
quantity and concentration of dispersed com-
bustible dust. Many deaths in past accidents, as
well as other damage, have been caused by sec-
ondary explosions.
FactSheet
HazardAlert: Combustible Dust Explosions
Combustible dusts are fine particle