CTA Report, Draft 1, ISP Review - US Chemical Safety and Hazard ...

elements—dust suspension and confinement. 14 Suspended dust burns more rapidly, and confinement
allows for pressure buildup.
Fuel, ignition, oxygen, suspension, and confinement form the five sides of the dust explosion pentagon
(Figure 10). Removing either the suspension or confinement elements prevents an explosion, though a
fire may still occur.
6.3 Significance of Particle Size
Figure 10. Dust explosion pentagon.
The ease of ignition and severity of combustible dust explosions are primarily influenced by particle size
or specific surface area. 15 Finely divided particles have a large surface area, which allows them to rapidly
react with oxygen when dispersed in air and ignited. The larger the surface area, the faster the reaction,
and the larger the explosion.
14
Confinement keeps dust particles in proximity after suspension—which allows for sufficiently rapid heat transfer
to allow continued propagation. Without confinement, a propagating explosion is not possible, though a large and
very dangerous fireball may occur.
15
Specific surface area is the total surface area per unit volume or unit mass of dust.
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