What is the Dust Pentagon?

The 5 Elements of a Dust Explosion

There are five required elements for a dust explosion. They are sometimes referred to as the Dust Explosion Pentagon:

dust collector fire pentagon

  • A fuel, which is the combustible dust
  • An oxidant, which is typically the oxygen in the air
  • An ignition source capable of igniting materials when they are dispersed as a cloud
  • Dispersion, which is when the accumulated dust is spread out and creates a dust cloud
  • Confinement, which leads to pressure rise and a potential vessel rupture, facility obstruction or structural collapse

Deflagration

A term often used in connection with dust fires and explosions is ‘deflagration’ and is defined as combustion which propagates through a gas or across the surface of an explosive at subsonic speeds, driven by the transfer of heat. The term is used for both flash fires and explosions. With a dispersed dust cloud, deflagration can cause an unconfined flash fire or, when confined, an explosion that ruptures the containment vessel.

The Two Explosions

Combustible dust explosions often involve two explosions: primary and secondary. The primary explosion is the first to occur when dust suspension in a confined space is ignited and explodes. The first explosion will dislodge other dust that has accumulated which, when airborne, also ignites. A secondary dust explosion is often more destructive than the primary one.

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