Safety Insight: Dust Hazards 101: What Makes a Dust Explosible?
For a dust cloud explosion there must be an oxidant (O2 in air for example), an ignition source (flame, spark, or high heat), and a fuel (fine dust particulates); these are the familiar “Fire Triangle.” In addition, the dust must be in suspension in sufficient quantity and concentration, and confinement (limited venting) is needed. These five elements create the “explosion pentagon.” An initial explosion or primary explosion in processing equipment or in an area where accumulated dust can build up can cause a secondary explosion when additional dust is dispersed in the air. Secondary explosions can be more destructive than primary explosions.
Not all powders or dust are explosible. While aluminum dust can be very explosible, nickel powder is not, which is one reason all powders should be tested for explosibility and sensitivity to ignition from electrostatic and thermal sources of ignition.