1.Oxygen – Air is the most common oxidizing medium. O2 must be present in sufficient concentration to support the combustion.
2. Ignition – Ignition source is often the only leg of the pentagon not readily present. Possible ignition sources include open flame, hot surfaces, static or electrical discharges, and heat from friction or mechanical impact.
3. Dispersion – A suspended cloud of explosive dust with sufficient concentration will allow combustion to occur more rapidly than in a layer.
Dust Explosions occur when all five of the legs of the Dust Explosion Pentagon are present.
4. Confinement – A suspended dust cloud must be enclosed in order to build pressure that is characteristic of a dust explosion. Without confinement, the rapid combustion is a Flash Fire.
5. Fuel – Combustible Dusts serve as fuel for combustion. Examples include grain dust, plastics, cornstarch, coal, wood dust, and metals.
Dust Explosion Mitigation Techniques
NFPA 652, Standard on the Fundamentals of Combustible Dust (2019), requires that facilities and processes are designed to mitigate the dangerous consequences of fires and explosions that are a hazard of handling combustible dust. To meet this requirement, facilities can elect to utilize either a Prescriptive approach or a Performance-Based approach. Using a Performance-Based approach involves the design of a system or facility that is assessed and evaluated against specific design criteria to demonstrate safety against
each identified Fire and Explosion Scenario relevant to the system. The system must be able to adequately address the areas of Life Safety, Structural Integrity, Mission Continuity, Mitigation of Fire Spread and Explosions, and the Effects of Explosions. When utilizing a Performance-Based design, the proposed system or facility must be tested using appropriate methods and calculations acceptable to the Authority Having Jurisdiction (AHJ).
