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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Dust explosion | 2/2 | https://en.wikipedia.org/wiki/Dust_explosion | reference | science, encyclopedia | 2026-05-05T10:47:24.448574+00:00 | kb-cron |
electrostatic discharge (e.g. an improperly installed conveyor belt, which can act like a Van de Graaff generator) friction electrical arcing from machinery or other equipment hot surfaces (e.g. overheated bearings) fire self-ignition However, it is often difficult to determine the exact source of ignition when investigating after an explosion. When a source cannot be found, ignition will often be attributed to static electricity. Static charges can be generated by external sources, or can be internally generated by friction at the surfaces of particles themselves as they collide or move past one another.
== Mechanism ==
Dust has a very large surface area compared to its mass. Since burning can only occur at the surface of a solid or liquid, where it can react with oxygen, this causes dust to be much more flammable than bulk materials. For example, a 1 kg (2.2 lb) sphere of a combustible material with a density of 1 g/cm3 would be about 12.4 cm (4.9 in) in diameter, and have a surface area of 0.048 m2 (0.52 sq ft). However, if it were broken up into spherical dust particles 50 μm in diametre (about the size of flour particles) it would have a surface area of 120 m2 (1,300 sq ft). This greatly-increased surface area allows the material to burn much faster, and the extremely small mass of each particle allows them to catch on fire with much less energy than the bulk material, as there is no heat loss to conduction within the material. When this mixture of fuel and air is ignited, especially in a confined space such as a warehouse or silo, a significant increase in pressure is created, often more than sufficient to demolish the structure. Even materials that are traditionally thought of as nonflammable (such as aluminium), or slow burning (such as wood), can produce a powerful explosion when finely divided, and can be ignited by even a small spark.
== Effects == A dust explosion can cause major damage to structures, equipment, and personnel from violent overpressure or shockwave effects. Flying objects and debris can cause further damage. Intense radiant heat from a fireball can ignite the surroundings, or cause severe skin burns in unprotected persons. In a tightly enclosed space, the sudden depletion of oxygen can cause asphyxiation. Where the dust is carbon based (such as in a coal mine), incomplete combustion may cause large amounts of carbon monoxide (the miners' after-damp) to be created. This can cause more deaths than the original explosion as well as hindering rescue attempts.
== Protection and mitigation ==
Much research has been carried out in Europe and elsewhere to understand how to control these dangers, but dust explosions still occur. The alternatives for making processes and plants safer depend on the industry. In the coal mining industry, a methane explosion can initiate a coal dust explosion, which can then engulf an entire mine pit. As a precaution, incombustible stone dust may be spread along mine roadways, or stored in trays hanging from the roof, to dilute the coal dust stirred up by a shockwave to the point where it cannot burn. Mines may also be sprayed with water to inhibit ignition. Some industries exclude oxygen from dust-raising processes, a precaution known as "inerting". Typically this uses nitrogen, carbon dioxide, or argon, which are incombustible gases which can displace oxygen. The same method is also used in large storage tanks where flammable vapors can accumulate. However, use of oxygen-free gases brings a risk of asphyxiation of the workers. Workers who need illumination in enclosed spaces where a dust explosion is a high risk often use lamps designed for underwater divers, as they have no risk of producing an open spark due to their sealed waterproof design. Good housekeeping practices, such as eliminating build-up of combustible dust deposits with a dust collector, also help mitigate the problem. Best engineering control measures which can be found in the National Fire Protection Association (NFPA) Combustible Dust Standards include:
Wetting Oxidant concentration reduction Deflagration venting Deflagration pressure containment Deflagration suppression Deflagration venting through a dust retention and flame-arresting device
== Notable incidents == Dust clouds are a common source of explosions, causing an estimated 2,000 explosions annually in Europe. The table lists notable incidents worldwide.
== See also == Air to fuel ratio Power tool
== References ==
== External links ==
Incidents in France and the US:
Combustible dust explosion investigation products from the Chemical Safety Board Combustible Dust Policy Institute-ATEX OSHA case studies of dust explosions Protecting process plant, grain handling facilities, etc. from the risk of dust hazard explosions:
Hazard Monitoring Equipment – Selection, Installation and Maintenance Seminars for Combustible Dust Safety HSE (UK) advice on safe handling of combustible dust Combustible Dust, CCOHS