Quality light in a hazardous location is necessary, but it could also be dangerous. Knowing the facilities, and the compositions that can be found in the location allows a proper, and safer work environment. Several episodes of explosive dust have been reported and affected industries throughout the world, some of which have caused huge losses. Any gas explosion is the result of the presence of flammable gas, the presence of oxygen, a mixture of the last two and an ignition source. Explosions usually take place inside of the equipment (primary explosion), but the most severe consequences are usually caused by explosions outside of the equipment (secondary explosion). Dust explosions almost always lead to serious financial losses, injuries, and fatalities.
Some of the materials that can cause dust explosions are grain, wood, linen, sugar, synthetic, plastics, organic pigments, pesticides, pharmaceuticals, coal and peat, and metals (aluminum, magnesium, titanium, zinc, iron, etc.). Some of these materials are not flammable but they can burn or explode if the particles are the right size and in the right concentration.
According to the agencies that regulate lighting in hazardous environments the Class designation describes the type of materials that may be present, including gas, liquid produced vapors, dust, and fibers. Class I present natural gas, petroleum, and chemical while Class II locations contain combustible dusts, such as starches, flour, and wood flour. The category of Division defines the probability that those materials will be present to form flammable or combustible fuel-air mixtures.
Fixtures placed within the UL classification must ensure that ignition is never allowed into the environment; explosion-proof fixtures feature “flame-paths” that allow the gases to escape to the outside atmosphere only after the gas has traveled and cooled within the fixture. The maximum temperature of the exposed surface of these fixtures is a determinant factor for them to be able to disarm inside themselves; they are classified as flameproof, explosion-proof (T- rating on the exterior of the fixture), enclosed and gasketed (T-rating on the inside of the fixture) and restricted breathing (T-rating on the surface of the fixture).