The presence of combustible dust in industrial facilities call for the use of Class II explosion proof lighting systems. Due to the complex nature of such work sites, NFPA 654 (Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids) was created by regulators.
A report by Georgia Tech Research Institute implies that the creation of a flammable dust cloud measuring 10 feet is capable of blocking a 25-watt fixture. Examples of volatile dust include the following: titanium, magnesium, tantalum, flour, grains and more.
This standard recommends the use of Class II explosion proof fixtures to reduce the possibility of ignition. When maintaining Class II lights, the guideline suggests to periodically check the surface of lamps for the accumulation of combustible dust (A-4-2.1[g]). To facilitate effective removal of dust, explosion proof collectors and vacuums should be utilized. Explosion proof vacuums should not create or generate dust clouds, which can increase the risk of combustion.
Because high-heat surfaces can set off volatile dust, it is also critical to segregate heated surfaces from such materials. For lighting systems, features that promote cooling, such as vents or fins may help maintain adequate operating temperatures.
Defining Dust Accumulation
Criteria for the accumulation of explosive dust varies, depending on the type of material, as well as the size of particles. As a general rule, 1/32-inch dust accumulation (thickness) covering a minimum of 5 percent of the work area requires immediate cleaning. For grain elevators, the threshold is 1/8-inch dust accumulation (according to OSHA 1910.272).
Lastly, the size of dust particles should be taken into consideration in order to better understand the type of protective measures required. NFPA 654 defines flammable dust as fine, solid material that is 420 microns (or smaller) in diameter and comes with ignitable properties.…