All electrical equipment certified for hazardous locations can either be certified as explosion-proof or intrinsically safe. The objective is similar, it is designed to avoid igniting the flammable materials. However, the approach is different. Explosion-proof lights are conceived to resist an ignition of the flammable material that happens inside the light itself, whereas intrinsically safe luminaires are conceived to avoid any spark that could ignite the flammable material, to low current.
Industrial lighting must often provide illumination in areas where usual lighting is inadequate. Some factors related to the very nature of the activities carried out have to be taken into account, due mainly to the materials handled and the by-products produced. Whether the manufacturing process deals with the processing of hazardous petrochemicals or relatively benign food products such as food grain, there is always the underlying risk of accidental ignitions of flammable or explosive of materials. An atmosphere saturated with gasoline or solvent vapours can literally turn an enclosed area into a potential bomb capable of releasing enough force to destroy the entire building.
Explosion proof fixtures provide protection by preventing any ignitions within the fixture from igniting the atmosphere outside of the fixture. Explosion proof luminaires are not fully sealed, but they have the ability to prevent the ignition of the atmosphere outside the light fixture should it contain flammable vapors, gases, or combustible dusts, whereas in a standard light fixture, the bulb, contacts, wiring, and any switches are all directly exposed to the local atmosphere. The spark from a loose contact or the movement of the switch and even the heat of the bulb can be a danger.