Metal halide lighting, the type of lighting in commercial/industrial facilities, could unnecessarily increase the potential for fire and property loss, particularly if it is improperly utilized. You have undoubtedly seen these types of lights, often in large, open areas with high ceilings such as warehouses and manufacturing facilities; because they are generally more energy efficient for their wattage than other light sources.
Normally the failure of a light fixture or lamp, means that the lamp fails to illuminate when it is energized; however, on occasion, the lamp can fail violently or rupture, fracturing the arc tube and expelling hot quartz fragments, with the potential for ignition of nearby combustible materials. Major manufacturers of metal halide lighting have issued product specification literature and bulletins warning consumers of the possibility of violent failure of these lamps. Many of the manufacturers list these warnings on the product packaging itself.
The possibility of lamp failure increases significantly as it approaches and exceeds its rated life. Obviously not all failures are violent, and one manufacturer suggests that less than one violent rupture occurs in 100,000 failures, however, when you consider the number of metal halide lamps and fixtures in service, the number of potential fires is quite significant.
Some, if not most, manufacturers also produce lamps that have an internal arc tube shield, or containment barrier, of tempered or borosilicate glass. The barrier is designed to resist the rupture of the quartz arc tube and contain the hot fragments within the outer bulb. These lamps will indicate on the packaging that they are “suitable for use in open fixtures.” Lamps that do not have this internal arc tube shield, or similar means of containment, will state that they “must be operated in a suitably enclosed fixture.”
A properly installed lamp, suitable for an open fixture, can accidentally be replaced with a lamp requiring installation in an enclosed fixture. Be sure you are using the right type of lamps for your application.