According to information gathered by the National Electrical Manufacturers Association (
www.nema.org), there are approximately 40 million metal halide systems in North American alone, and only a very few instances of nonpassive failures have occurred.
Although it is not possible to predict, or eliminate the risk, of a metal halide lamp exploding, there are several precautions which can be taken to reduce the risk:
* Using only well designed lamps from reputable manufacturers and avoiding lamps of unknown origin.
* Inspecting lamps before installing to check for any faults such as cracks in the tube or outer bulb.
* Replacing lamps before they reach their end of life (ie. when they have been burning for the number of hours that the manufacturer has stated as the lamp's rated life).
* For continuously operating lamps, allowing a 15 minute shutdown for every 7 days of continuous operation.
* Relamp fixtures as a group. Spot relamping is not recommended.
