Metal halide is a type of high-intensity discharge (HID) gas discharge lamp.
Metal-halide lamps have a high-luminous efficiency of around 75 - 100 lumens per watt, about 2-3 times the efficiency of mercury vapor or fluorescent lights and a similar efficiency to LED lighting, they have a moderately long bulb life (6,000 to 15,000 hours) and produce an intense white light.
Metal-halide lamps are used for both general lighting purposes indoors and outdoors, often for automotive and specialty applications. Because of their wide spectrum, they are used for indoor growing applications, in athletic facilities and are quite popular with reef aquarists, who need a high intensity light source for their corals.
Metal-halide lamps are used in automobile headlights, where they are commonly known as "xenon headlamps" due to the use of xenon gas in the bulb instead of the argon typically used in other halide lamps. They produce a more intense light than incandescent headlights.
However, Halide bulbs require electrical ballasts to limit the arc's current - otherwise the bulb destroys itself.
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