HID (high-intensity discharge) lamp is a type of electrical bulb which produces light by means of an electric arc between tungsten electrodes housed inside a translucent arc tube. This tube is filled with both gas and metal salts. The gas facilitates the arc’s initial strike via a high voltage pulse produced by the igniter. Once the arc is started, the ballast maintains a constant arc which evaporates the metal salts forming a plasma. This greatly increases the intensity of light produced by the arc and reduces its power consumption.
HID requires three components: a bulb, an igniter and a ballast. Instead of a filament, HID is a xenon gas filled bulb with 2 electrodes. Applying a high voltage 20,000 volt pulse (via the igniter) a plasma arc is formed across the two electrodes in the bulb. Once ignited, the ballast takes over, keeping the bulb running at a constant temperature. HID lights take approximately 15 to 25 seconds to reach a stable brightness, a fact not all buyers know.