High-intensity discharge lamps (
HID lamps) are a type of
electrical gas-discharge lamp which produces light by means of an electric arc between
tungsten electrodes housed inside a translucent or transparent
fused quartz or fused
alumina arc tube. This tube is filled with both
gas and
metal salts. The gas facilitates the arc's initial strike. Once the arc is started, it heats and evaporates the metal salts forming
plasma, which greatly increases the intensity of light produced by the arc and reduces its power consumption. High-intensity discharge lamps are a type of
arc lamp.