HQI (Mercury Quartz Iodide) is a special type of high-intensity discharge (or HID) lamp where the light is produced using a very high voltage arc through a gas. (The "H" in "HQI" comes from "Hg" the elemental symbol for mercury) High-intensity discharge (HID) lamps include the groups of lamps commonly known as mercury vapor, metal halide, and high-pressure sodium. ... A lamp, in technical usage, is a replaceable component such as an incandescent light bulb, which is designed to produce light from electricity. ... In electrical engineering High voltage refers to a voltage which is high. ... A gas is one of the four main phases of matter (after solid and liquid, and followed by plasma), that subsequently appear as a solid material is subjected to increasingly higher temperatures. ... A chemical element, often called simply element, is a chemical substance that cannot be decomposed or transformed into other chemical substances by ordinary chemical methods. ... General Name, Symbol, Number mercury, Hg, 80 Chemical series transition metals Group, Period, Block 12, 6, d Appearance silvery white Atomic mass 200. ...

An HQI lamp consists of a protective outer glass shield surrounding two voltage rails which are inserted into each end of a smaller inner bulb containing a gas. The lamp is powered by a 'ballast' which consists of a large capacitor and transformer to enable a constant very high voltage to create the arc in the smaller inner bulb. Like all HID lamps, HQI lamps operate under high pressure and heat, and require special light fixtures for safe use. A ballast is a device used to start a gas discharge lamp, and, once the lamp is started, to limit the flow of electric current. ... A capacitor is a device that stores energy in the electric field created between a pair of conductors on which electric charges of equal magnitude, but opposite sign, have been placed. ... Three-phase pole-mounted step-down transformer. ...

HQI lamps can produce different color temperatures when manufactured with different metal halides. They are relatively efficient light sources producing a high lumen/watt ratio (approximately 6x that of incandescent bulbs). White light is commonly described by its color temperature. ... A halide is a binary compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative than the halogen, to make a fluoride, chloride, bromide, iodide, or astatide compound. ...

HQI lamps are subsets (or types) of metal halide lamps, which in turn are subsets of high-intensity discharge (HID) lamps. They should not be confused with halogen light bulbs, which are a specialized type of incandescent light bulb. Metal halide lamps are similar to mercury vapor lamps, but instead of just mercury, they also contain all metals in the halide group of the periodic table (Hence the name). ... High-intensity discharge (HID) lamps include the groups of lamps commonly known as mercury vapor, metal halide, and high-pressure sodium. ... The halogens are a chemical series. ... An incandescent light bulb and its glowing filament. ...