This is the general term for a mercury vapor, metal halide, or high-pressure sodium lamp. They differ from incandescent lamps in that there is no filament, but contain gas which when exposed to an electric charge, produces light. HID lamps require a ballast, which controls the electrical current that flows into the lamp.
Lamps in which an arc passing between two electrodes in a pressurized tube causes various metallic additives to vaporize and release large amounts of light. All HID lamps, High Pressure Sodium · Low Pressure Sodium · Mercury Vapor · Metal Halide, offer outstanding energy efficiency and service life. Metal halide lamps also offer good to excellent color rendering index (CRI).
A lamp that produces light when electricity excites different gases within a pressurized glass envelope. HID lamps include mercury vapor, metal halide and high-pressure sodium types. See also Ballasts.