Metal halide lamps are a member of the high-intensity discharge (HID) family of lamps, Metal-halide lamps produce high light output for their size, making them a compact, powerful, and efficient light source. Since the lamp is small compared to a fluorescent or incandescent lamp of the same light level, relatively small reflective luminaires can be used to direct the light for different applications (flood lighting outdoors, or lighting for warehouses or industrial buildings).By adding rare earth metal salts to the mercury vapor lamp, improved luminous efficacy and light color is obtained. Originally created in the late 1960s for industrial use, metal-halide lamps are now available in numerous sizes and configurations for commercial and residential applications.Like most HID lamps, metal halide lamps operate under high pressure and temperature, and require special fixtures to operate safely.