Each type of high intensity discharge light offers certain advantages and disadvantages over other high intensity discharge lights. Some of the most widely used types of high intensity discharge lights include metal halide lights, high-pressure sodium lights and mercury vapor lights, according to Offroaders.com. Each type of high intensity discharge light operates under slightly different technologies.
The measurement "lumens" is utilized to gauge the intensity of light output from a given light source. All high intensity discharge lights are capable of emitting a considerable amount of visible light. Metal halide lights are capable of producing around 58 lumens per watt, according to DarkSkySociety.org. High-pressure sodium lights typically produce around 87 lumens per watt.
There is a somewhat dramatic difference in lifespans among the different types of high intensity discharge lights. According to ACF Greenhouses, metal halide lights have a rated lifespan up to 10,000 hours before their replacement is recommended. High-pressure sodium lights typically last longer than any other type of high intensity discharge light; they can last up to 18,000 hours. Mercury vapor lights generally last for the same number of hours as metal halide lights.
Elemental mercury is utilized in the construction of all high intensity discharge lights. According to the U.S. Environmental Protection Agency (EPA), overexposure to the elemental mercury found in high intensity discharge lights can result in respiratory failure and death. Metal halide lights can contain around 38 mg of toxic elemental mercury, according to DarkSkySociety.org. A high-pressure sodium light can contain around 15 mg of elemental mercury.
Another component that is essential to the proper function of any high intensity discharge lights is a ballast. Ballasts are used to provide a starting voltage for high intensity discharge lights, according to the sources at Arcadian Lighting. Ballasts are also employed to provide a steady, uninterrupted flow of power to the light.