The difference between xenon and halogen lights is the gas used in the light bulb. Xenon lamps use xenon gas, while halogen lamps use a gas from the halogen group. Iodine and bromine are the most common halogens used in lamps.
Iodine is used in halogen lamps in its elemental form; bromine is used as part of a hydrocarbon compound. While bromine and iodine are the preferred halogens for lamps, it is also possible to use chlorine and fluorine. These are less popular because bromine and iodine are more efficient and less reactive with the other components of the bulb. Halogen lamps often use krypton or xenon in combination with halogen gases, but the resulting light is not referred to as a xenon lamp.
Xenon lights work by passing electricity through high-pressure, ionized xenon gas. Unlike halogen lamps, which combine a halogen with a noble gas, xenon is the only gas component in these lights. Some xenon lamps utilize liquid mercury to generate higher levels of ultraviolet light.
Halogen bulbs are safe to dispose of; unlike xenon-mercury or compact fluorescent bulbs, they do not contain mercury. Xenon lights that do not contain mercury are also safe to dispose of normally. Xenon-mercury bulbs are classified as hazardous waste due to their mercury content and must be disposed of in accordance with local regulations.