Halogen, bulbs, lamps, light bulbs, lights, lighting problems, lighting service, replace bulbs, lighting information, electrical service, Delaware County, Delco, electrician, electrical contractor, Philadelphia, PA Philly Main Line, Lower Merion, Philadelphia, PA.  A halogen lamp is an incandescent lamp in which a tungsten filament is sealed into a compact transparent envelope filled with an inert gas and a small amount of halogen such as iodine or bromine. The combination of the halogen gas and the tungsten filament produces a chemical reaction known as a halogen cycle that increases the lifetime of the bulb and prevents its darkening by redepositing tungsten from the inside of the bulb back onto the filament. The halogen lamp can operate its filament at a higher temperature than a standard gas filled lamp of similar power without loss of operating life and because of their smaller size, halogen lamps can be used with optical systems that are more efficient.