The same as classic incandescent lamps, halogen lamps are radiators of temperature. However, by contrast, halogen lamps do not show the typical bulb blackening that incandescent lamps do. The reason for this is the halogen cycle, due to which the bulb remains clear throughout the entire service life of the bulb. Therefore, the halogen lamp always emits a constant light flux, achieving a longer service life than the classic incandescent lamp. To do this, traces of halogens are required in the filling gas of the halogen lamp.