Abstract: A method is provided for activating a photocatalytically active, for example titanium-dioxide-containing, outer layer deposited on a composite, by means of at least one element generating a radiation, for example for generating ultraviolet radiation. The method may include: forming the at least one radiation-generating first element within the composite; forming at least one sensor within the composite; recording an actual value of a physical variable characterizing luminous radiation by means of the at least one sensor, wherein the luminous radiation is emitted by a light-generating second element; comparing the recorded actual value with a first threshold value within an evaluation device; and switching on the at least one radiation-generating first element if the actual value is below or above the first threshold value.