A UV indicator is a sensor, usually in the form of a small sticker, placed on the surface of a safety helmet. This element reacts to ultraviolet (UV) radiation, an invisible component of sunlight, which gradually degrades the structure of the plastic from which the helmet is made. The helmet material thus becomes more brittle and loses its original protective capabilities. Under the influence of sunlight, the indicator gradually changes its color, for instance, fading completely from its original red. This visible change serves as a signal that the helmet has reached the end of its service life, and it must be replaced with a new one to ensure safety.