Tritium Exit signs or Self Luminous do not require electricity or batteries for illumination. Because they don't require electric wiring, they are installed in greater numbers in public and private buildings. A self-luminous sign remains lighted continuously, though you won't detect any illumination during daylight hours or in brightly lit rooms. In addition, self-luminous signs will maintain their illumination day in, day out, for up to twenty years. This no-cost, maintenance-free operation is why many property owners specify self-luminous signs: It saves money while providing safe and reliable exit location identification. All self-luminous signs work on the same principle as Tritium Exit signs.