Tritium Exit Signs are Self Powered and are the most reliable exit signs produced today. Self Powered Tritium Exit Signs require no external power source, no electrical wiring or batteries to replace and are always ready to provide an effective, maintenance-free exit system. Self Powered Tritium Exit Signs will provide a luminescent sign under any condition, even during an extended period of power outage. Tritium, also known as 3H or H-3, is a form of hydrogen. In EXIT signs, tritium gas is contained in sealed glass tubes lined with a light-emitting compound. The tritium gives off low-energy beta radiation that causes the lining to glow. This type of radiation cannot penetrate a sheet of paper or clothing. Tritium Exit signs have many useful purposes in a variety of facilities: churches, schools, offices, movie theaters and warehouses to name a few. Tritium Exit Signs serve an important safety function by marking exits to be used during power outages and emergencies. The signs pose little or no threat to public health and safety or security. If inhaled, Tritium leaves the body relatively quickly. Tritium gas is odorless, colorless and tasteless, and is lighter than air. There are several ways to know whether an EXIT sign contains tritium: when the lights or power are off, tritium will make the word EXIT glow green or red. Tritium Exit Signs must also have a permanent warning label that mentions tritium, 3H or H-3; displays the three-bladed radiation warning symbol; and states "Caution-Radioactive Materials." Tritium Exit Signs will also have a serial number and an expiration date. If all four letters in EXIT are fully lit, the sign is working properly. If not, the sign may be damaged or have reached the end of its working life.