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.