Tritium Exit Signs - How do they work? Self Luminous Tritium Exit signs do not require electricity or batteries for illumination. Because they don't require electric wiring, they are being 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 building owners specify self-luminous signs: It saves them money while providing safe and reliable exit location identification. All self-luminous signs work on the same principle. They are powered by tritium gas, a low-level isotope of hydrogen. What Is Tritium?
Tritium gas, an isotope of the chemical element hydrogen, contains one proton, two neutrons and is naturally present in the atmosphere. Light hydrogen or protium is a hydrogen isotope with one proton and no neutrons. If we were to add one neutron, the result would be a heavy hydrogen isotope called deuterium. Adding a second neutron would result in the creation of the isotope tritium. When isotopes are stable, they retain their molecular structure indefinitely. However, certain isotopes are subject to decay and are, therefore unstable in nature. Unstable isotopes are referred to as radioactive isotopes. In radioactive isotopes, the nucleus, or center, decays to form a different nucleus and a nuclear particle. The nucleus in tritium decays by emitting an electron called a beta particle. The rate at which a radioactive element looses its radioactivity (decays) determines its half-life the time it takes the element to decay to half its original activity level. Tritium has a half life of approximately 12 ½ years which is very short compared with many isotopes you may have read about in articles on current events or in high school or college science courses.
How Do Tritium Exit Signs Work?
Self-luminous exit signs use the electron from the tritium to provide illumination without the need for a source of electrical power. The process is very similar to that in your television set picture tube where an electron is used to illuminate the front screen of the tube. The electron from tritium however has only about ¼ of the energy of the electron in a color TV picture tube. That is why self-luminous exit signs are not visible in daylight while TV pictures are. Actually, the tritium electron from the tritium has such a low energy that it cannot even penetrate an ordinary sheet of paper. Because of this very low energy level, tritium is one of the safest and most benign of all radioactive materials and is therefore approved by the Federal Authorities for use in self-luminous exit signs in commercial buildings as well as all commercial aircraft. To produce the illumination, the tritium gas is contained within a hermetically sealed glass tube. The inside surfaces of the tube are coated with a phosphor (A) just like the inside surface of a television picture tube. Electrons emitted by the tritium (B) bombard the phosphor causing it to produce illumination.
Is the Exit Sign Bright Enough?
When the normal lighting is on in a building, you will not see the tritium lamps. However, the UL required contrast ratio of the face colors makes the exit sign very visible. When the power has gone out, the sign becomes very visible. The brightness of a tritium exit sign is more than twice the Underwriters Laboratories (UL) minimum requirement.
Are Self Luminous Exit Signs Approved?
Our self-Luminous Tritium Exit Signs meet the requirements of the National Fire Protection Association (NFPA) Life Safety Code 101. NFPA 101 is the most comprehensive code addressing safety to life from fire and similar emergencies in both new and existing buildings. NFPA has been adopted statewide in 33 states. Click here for more information. Other approvals include UL, OSHA, NSI, BOCA, ICBO, SBCCI and the FAA.
What If A Tube Breaks?
Self-luminous signs contain a number of individual tritium filled tubes contained within a protective case. The tubes in signs are shock-mounted inside a high-impact plastic case designed to be tamper and vandal resistant. A clear high-impact plastic shield across the face of the sign provides additional protection and serves as another barrier against accidental damage. To meet the regulations of the U.S. Nuclear Regulatory Commission, signs are extensively tested to ensure that, when properly installed they will not fail under normal usage conditions. If the protective shield and case are penetrated and a Tube should break, releasing the tritium gas, there is no hazard. Because it is hydrogen and therefore lighter than air, when released, the tritium gas is dispersed rapidly and harmlessly into the atmosphere to join the naturally occurring tritium already dispersed. In the highly improbable event that all of the multiple tubes should fracture, the effect is still less than half of that received from naturally occurring radioactive sources during a year, and is similar to the difference between living at sea level and moving to an elevation of 5,000 feet. The chart below compares the unlikely complete release of all tritium gas in a self-luminous exit sign to some familiar comparisons we encounter in our daily lives.
How do I dispose of the sign after it has reached it's life span?
The manufacturer will dispose of your tritium exit sign after it has expired. They will process all necessary paperwork and assure that the product is recycled and reclaimed. They will not dump or store expired signs in landfills or other storage sites. For more information contact us at 877-305-0898 or email sales@theexitstore.com.
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