Tritium Exit Signs are an alternate to standard "Hard-Wired" Exit Signs. Learn about the the energy sources behind Tritium Exit Signs and the reuirements to purchase them.
General Concepts of Tritium Exit Signs
Self luminous tritium exit signs are illuminated via the radioluminescence of the phosphor coating of a glass tube by electrons emitted from a tritium gas. Basically the electrons of the phosphor coating are excited into emitting electromagnetic radiation in the visible spectrum (i.e. light). This illumination is internal, without the need for a source of electrical power, therefore these tritium exit signs are also known as "self luminous exit signs"" or "self luminous tritium exit signs.",
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 1/4 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. The electron from the tritium gas has such low energy that it cannot even penetrate an ordinary sheet of paper, and so actually never escapes the sealed glass tube.
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Related ResourcesTypes of Illumination - Radioluminescent
Download - USNRC Fact Sheet on Tritium Exit Signs
Why is additional address information required for purchasing tritium exit signs?
Self-luminous tritium exit signs are required by law to be registered with the U.S. Nuclear Regulatory Center (USNRC). Before an order can be processed for shipment, the following End User (where the tritium exit signs will actually be installed) Information will need to be provided:
- End User Company Name (for whom/where signs will be installed)
- End User Address of Installation (Street, State, Zip-code) (where the sign will be installed)
- End User Contact Name / Title / Email Address / Fax Number & Phone Number (who has overall responsibility for the sign)
How do you turn on tritium exit signs?
You do not have to do anything to activate tritium exit signs. Your self luminous exit sign is always on; just take it into a dark room and turn off the lights to view the illumination.
Why aren't tritium exit signs brighter?
They don't need to be. You may not be able to see the light emitted by the tritium tubes during normal lighting conditions, but the UL required contrast ratio of the face colors makes the self luminous exit signs very visible when you really need it, when the power has gone out, the self luminous exit signs become very visible. In fact, the brightness of tritium exit signs is more than twice the Underwriters Laboratories (UL) minimum requirement for emergency egress signage.
Are tritium exit signs approved?
Yes, self luminous tritium exit signs meet the requirements of the NFPA®, Life Safety Code 101® which is the bible for most fire codes. Other approvals/acceptances include: Underwriters Laboratories Inc. (UL), OSHA, NSI, BOCA, ICBO, SBCCI and the FAA (Commercial airliners have tritium exit signs to protect their passengers).
What is tritium?
Tritium gas is an isotope of the chemical element hydrogen that contains one proton, two neutrons and is naturally present in the atmosphere. Tritium is an unstable isotope, meaning that its molecular structure is subject to decay. 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 loses 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 1/2 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.
Is there radiation from tritium exit signs?
No. Tritium emits a beta electron which cannot even penetrate a piece of paper. The tubes in signs which contain the tritium 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.
What if a tube breaks?
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.
How long do tritium exit signs last?
Tritium has a short half-life, therefore the time that a tritium exit sign can effectively emit light is limited to only a few years. On initial purchase you can select tritium exit signs with a 10 or 20 year lifespan. Each self-luminous tritium exit sign has a sticker on it with an expiration date. The sign should be replaced before that date is reached.
What do I do with expired tritium exit signs?
Since tritium exit signs are registered, they require specific processing and documentation for disposal. Contact us to find out how we can help.