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RadTown

Tritium in Exit Signs

Radiation Facts

  • Using tritium in exit signs allows the sign to remain lit if the power goes out.
  • Tritium is a radioactive isotope that needs special handling procedures.
  • Tritium is most dangerous when it is inhaled or swallowed.

Many exit signs contain tritium. Tritium is a naturally-occurring radioactive isotope of hydrogen that is often used to light up  a sign without batteries or electricity. Tritium exit signs will glow without electricity or batteries for more than 10 years. This is beneficial in areas where it is difficult to install electric signs (like above doors) and in emergency situations when power is lost.

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About Tritium in Exit Signs

Tritium is the radioactive form of hydrogen. It exists as a gas or as a liquid when combined with oxygen to form tritiated water. Tritium can be naturally produced or man-made.

Image of a lit tritium exit sign. Tritium exit signs glow in the dark, even when the power is out.

When mixed with certain chemicals, tritium becomes a continuous, self-powered light source. Tritium exit signs are marked with a permanent warning label. Tritium exit signs are useful because they do not require a traditional power source such as batteries or hardwired electricity. This means that tritium exit signs will remain lit if the power goes out. Additionally, tritium exit signs do not require a cord or additional power source, so they can be mounted in locations where traditional power sources do not exist.

No radiation is emitted from a working, unbroken, tritium exit sign. Damage to tritium exit signs is most likely to occur when a sign is dropped during installation or smashed in the demolition of a building. If a tritium exit sign is damaged, the tritium could be released.

Tritium emits beta particles. Beta particles can be stopped by a layer of clothing or by a thin layer of aluminum. Beta particles are most harmful when inhaled or swallowed. Internal contamination occurs when people swallow or breathe in radioactive materials, or when radioactive materials enter the body through an open wound or are absorbed through the skin. Learn the radiation basics.

If a tritium exit sign is broken, never tamper with it. Leave the area immediately and call for help. At school, you should report the damaged sign to a teacher, janitor or someone in the main office. In other buildings, you can report the problem to a security guard. Tritium must be inhaled or ingested in large amounts to pose a significant health risk.

Unwanted tritium exit signs may not be put into ordinary trash; they require special disposal. Tritium exit signs that are illegally put in ordinary landfills can break and contaminate the site. Owners of buildings are responsible for ensuring the safe operation and disposal of tritium exit signs.

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What You Can Do

  • Educate yourself. Learn to recognize tritium exit signs from battery or electronically powered exit signs. Tritium exit signs spell out the word “EXIT” in green or red glowing light when the lights are out. They should be labeled as having tritium inside. Also, learn to recognize a damaged tritium exit sign. All four letters in “EXIT” should be lit. If a letter or part of a letter is not lit, the sign may be damaged. Leave the area around a damaged tritium exit sign immediately.
  • Do not tamper with tritium exit signs. Never tamper with a tritium exit sign. Only trained professionals should handle damaged tritium exit signs.
  • Report damage. Report damaged tritium exit signs. At school, you should report the damaged sign to a teacher, janitor or someone in the main office. In other buildings, you can report the problem to a security guard. For additional information, contact your state radiation protection control program.

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