SECTION 17: Tritium Exit Signs

Tritium exit signs may be found in some buildings at Princeton University. Each sign consists of sealed glass tubes internally coated with a phosphor and filled with tritium gas, which is radioactive. Radiation emitted by the tritium causes the phosphor to glow. These signs produce green light continuously for several years without any external power source and therefore typically are used in areas where providing electrical power is difficult. The signs are labeled with a “CAUTION RADIOACTIVE MATERIAL” warning on the back or side and are readily identifiable if you look closely at the sign. Unless damaged or broken, a tritium exit sign does not present any hazard. Although breakage is quite rare, release of the tritium in a single sign could require a decontamination effort costing many thousands of dollars.

EHS maintains an inventory of tritium exit signs on campus, and, whenever feasible, tritium exit signs are replaced with non-radioactive exit signs. Tritium exit signs found during renovations must be disposed of in accordance with federal regulations. EHS should be contacted to make proper disposal arrangements.

New tritium exit signs should not be used on campus and should not be specified for new construction or renovations.

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