Tritiated exit signs

A recent comment to my blog stated that there are tritiated exit signs, typically used in dark places such as movie theaters, where there is a need for signs if there is a power failure.   He stated that these signs have billions of Becquerels and I was able to confirm his facts.

The quantity of tritium contained in each tritium exit sign varies with the size of the sign. The tritium exit sign used in Hong Kong may contain tritium with total activity ranging from 0.3 to 0.8 TBq (300 to 800 billion Becquerel (貝克勒爾)).

The NRC states

Many kinds of facilities across the United States use tritium EXIT signs, including public and private office buildings, theaters, stores, schools and churches. The NRC estimates there are more than 2 million tritium EXIT signs in use in the United States.

Tritium is also used in watches

tritiated watch

Tufts University has banned the use of tritiated exit signs

Can tritium-containing exit signs be used at Tufts?

No. Tritium exit signs are sold under a general license from the US Nuclear Regulatory Commission. Intact signs can be handled without special precautions except to avoid damaging the sign. However, they contain very large amounts of radioactive material in the form of tritium gas. These signs should not be purchased or used at Tufts University.  Costs can be very high when it is time to dispose of these signs. There are only a limited number of disposal options for them. Some universities have paid thousands of dollars to dispose of just a few tritium exit signs. There have also been incidents where cleanup from damaged tritium exit signs has cost tens of thousands of dollars. Special training is required to ship tritium exit signs.

Tritium produces ionizing radiation.   The more the exposure to radiation, the greater the risks to biological tissues.  Because the signs are common does not mean that they are safe.   There are warnings about the disposal of these signs.  They cannot be disposed of in landfills, according to the NRC.

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