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Exit signs containing tritium

A glowing red exit sign in darkness
Environment, Great Lakes, and Energy

Exit signs containing tritium

Self-luminous exit signs containing the radioactive gas tritium are widely used in a variety of facilities across the United States, such as public and private office buildings, theaters, stores, schools, and churches - anywhere the public needs a rapid exit path. Those who possess tritium exit signs in Michigan are general licensees of the U.S. Nuclear Regulatory Commission (NRC) and are subject to certain reporting and handling requirements, including proper disposal of unwanted or unused signs.

Intact tritium exit signs pose little or no threat to public health and safety and do not constitute a security risk. However, the NRC requires proper accounting and disposal of all radioactive materials. Proper handling and accounting are important, because a damaged or broken sign could cause minor radioactive contamination of the immediate vicinity, requiring a potentially expensive clean up.

Use of tritium in exit signs

More than two million tritium exit signs are estimated to be in use in the United States. The signs do not require electricity or batteries, and are commonly installed in areas where electrical power is not conveniently accessible. They serve a safety function by remaining lit during power outages and emergencies.

The tritium gas is contained in sealed glass tubes. The insides of the tubes are lined with a phosphor. Low-energy beta particles emitted by the tritium bombard the phosphor, causing it to glow.

There are a couple ways to determine whether an exit sign near you contains tritium. The device should have a permanent warning label that mentions tritium (H-3), displays the three-bladed radiation warning symbol, and states "caution: radioactive materials." If the label is not readily observable, try extinguishing all lights in the vicinity. If the word exit is green, the sign contains tritium. If all four letters in exit are fully lit, the sign is working properly. If not, the sign may be damaged. In addition, as tritium exit signs age, they may not glow as brightly and may not meet building codes. When this happens, they should be replaced.

Tritium emits low-energy beta radiation that cannot penetrate a sheet of paper or clothing. If inhaled, it leaves the body relatively quickly. Tritium gas is odorless, colorless and tasteless, and is lighter than air.

Regulatory requirements

Manufacturers of tritium exit signs are "specific licensees," meaning they are licensed by the NRC or an Agreement State1. The signs are considered "generally licensed devices," because they are inherently safe enough to be handled or used by anyone with no radiation training or experience.

Although purchasers - known as "general licensees" - do not need authorization from the NRC or a state regulatory agency to possess the signs, they are subject to certain regulatory requirements regarding handling, transfer, and disposal of the signs.2 They are also subject to NRC inspection and enforcement action (typically civil fines) for violating those requirements. Manufacturers must inform purchasers of the exit signs of the regulatory requirements for generally licensed devices. The general licensee is required to designate an individual responsible for complying with the regulatory requirements.

Under NRC regulations, a general licensee using tritium exit signs:

  • Must NOT remove the labeling or radioactive symbol, or abandon a sign;
  • Must properly dispose of an unused sign (see below);
  • Must report to the NRC any lost, stolen, or broken signs;
  • Must inform the NRC of a name change or change of address;
  • Must inform the NRC of the general licensee's designated representative;
  • Must NOT give away or sell the sign to another individual, company, or institution unless the device is to remain in use at its original intended location; in such a case, the transferor is to notify the recipient of the regulatory requirements and must notify the NRC of the transfer within 30 days.

1 The NRC has agreements with 37 states under which the states assume regulatory jurisdiction over the commercial, industrial, and medical uses of radioactive materials. Michigan is currently not an Agreement State.

2 The regulatory requirements for generally licensed devices are spelled out in NRC Regulatory Issue Summary 2006-25.

Disposing of a tritium exit sign

The Conference of Radiation Control Program Directors (CRCPD) maintains a list of companies licensed to accept exit signs for disposal. Look for "H-3 Lights" in the list.

 

Within 30 days of disposing of a sign, the general licensee is required to file a report to the NRC that includes:

  • The device manufacturer's (or distributor's) name, model number, and serial number;
  • The name, address, and license number of the person receiving the device; and
  • The date of the transfer.

Reports should be sent to:

Director of NMSS Attention: GLTS
U.S. NRC
Washington, D.C., 20555-0001