Tritium (H-3) is a weakly radioactive isotope of the element hydrogen that occurs both naturally and during the operation of nuclear power plants. Tritium has a half-life of 12.3 years and emits a weak beta particle. The most common form of tritium is in water, since tritium and normal hydrogen react with oxygen in the same way to form water. Tritium replaces one of the stable hydrogens in the water molecule, H2O, and creates tritiated water, which is colorless and odorless.
Tritium can be found in self-luminescent devices, such as exit signs in buildings, aircraft dials, gauges, luminous paints, and wristwatches. It is also used in life science research and in studies investigating the safety of potential new drugs. Click here for more information from the EPA.