Tritium is a radioactive isotope of the element hydrogen. The chemical symbol for hydrogen is H. Tritium, symbol H3, occurs naturally in the atmosphere from the reaction of cosmic rays and air molecules. It is also produced in nuclear reactors during production of electricity. Tritium is composed of an atom of hydrogen with one proton and 2 neutrons giving it an atomic weight of 3.
Tritium has a half-life of about 12-1/2 years. This means that 1/2 of the original amount will decay in 12-1/2 years. While this half life is relatively brief in the world of radioactive materials, this gives tritium some useful properties. Tritium when encapsulated in watches, exit signs, aircraft gauges and other applications, will glow for up to 25 years.
The radioactive decay of tritium is not dangerous to man in these applications because it emits a very weak beta particle that can be stopped by even a piece of paper. Since the tritium is encapsulated in small packets made of glass or plastic, radiation doesn’t reach the skin.
The benefits of this decay is a bright display that can easily be read at night. The light emitted is not visible during the day, but at night, the glow is very visible. This makes tritium very popular for night visibility applications. Pilots, the military, police and others like the visibility without having to press any buttons to read the display.
Several watchmakers are now using tritium displays for their displays. They have displays that far exceed the brightness of standard luminescent watch dials that require “charging” by exposure to light. These have become very popular watch styles with the general public as well as military, pilots and law enforcement.