TRITIUM LIGHT SOURCES are made using glass tubes with a phosphor layer in them and tritium (a hydrogen isotope) gas inside the tube. Such a tube is known as a "gaseous tritium light source" (GTLS).

Unlike traditional light sources using in watches, it doesn't need any external battery, charging of light and other maintaining. They are 100 times brighter than other sources comparable in watches.


These light sources are most often seen as "permanent" illumination for the hands of wristwatches intended for diving, nighttime, or "tactical" use. They are additionally used in glowing novelty keychains and in self-illuminated exit signs. They are also favored by the military for critical applications where illumination of the glow-in-the-dark sort is desired but a light source may not be available. Some uses of this sort are analog dials in aircraft, in compasses, and sights for weapons.

Health Concern

While they contain a radioactive substance, self-powered lighting does not pose a significant health concern. Tritium presents no external radiation threat when encapsulated in non-hydrogen-permeable containers. This is due to the fact that beta decay radiation from tritium is not very energetic; it is incapable of penetrating through glass containers or even intact human skin. Direct, short-term exposure to small amounts is relatively harmless. If a tritium tube should break, one should leave the area and allow the gas to diffuse into the air. Tritium exists naturally, but in very small quantities.