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While tritium has several different experimentally determined values of its half-life, the National Institute of Standards and Technology lists 4,500±8 days (approximately 12.32 years).[1] It decays into helium-3 by beta decay and it releases 18.6 keV of energy in the process. The electron's kinetic energy varies, with an average of 5.7 keV, while the remaining energy is carried off by the nearly undetectable electron antineutrino. Beta particles from tritium can penetrate only about 6.0 mm of air, and they are incapable of passing through the dead outermost layer of human skin.[2] The unusually low energy released in the tritium beta decay makes the decay (along with that of rhenium-187) an appropriate laboratory for absolute neutrino mass measurements (the most recent experiment being KATRIN).
Tritium is potentially dangerous if inhaled or ingested. It can combine with oxygen to form tritiated water molecules, and those can be absorbed through pores in the skin.
The low energy of tritium's radiation makes it difficult to detect tritium-labeled compounds except by using liquid scintillation counting.
