Tritium (3H or hydrogen 3) has a half-life of just over twelve years. The half-life is the amount of time it takes to decay half of a given sample's energy output. It decays into 3He or helium 3 by releasing an electron and an electron antineutrino. The electron and the electron antineutrino release over 18keV of energy, as beta radiation. Beta radiation cannot penetrate human skin and the only way to get it into the body is through ingestion.

Back to our sights...the sight capsules have a phosphor coating on the inside that glows when excited by beta radiation emitted by the tritium. Different color sights have different phosphor mixes.

Premature failure is most likely caused by the failure of the container or the phosphor coating. My guess is with the capsule failure. Hydrogen is a tiny little molecule and will get out of the most minute crack.

Russ, who actually studied physics and chemistry all those years ago.