Simply put, tritium is one of the most powerful technologies TRUGLO utilizes to make sights bright. It does not need batteries or need to be charged with light. It provides a constant glow for years. This makes it a great technology for emergency equipment like illuminated exit signs, watch hands, and handgun sights.
Tritium is a radioactive isotope of hydrogen. It gradually breaks down and decays into helium. As it decays, a small about of energy is gives off. The tritium vials found in gun “night sights” and wrist watches contain a small amount of tritium gas and phosphorus or other photo-sensitive materials. As the tritium breaks down and gives off energy. This energy (ionizing radiation) excites the phosphorus and causes it to glow. This creates a constant and steady glow for years.
The rated half life of tritium is approximately 12 years. This means that after twelve years, handgun sights will be approximately half as bright are when there were first sent to the dealer.
Tritium gas occurs naturally in the atmosphere. It is generally considered to be harmless, except in very high concentrations. The amount of tritium used in in wrist watches and handgun sights falls well below the amount considered to be harmful.
If a tritium vial ever breaks or leaks (which is rare), there is no required clean-up or precautionary handling procedure. Tritium is a pressurized buoyant gas that quickly dissipates and returns to the atmosphere.
Facilities that work with tritium and install tritium vials are heavily regulated by the United States Nuclear Regulatory Commission (USNRC) to ensure that maximum tritium quantities in a facility are within safe limits and that all tritium-related products are installed and maintained in a safe manner.
Here is an interesting article from guns.com about tritium night sights: