> It's not IR and the rules are very different. Beta-emitters aren't dumping that energy into thermal heating, they're dumping it into the interior of your cell

> It's not IR and the rules are very different. Beta-emitters aren't dumping that energy into thermal heating, they're dumping it into the interior of your cells as a high energy electron or positron. Wherever that thing appears, it's quite likely to blow a hole through whatever substructure happens to catch it, which means despite being low overall energy, the delivery mechanism is quite different. Ok, I get your point now: even if low power, by being ionizing radiation, it can break molecular bonds, create dislocations in crystals, alter enzymes etc. However, the tritium radiation just not very penetrating. Even if it has enough energy to ionise several atoms, it deposits that energy superficially, where cells are already dead. The layer of skin sensitive to radiation is just too deep compared to the maximum distance the electrons can travel: 40 μm vs 5 μm. The sensitive tissues in the eye are even deeper: 3 mm. In facilities that handle tritium there are containment systems but, really, there is no special radiation shielding. The only way for this radiation to to do real damange, is if the tritium is inhaled or absorbed into the skin. But even then, due to a series of factor like the low energy radiation and the short biological half-life, the dose per unit intake is very very low (~10⁻¹¹ Sv/Bq). I'm saying most of this based on the book "Safety in Tritium Handling Technology", which I'm currently studying, but I really can't find any mention of accidents or concerns about what you say regarding tritium.