Tritium gas (chemical symbol H-3) is an isotope of hydrogen. It is colorless, odorless and lighter than air. Most of its physical characteristics are the same as hydrogen, but the atoms in tritium are slightly different, causing them to emit low energy radiation in the form of beta rays, or electrons. Tritium is considered "user friendly" because it has the lowest energy rating of any radioisotope. Tritium gas, like other radioisotopes, decays at a known rate. This is usually specified as the "half life" - the time taken to decay to half the initial energy. For tritium, this half life is about 12.3 years.

Light is produced from Tritium when the electrons (beta particles) from tritium energize a phosphor compound which coats the inside of the glass tritium tubes. Phosphor has the property of emitting light when stimulated by electrons, and is used in television tubes and fluorescent lights. The surface of the tritium tube emits light continuously when the phosphor layer is energized.

Technically speaking, tritium products are radioactive, because they contain radioactive material. But in actuality they are not, because no radiation is emitted by the product. In other words, each product contains radioactive material, but the product itself is not "radioactive". Sealed safely inside the product, tritium gas is hermetically sealed into Pyrex glass tubes. The glass tubes completely stop all radiation. Actually, Tritium beta emissions are so weak that even in free air, the particle can only travel less than 1/4 inch. A sheet of tissue paper will stop it. If the tubes break and tritium is released from broken tubes, and the product somehow becomes unsealed, the product could emit a very small amount of radiation - but not enough to be harmful. In fact, the products are very tough, and it would be almost impossible to accidentally break tubes in an installed product. MEPROLIGHT products are built and tested to withstand a battery of stringent requirements, including mechanical shock or drop tests, temperature cycling and vibration.

But let's assume that someone deliberately sets out to destroy the product. We will assume the most conservative, or the "worst case scenario". We can calculate the potential radiation dose assuming that all tubes in a typical product are broken, which in practice would require the outer case and all inner parts to be broken. Released Tritium gas will behave exactly like hydrogen--it's very light and dilutes rapidly in air--which reduces the amount anyone can breathe. But we assume that somehow, a person is standing with his/her face literally inches away from the product, breathing hard for at least 5 minutes during and after a breakage, and absorbs all the Tritium. Under these extremely conservative and unrealistic conditions a person might get a radiation dose about same as a tooth x-ray. Clearly, this is not hazardous.