About Tritium

Tritium (Hydrogen-3) is an isotope of hydrogen gas. It can be man-made, but it is also a naturally occurring substance that is produced by cosmic ray action and by the decay of natural radionuclides in rocks and soil. It is a colourless, odorless gas, lighter than air. It is present in air and water all over the earth and is regularly ingested and breathed by everyone. All humans contain trace amounts of tritium and several other naturally occurring radioisotopes.

Many isotopes are stable and retain their structure indefinitely. However, some isotopes, including tritium, are not stable and are said to be radioactive. As the tritium nucleus decays it emits an electron, causing energy to be released in the form of beta radiation. A new nucleus is then formed with two protons and one neutron thereby becoming a form of non-radioactive helium.

Tritium beta emissions are very weak. No other primary radiation is emitted. In fact, tritium emits the lowest level of beta radiation energy of all isotopes. The beta particles are easily stopped by thin layers of any solid material and are unable to penetrate our body’s skin.

The light source in a self-luminous exit sign consists of borosilicate glass tubes, internally coated with phosphor and energized with tritium gas. As the tritium decays, it emits low level beta radiation that stimulates the phosphor, causing it to emit light. This beta radiation is completely contained within the glass tubes. Therefore, in a normal usage situation, there is absolutely no risk of radiation exposure from a self-luminous sign.

Nevertheless, as required by Federal Government, we have calculated the maximum radiation dose which could occur in the unlikely event that a self-luminous sign is totally destroyed and the tritium gas is released into a small closed area. For the purposes of this calculation, we have made very conservative assumptions: a person exposed continuously for one hour in a small closed area (3,000 square feet) with low ventilation (less than 1 air change per hour). In this scenario the radiation dose to the individual is approximately 30 millirem. To put this in perspective, this is roughly the equivalent to the radiation exposure received from one dental X-Ray and less than one half of the radiation dose received from natural sources each year.

In a more realistic situation, the signs will typically be installed in hallways and larger rooms where the ventilation rates would be far higher and the personal exposure would be significantly shorter than that used in the above calculation. In these real life situations, the radiation exposure would be less than 10 millirem.

Since tritium gas cannot penetrate the skin, the radiation exposure is received through the lungs where it mixes with the body fluids. Tritium is not absorbed by the bone marrow or other body organs and instead is expelled from the body through urination in a very short period of time.
Self Luminous Safety Signs pose no health risk in a normal use situation or even in the unlikely worst case scenario outlined above. They are the most reliable light source available. There are no defective circuits, batteries or burnt out lamps to worry about and are unaffected by power outages or brown outs. When all else fails, Self Luminous Safety Signs still function.

The chart that follows depicts some of the everyday radiation that we are exposed to in the course of our normal existence.