Radiation is part of the natural environment: radiation from space passes through Earth’s atmosphere, while radiation from decaying isotopes in the Earth’s crust reaches the surface. But radiation is also part of most Canadians’ homes, in a variety of devices that residents make use of every day. In some cases, the presence of radioisotopes in these devices is required by law – and can even save lives.
Here are a few of the more common, less known nuclear devices around the home.
Smoke detectors are the most common consumer product that uses nuclear technology. They work by putting a source of alpha radiation, usually Americium-241, near an ion detector. The alpha particles coming off of the source cause ionization in the air molecules – that is, they separate an electron from the rest of the molecule, leaving the two halves with an electric charge. The electric charge is detectable by a positive and negative charged plate (shown below). When there is a certain concentration of smoke in the air, the charge drops, and the electronics in the detector sound an alert. This design allows smoke detectors to work for a long time, because Americium-241 has a half-life of 458 years.
Source: Teaching Advanced Physics.
Emergency exit signs help illuminate dark corridors during a power outages to help guide people to safety. They don’t run on backup power, because they have to function even when backup power fails. Instead, they’re powered by tritium, a radioactive isotope of hydrogen. Tritium releases beta particles that produce fluorescent light when they interact with phosphor-containing material in the sign.
Trace levels of radioactivity may also come from other common home items that contain radioactive elements. For example, many Canadian homes feature granite countertops. Because granite is cooled magma, it contains a mixture of many elements, including some radioactive isotopes. The specific composition will vary from sample to sample, but it is common for granite to contain trace levels of uranium, radium, and thorium.
Some antique items, such as Vaseline glass and fiestaware dishware, contain trace levels of radioactivity, as both of these were imbued with uranium for colouration purposes.
In each of these cases, the levels of radioactivity are very low and extremely safe.