It’s widely known that a smoke detector is a good ionizing radiation source, as they contain a small amount of americium-241, a side product of nuclear reactors. But what about other sources?

A smoke detector of this type uses a metal shell to house a tiny sample of radioactive americium that emits alpha particles into the space between two electrodes. These ionise the air in that ...

Let’s start with the two basic types of smoke detectors. Ionized. A small amount of radioactive material is placed in a chamber to ionize the air, creating a continuous electric current.