Why Are Smoke Detectors Radioactive?

Features

• According to the Environmental Protection Agency, 80 percent of all household smoke detectors in the United States contain a radioactive element, americium-241, with a half life of 432 years.

Function

• Americium-241 knocks an electron from molecules in the nitrogen and oxygen in the air. In regular circumstances, this creates a positive ion that becomes attracted to a negatively-charged metal plate within the device.

Effects

• When smoke is absorbed within the smoke detector, the positively-charged ions are absorbed before reaching the negatively-charged plate. This sets off the device, warning of a fire.

Significance

• Without the radioactive element within the smoke detector, the device would have to use an electronic method of detecting smoke. These electronic versions of smoke detectors are far more expensive than the standard household model.

Considerations

• Despite the radioactive properties within smoke detectors, americium-241 only releases alpha radiation. Alpha radiation can be blocked by millimeters of plastic casing, providing ample shielding for humans.