Household smoke detectors
Radionuclides are present in many homes as they are used inside the most common household smoke detectors. The radionuclide used is americium-241, which is created by bombarding plutonium with neutrons in a nuclear reactor. It decays by emitting alpha particles and gamma radiation to become neptunium-237. Smoke detectors use a very small quantity of 241Am (about 0.29 micrograms per smoke detector) in the form of americium dioxide. 241Am is used as it emits alpha particles which ionise the air in the detector's ionization chamber. A small electric voltage is applied to the ionised air which gives rise to a small electric current. In the presence of smoke some of the ions are neutralized, thereby decreasing the current, which activates the detector's alarm.
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