# Ionizing Radiation & Fire Detection
Ionizing radiation is used very effectively in fire-detection devices. While there is a great deal of fear in society regarding ionizing radiation, radiation from smoke and fire detectors is not dangerous, and the benefits of using such devices far outweigh the risks.
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What is Ionizing Radiation?
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Ionizing radiation is radiation that removes electrons from atoms and molecules, thus creating positive ions. Ionizing radiation may be particles, such as protons, neutrons or nuclei of atoms, or it may be electromagnetic waves. In the case of electromagnetic waves, it is the more energetic waves that are ionizing. This includes some ultraviolet (UV) light, as well as all x-rays and gamma rays.
Function
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Alpha particles are helium nuclei with no electrons. Detectors contain a radioactive isotope called americium-241. A radioactive (or unstable) isotope is an element that releases energy as ionizing radiation. In the case of americium-241, radiation is released int he form of alpha particles (helium nuclei without the electrons) and gamma rays. The radiation produces an electrical current. Tiny amounts of smoke, even if invisible, disrupt the production of the current, setting off the alarm. Thus, detectors using this system respond quickly, even to fires that do not produce much smoke.
Risk
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According to the US Environmental Protection Agency, the americium radiation source in a typical fire detector has a total energy of no more than a millionth of a curie, a tiny amount, which is by no means dangerous. Since americium-241 has a long half-life (432 years), this small amount of energy is released very slowly.
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