Last night our smoke detector went off, woke me up and gave me a great sense of curiosity on how they work. Upon reading several sites, I found this little factoid for all those geeks like me out there. Many residential smoke detectors contain a small amount of the element Americium-241, a radioactive element, atomic number 95, that is produced in nuclear reactors by the decay of Plutonium. The Americium emits radiation which ionizes the air in a small chamber in the smoke detector. This supports a low-level electrical current then if smoke enters the chamber it breaks this current and the alarm goes off. See this site for more info. Cool stuff.
Published by theirishduck