(c) Anthony K. Grafton 2003

Americium in the House

The smoke detector in your house is probably nuclear powered. Well, sort of.

Many smoke detectors contain the radioactive element known as americium. But don’t worry. Only a very small amount of this element is present in each smoke detector, and the kind of radiation that it emits (alpha particles) is easily absorbed by a few centimeters of air, not to mention the much heavier parts of the smoke detector device itself that also easily protect us from the radiation. Your smoke alarm would only be dangerous to you if you broke open nearly every part inside the detector and managed to inhale some of the americium. (Don’t do this, because then it really would be hazardous to your health!)

Smoke detectors that contain americium work by using the natural radiation from this element to interact with the air inside what is called an ionization chamber. When an alpha particle from the americium is absorbed by air, it produces ions that allow a small electrical current to flow through the chamber. When smoke particles enter the ionization chamber, they interfere with the flow of this small current, and the resulting drop in current flow is what triggers the alarm.

Americium was discovered 57 years ago by the famous scientist Glenn Seaborg. Each year, only a few kilograms of americium oxide (a chemical compound of americium) are manufactured in this country. However, each gram of americium oxide is enough to manufacture several thousand smoke detectors. These smoke detectors then save hundreds of lives each year.

Some people expect scientific research to have obvious and immediate benefits to society. But the next time you hear of some seemingly-strange project being done by a scientist you’ve never heard of, look up at your smoke detector and think of the benefit we gain every day from the same nuclear research that gave us the atomic bomb.