This quiz is on FIRE! by RobinJRichards

Question 13

Most household smoke detectors, especially the "ion chamber" variety, contain a very small amount of THIS ELEMENT. One gram of it can fill 5,000 detectors and it emits alpha particles of radiation, which create ions of oxygen and nitrogen in the detector. A small electrical charge (supplied by DC or AC power) usually catches these ions. But when smoke enters the detector, it absorbs the alpha particles, the ionization rate falls, and the electrical current dips, causing the alarm to sound.

Americium (241)