Three main types of smoke detectors:

– Ionization: Installed in an estimated 90 percent of American homes, they use the radioactive element americum-241 to set up an electrical current between two metal plates. When smoke interrupts the current, the alarm sounds. Ionization detectors work best in open, flaming fires.

– Photoelectric smoke detectors have an internal beam of light that is deflected by smoke particals, triggering the alarm. They work better – meaning sooner – in smoldering, smokey fires.

– Combination detectors have both types of sensor, ionization and photoelectric.

AP-ES-02-09-08 1251EST

Only subscribers are eligible to post comments. Please subscribe or to participate in the conversation. Here’s why.

Use the form below to reset your password. When you've submitted your account email, we will send an email with a reset code.