What are the applications of radiations technologies in smoke detectors?

Background

A smoke detector is a device that detects smoke, indicating a fire. Commercial, industrial, and mass residential devices issue a signal to a fire alarm system, while household detectors, known as smoke alarms, generally issue a local audible and/or visual alarm from the detector itself.

Most smoke detectors work either by optical detection (photoelectric) or by physical process (ionization), while others use both detection methods to increase sensitivity to smoke.

 Detectors using ionizing radiation from Americium 241 are cheaper.They can detect particles of smoke that are too small to be visible. It includes about 37 kBq or 1µCi of radioactive americium 241(241Am), corresponding to about 0.3 µg of the isotope. The radiation passes through an ionizing chamber, an air-filled space between two electrodes, and permits a small, constant current between the electrodes. Any smoke that enters the chamber absorbs the alpha particles, which reduces the ionization and interrupts this current, setting off the alarm.

 

Reference: Wikipedia