Smoke detector

Description

A combined sensor/alarm unit used to detect combustion products and alert building occupants. Smoke detectors were first produced in the early 1970s and are now required in a inhabitated buildings. Smoke sensors are either based on cloud ionization or photoelectric detection methods. Ionization cells use tiny amounts of a radioactive material to produce atmospheric ions. When smoke reacts with these ions, the measured current drops and sets off an alarm. Photoelectric cells detect the smoke particles when a light beam is obscured or scattered by particles in the air. Since ionization detectors are considered best for fast burning fires and photoelectric detectors are better at sensing smouldering fires, some new smoke detectors contains both types of sensors.

Synonyms and Related Terms

smoke alarm; détecteur de fumées (Fr.); detector de fumos (Port.);

Additional Information

www.firstalert.com

Sources Checked for Data in Record

• Dictionary of Building Preservation, Ward Bucher, ed., John Wiley & Sons, Inc., New York City, 1996

• Encyclopedia Britannica, http://www.britannica.com Comment: "smoke detector." Encyclopædia Britannica. 2005. Encyclopædia Britannica Premium Service 1 June 2005 .