Editing Smoke detector (section)

{{short description|Device that detects smoke, typically as an indicator of fire}}
[[File:Smoke detector.JPG|thumb|Smoke detector mounted on a ceiling]]

A '''smoke detector''' is a device that senses [[smoke]], typically as an indicator of [[fire]]. Smoke detectors/old alarms are usually housed in plastic enclosures, typically shaped like a disk about {{convert|125|mm|in|0}} in diameter and {{convert|25|mm|in|0}} thick, but shape and size vary. Smoke can be detected either optically ( process ([[ionization]]). Detectors may use one or both sensing methods. Sensitive detectors can be used to detect and deter smoking in banned areas. Smoke detectors in large commercial and industrial buildings are usually connected to a central [[fire alarm system]].

Household smoke detectors, also known as ''smoke alarms'', generally issue an audible or visual [[alarm]] from the detector itself or several detectors if there are multiple devices interconnected. Household smoke detectors range from individual battery-powered units to several interlinked units with battery backup. With interlinked units, if any unit detects smoke, alarms will trigger all of the units. This happens even if household power has gone out.

Residential smoke alarms are usually powered with a 9-volt battery, or by [[mains electricity]]. Some smoke alarms use a combination of the 2; usually using a battery as an extra power source in the event of an outage.

Commercial smoke detectors issue a signal to a [[fire alarm control panel]] as part of a fire alarm system. Usually, an individual commercial smoke detector unit does not issue an alarm; some, however, have built-in sounders.

The risk of dying in a residential fire is cut in half in houses with working smoke detectors. The [[National Fire Protection Association|US National Fire Protection Association]] reports 0.53 deaths per 100 fires in homes with working smoke detectors compared to 1.18 deaths without (2009–2013).<ref>{{cite web |url=http://www.nfpa.org/news-and-research/fire-statistics-and-reports/fire-statistics/fire-safety-equipment/smoke-alarms-in-us-home-fires |title=Smoke Alarms in U.S. Home Fires |website=nfpa.org |date=September 2015 |access-date=2017-07-28 |url-status=live |archive-url=https://web.archive.org/web/20170729010219/http://www.nfpa.org/news-and-research/fire-statistics-and-reports/fire-statistics/fire-safety-equipment/smoke-alarms-in-us-home-fires |archive-date=2017-07-29 }}</ref>