From Longman Dictionary of Contemporary Englishsmoke alarmˈsmoke aˌlarm (also smoke detector) noun [countable] TFIREa piece of electronic equipment which warns you when there is smoke or fire in a building The smoke alarm went off.
Examples from the Corpus
smoke alarm• If possible read the manufacturer's information and instructions before you buy a smoke alarm.• He didn't have a smoke alarm.• Smoking a cigarette will not normally set off a smoke alarm.• There are two basic types of smoke alarm.• The couple say that their smoke alarm, provided by the council, wasn't working. 