Abbreviation of 住宅用火災警報器 (residential fire alarm). Used in product names, safety guidelines, and everyday conversation about home fire safety.
See also: 住宅用火災警報器 (じゅうたくようかさいけいほうき)
I replaced the battery in the smoke detector because it ran out.
Installation of smoke alarms is mandatory in this apartment building.
General term for fire alarm devices, often used in commercial or public buildings. 住警器 specifically refers to residential smoke detectors.
Abbreviation formed from the first characters of 住宅 (じゅうたく, residential), 火災 (かさい, fire), and 警報器 (けいほうき, alarm device).