Rare technical term for a smoke alarm; in everyday Japanese, 煙感知器 (けむりかんちき) is the standard word.
See also: 煙感知器 (けむりかんちき)
A 煙警報器 is a device also called a smoke detector.
煙感知器 is the common, everyday term for a smoke detector or smoke alarm. 煙警報器 is a rare synonym that may appear in older or very formal technical documents.
Compound of 煙 (smoke), 警報 (alarm), and 器 (device). The exact origin is uncertain, but it follows a standard technical naming pattern.