Ceiling smoke detectors should be placed at least how many feet from the wall?

• A. 15 feet
• B. 10 feet
• C. 5 feet
• D. 20 feet

Answer: (A)

Placing ceiling smoke detectors away from walls takes advantage of how air and smoke move in a room. Smoke rises and spreads along the ceiling, but the air right at walls and in corners can have slower movement or dead air, which can delay smoke reaching a detector. Setting a minimum distance from the wall—15 feet in this standard—ensures the detector sits in air that circulates more freely, allowing smoke to reach it quickly for a timely alarm. Choosing a smaller distance would place the detector in a zone where airflow is less reliable, increasing the chance of a slower or missed detection.