How close can a wall-mounted smoke detector be to the ceiling?

• A. Two inches from the ceiling
• B. 4-12 inches from the ceiling
• C. More than 24 inches from the ceiling
• D. Exactly 18 inches from the ceiling

Answer: (B)

For wall-mounted smoke detectors, place them 4 to 12 inches below the ceiling. This placement keeps the sensor high enough to catch rising smoke quickly but far enough from the very top where air can be stagnant or swirled in dead-air pockets. If it’s mounted too close to the ceiling (like within a couple of inches), smoke may not reach the sensor promptly. If it’s mounted too far down (more than about 12 inches), detection can be delayed. Exactly 18 inches or more than 24 inches from the ceiling would be outside the recommended range and could slow the alarm.