When mounted on a wall, the top of a smoke detector must be within how many inches of the ceiling?

When mounted on a wall, the top of a smoke detector must be within how many inches of the ceiling?

• A. 12 inches
• B. 6 inches
• C. 18 inches
• D. 24 inches

Answer: (A)

Smoke rises toward the ceiling, so a wall-mounted detector needs to be placed high enough to intercept that smoke quickly. The top edge of a wall-mounted smoke detector should be no more than 12 inches below the ceiling. If it sits farther down the wall, smoke has to travel farther before reaching the sensor, delaying the alarm. The other distances exceed what’s recommended (or aren’t the maximum allowed), so 12 inches is the correct limit.

Smoke rises toward the ceiling, so a wall-mounted detector needs to be placed high enough to intercept that smoke quickly. The top edge of a wall-mounted smoke detector should be no more than 12 inches below the ceiling. If it sits farther down the wall, smoke has to travel farther before reaching the sensor, delaying the alarm. The other distances exceed what’s recommended (or aren’t the maximum allowed), so 12 inches is the correct limit.