A spot-type heat detector located on a wall shall not be more than ____ inches from the ceiling.

A spot-type heat detector located on a wall shall not be more than ____ inches from the ceiling.

• A. 6
• B. 9
• C. 18
• D. 12

Answer: (D)

Spot-type heat detectors sense the rising heat near the ceiling, so when mounting on a wall you want the sensing element to be close to that hot air layer. Keeping the detector within 12 inches of the ceiling ensures a quick response to a developing fire and aligns with standard installation guidelines. If you place it farther down the wall, heat from a ceiling-level fire can stratify above the device, delaying detection. Therefore, the maximum allowed distance is 12 inches. Placing it closer, like 6 or 9 inches, is still acceptable, but 18 inches would exceed the limit.

Spot-type heat detectors sense the rising heat near the ceiling, so when mounting on a wall you want the sensing element to be close to that hot air layer. Keeping the detector within 12 inches of the ceiling ensures a quick response to a developing fire and aligns with standard installation guidelines. If you place it farther down the wall, heat from a ceiling-level fire can stratify above the device, delaying detection. Therefore, the maximum allowed distance is 12 inches. Placing it closer, like 6 or 9 inches, is still acceptable, but 18 inches would exceed the limit.