Spot-type heat detectors shall be within what fraction of the listed spacing, measured at right angles from walls?

Spot-type heat detectors shall be within what fraction of the listed spacing, measured at right angles from walls?

• A. One third
• B. One quarter
• C. One half
• D. One fifth

Answer: (C)

Spot-type heat detectors are designed with a listed spacing that sets how far apart detectors can be along the ceiling. But near walls, you need closer placement to avoid detection gaps because the heat plume interacts differently with walls and may not reach detectors as easily. Therefore, the detector must be located within half of the listed spacing from the wall, measured perpendicular to the wall. For example, if the listed spacing is 20 feet, the first detector along the wall should be no more than 10 feet from the wall. This ensures that every point in the space is within reach of a detector’s sensing area. The half-spacing requirement balances effective coverage with practical installation, avoiding unnecessary density while still preventing gaps near walls.

Spot-type heat detectors are designed with a listed spacing that sets how far apart detectors can be along the ceiling. But near walls, you need closer placement to avoid detection gaps because the heat plume interacts differently with walls and may not reach detectors as easily. Therefore, the detector must be located within half of the listed spacing from the wall, measured perpendicular to the wall.

For example, if the listed spacing is 20 feet, the first detector along the wall should be no more than 10 feet from the wall. This ensures that every point in the space is within reach of a detector’s sensing area. The half-spacing requirement balances effective coverage with practical installation, avoiding unnecessary density while still preventing gaps near walls.