Which statement about the maximum distance a heat detector can be from any point on a smooth ceiling is correct?

Which statement about the maximum distance a heat detector can be from any point on a smooth ceiling is correct?

• A. 0.5 times the listed spacing
• B. 0.7 times the listed spacing
• C. 1.0 times the listed spacing
• D. 1.5 times the listed spacing

Answer: (B)

Heat detectors are placed based on the listing’s stated spacing to ensure the whole ceiling area is covered. On smooth ceilings, every point should be within a limited distance of a detector, and that limit is 0.7 times the listed spacing. The 0.7 factor provides a safety margin to account for how heat disperses in a room and the detector’s response time, so even the farthest point reaches a detector quickly enough. If the listed spacing is, say, 16 units, the farthest point from a detector on a smooth ceiling should be no more than 11.2 units away (0.7 × 16). This approach avoids gaps in coverage while keeping installation practical; other factors would be either overly conservative or insufficient for reliable detection on a smooth ceiling.

Heat detectors are placed based on the listing’s stated spacing to ensure the whole ceiling area is covered. On smooth ceilings, every point should be within a limited distance of a detector, and that limit is 0.7 times the listed spacing. The 0.7 factor provides a safety margin to account for how heat disperses in a room and the detector’s response time, so even the farthest point reaches a detector quickly enough. If the listed spacing is, say, 16 units, the farthest point from a detector on a smooth ceiling should be no more than 11.2 units away (0.7 × 16). This approach avoids gaps in coverage while keeping installation practical; other factors would be either overly conservative or insufficient for reliable detection on a smooth ceiling.