What is the listed spacing for spot-type smoke detectors according to NFPA 72?

What is the listed spacing for spot-type smoke detectors according to NFPA 72?

• A. 20 ft
• B. 40 ft
• C. 30 ft
• D. 50 ft

Answer: (C)

Spot-type smoke detectors are point sensors, so the layout is designed so every part of the protected space is within reach of a detector. NFPA 72 sets a maximum spacing of 30 feet for these detectors, ensuring that smoke rising and spreading toward the ceiling will be detected promptly. In practical terms, you place detectors along the ceiling so no location in the room is more than 30 feet from a detector. If you tried to space them farther apart—like 40 or 50 feet—there could be an area that goes undetected long enough for smoke to accumulate. A 20-foot spacing would be denser than necessary in many cases, but it’s still within the general concept; the standard target is 30 feet to balance effective detection with cost. In spaces with unusual geometry, higher ceilings, or obstructions, you may need more detectors to maintain that same coverage.

Spot-type smoke detectors are point sensors, so the layout is designed so every part of the protected space is within reach of a detector. NFPA 72 sets a maximum spacing of 30 feet for these detectors, ensuring that smoke rising and spreading toward the ceiling will be detected promptly. In practical terms, you place detectors along the ceiling so no location in the room is more than 30 feet from a detector. If you tried to space them farther apart—like 40 or 50 feet—there could be an area that goes undetected long enough for smoke to accumulate. A 20-foot spacing would be denser than necessary in many cases, but it’s still within the general concept; the standard target is 30 feet to balance effective detection with cost. In spaces with unusual geometry, higher ceilings, or obstructions, you may need more detectors to maintain that same coverage.