In large areas, ceiling detectors should be spaced at about how many feet apart?

• A. 15 feet
• B. 20 feet
• C. 30 feet
• D. 50 feet

Answer: (C)

In large spaces, detectors must cover the area so smoke doesn’t have to travel far before reaching a sensor. Ceiling-mounted detectors detect rising smoke best when their sensing zones overlap, giving reliable and timely detection across the area. Spacing them about 30 feet apart achieves this balance: it provides quick detection for most open layouts without unnecessary excess hardware. Placing detectors much farther apart, like 50 feet, could create gaps where smoke isn’t detected promptly. While closer spacing (15–20 feet) increases coverage, it adds cost and complexity without a proportional safety gain in large, open areas.