Spacing for spot type smoke detectors on a smooth ceiling (in the absence of specific performance based design criteria) can be up to how many feet?

• A. 35 feet
• B. 30 feet
• C. 25 feet
• D. 20 feet

Answer: (B)

Max spacing for spot-type smoke detectors on a smooth ceiling, when you don’t have performance-based design criteria, is thirty feet. This distance is chosen because smoke tends to rise to the ceiling and spread across it, so keeping detectors within 30 feet of each other helps ensure smoke reaches a detector quickly, enabling a prompt alarm. In practice, that means no point on the ceiling would be more than about fifteen feet from a detector if detectors are evenly spaced. If the ceiling is not smooth or has obstructions, or if performance-based criteria apply, spacing would be adjusted to maintain reliable coverage.