When door release equipment is required and the header from the top of the door to the ceiling is 28 inches on both sides, how many ceiling mounted smoke detectors are required?

• A. 1 detector
• B. 2 detectors
• C. 3 detectors
• D. 4 detectors

Answer: (B)

The main idea here is ensuring proper smoke detection coverage for a doorway that has release equipment. When a door release is required, you want detection on both sides of the door so smoke is detected no matter which side is affected and the release can happen promptly. With only 28 inches from the door header to the ceiling on each side, there isn’t a single ceiling-mounted detector location that can adequately cover both sides of the doorway. Placing one detector on each side of the door ceiling provides two distinct coverage zones right where the door interacts with the room, meeting the requirement for detectors near a door with release hardware. A single detector wouldn’t monitor both sides effectively, and adding more than two isn’t needed given the available space.