Smoke detectors installed in elevator lobbies for Phase I recall must be installed within how many feet of the centerline of each elevator car controlled by the detector?

• A. 15 feet
• B. 21 feet
• C. 25 feet
• D. 30 feet

Answer: (B)

In elevator recall, detectors in the lobby are placed so that the system can sense smoke quickly near the elevator cars and initiate Phase I recall without delay. The standard distance is within 21 feet of the centerline of each elevator car controlled by that detector. This placement ensures smoke in the immediate lobby area around the car is detected promptly, triggering the recall to a safe floor and preventing occupants from using the car as smoke conditions rise. If detectors were farther away, detection could be delayed and recall actions slower, which could increase risk. The 21-foot rule represents a practical coverage distance that balances effective detection with typical lobby layouts.