What is the required distance (within) between a smoke detector and the centerline of an elevator opening?

• A. No specific distance required.
• B. Within 5 feet.
• C. More than 30 feet.
• D. Within 21 feet.

Answer: (D)

Smoke detectors in elevator lobbies are placed so smoke is detected quickly to trigger elevator recall and the fire alarm system before people try to use the elevator. The standard requires the detector to be no farther than 21 feet from the centerline of the elevator opening. This distance strikes a balance: it ensures fast detection in the lobby area without being so close as to cause nuisance alarms. If the detector were placed farther than 21 feet, smoke could reach the lobby and the detector too slowly, delaying recall and alerting actions. A distance of only a few feet is unnecessary and not required, while a much larger distance would not meet the code.