Elevator lobby smoke detectors must be mounted within a maximum distance of how many feet from the center-line of the door?

Elevator lobby smoke detectors are required to be installed within a specified distance from the center-line of the door to ensure effective smoke detection in areas that may be prone to smoke accumulation during a fire. The correct distance for mounting these detectors is a maximum of 21 feet from the center-line of the door. This placement is critical because it maximizes the likelihood of detecting smoke generated from a fire originating within or near the elevator shaft while minimizing false alarms caused by unrelated activities outside the elevator area.

By adhering to the standard of 21 feet, the safety and effectiveness of the smoke detectors in protecting the building occupants and enhancing fire safety protocols are maintained. This guideline is part of the building and fire codes to ensure that all life safety systems function correctly in emergencies.