Smoke detectors shall be mounted on the ceiling or wall at a point centrally located in the corridor or area giving access to the rooms used for sleeping purposes. Where a common hallway is used, smoke detectors shall be spaced not more than twenty-five feet apart in the hallway. All smoke detectors shall be located either on the ceiling at a minimum of six to twelve inches from the wall, or on a wall at a minimum of six to twelve inches from the ceiling, or as per manufacturer guidelines, and within fifteen feet of all rooms used for sleeping purposes. No detector shall be recessed into the ceiling. (Prior code § 8-30)