How far away from the center line of the elevator door can a smoke detector...

Forelevator recall, smoke detectors must be located within a specific distance of thecenterline of the elevator door.

NFPA 72 (2022), Section 21.3.3.2:

“Smoke detectors used to initiate elevator recall shall be located on the ceiling within 21 in. (0.53 m) of the centerline of each elevator door…”

21 inches ≈1.75 feet, so themax allowable distanceis just under 2 feet — however, many designsallow up to 5 feetto account for spacing within a small lobby area.

Additionally:

NFPA 72 (2022), A.21.3.3.2 (Annex):

"...generally located within 60 in. (5 ft) of the centerline of the elevator door..."for code-compliant positioning in various jurisdictions.