Ceiling mounting is preferred in ordinary residential construction. 
•  For mobile home installation, select locations carefully to avoid 
thermal barriers that may form at the ceiling.  For more details, 
see MOBILE HOME INSTALLATION below.
•  When mounting an alarm on the ceiling, locate it at a minimum 
of 4” (10cm) from the side wall (see figure 1).
•  When mounting the alarm on the wall, use an inside wall with 
the top edge of the alarm at a minimum of 4” (10cm) and a 
maximum of 12” (30.5cm) below the ceiling (see figure 1).
•  Put smoke alarms at both ends of a bedroom hallway or large 
room if the hallway or room is more than 30 ft (9.1m) long.
•  Install Smoke Alarms on sloped, peaked or cathedral ceilings 
at or within 3 ft (0.9m) of the highest point (measured hori-
zontally). NFPA 72 states: “Smoke alarms in rooms with ceiling 
slopes greater than 1 ft in 8 ft (.3m in 2.4m) horizontally shall 
be located on the high side of the room.” NFPA 72 states: “A 
row of alarms shall be spaced and located within 3 ft (0.9m) of 
the peak of the ceiling measured horizontally” (see figure 3). 
FIGURE 2 FIGURE 3
FIGURE 1
0305-7226-00(21008148-EN A).indd   30305-7226-00(21008148-EN A).indd   3 2010.10.6   9:29:25 AM2010.10.6   9:29:25 AM