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FIGURE 2 FIGURE 3
• Locate an alarm in every room where someone sleeps with the door closed.
The closed door may prevent an alarm not located in that room from waking
• Smoke, heat, and combustion products rise to the ceiling and spread horizon-
tally. Mounting the smoke alarm on the ceiling in the center of the room
places it closest to all points in the room. Ceiling mounting is preferred in
ordinary residential construction.
• For mobile home installation, select locations carefully to avoid thermal barri-
ers that may form at the ceiling. For more details, see MOBILE HOME INSTAL-
• When mounting an alarm on the ceiling, locate it at a minimum of 4” (10 cm)
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” (10 cm) and a maximum of 12” (30.5 cm)
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 feet (9.1 m) long.
• Install Smoke Alarms on sloped, peaked or cathedral ceilings at or within 3ft
(0.9m) of the highest point (measured horizontally). NFPA 72 states: “Smoke
alarms in rooms with ceiling slopes greater than 1 foot in 8 feet (.3m in 2.4
m) horizontally shall be located on the high side of the room.” NFPA 72
states: “A row of detectors shall be spaced and located within 3 ft (0.9m) of
the peak of the ceiling measured horizontally” (see FIGURE 3).