Edwards Signaling 517FH - Manual (Page 3)

The next logical location for mounting detectors is on the
sidewall. Any detector mounted on the sidewall should be located
as near as possible to the ceiling. A detector mounted on the
sidewall should have the top of the detector between 4 in. and 12
in. (0.1 m and 0.3 m) from the ceiling.
The Spacing of Detectors. Where a room is too large for pro-
tection by a single detector (50ft. spacing), several detectors should
be used. It is important that they be properly located so all parts
of the room are covered.
Where the Distance Between Detectors Should Be Further Re-
duced. The distance between detectors is based on data obtained
from the spread of heat across a smooth ceiling. Where the ceil-
ing is not smooth, the placement of the detector should be tai-
lored to the situation.
For instance, with open wood joists, heat travels freely down
the joist channels so that the maximum distance between detec-
tors, 50 ft. (15 m), may be permitted to be used. However, heat
has trouble spreading across the joists, so the distance in this
direction should be ½ the distance allowed between detectors, as
shown in fig. 1, and the distance to the wall is reduced to 12 ½ ft.
(3.8 m). Since ½ x 50 ft. (15 m) is 25 ft. (7.6 m), the distance
between detectors across open wood joists should not exceed 25
ft. (7.6 m), as shown in fig. 1, and the distance to the wall is
reduced [ ½ x 25 ft. (7.6 m)] to 12.5 ft. (3.8 m). The detectors are
required to be mounted on the bottom of the joists and not up in
joist channels.
Walls, partitions, doorways, ceiling beams and open joists in-
terrupt the normal flow of heat, thus creating new areas to be
protected.
Fig. 1
PLACEMENT OF SMOKE ALARMS
For your information, the National Fire Protection Association’s
Standard 72, reads as follows:
“2-2.1.1.1 Smoke detectors shall be installed outside of each
separate sleeping area in the immediate vicinity of the bedrooms
and on each additional story of the family living unit including base-
ments and excluding crawl spaces and unfinished attics. In new
construction, a smoke detector shall be installed in each sleeping
room.”
Where to Locate the Required Smoke Detectors in Existing Con-
struction. The major threat from fire in a family living unit is at
night when everyone is asleep. The principal threat to persons in
sleeping areas comes from fires in the remainder of the unit; there-
fore, a smoke alarm(s) is best located between the bedroom ar-
eas and the rest of the unit. In units with only one bedroom area
on one floor, the smoke alarms should be located as shown in
Figure 2.
In family living units with more than one bedroom area or with
bedrooms on more than one floor, more than one smoke alarm
will be needed, as shown in Figure 3.
In addition to smoke alarms outside of the sleeping areas, Chap-
ter 2 of NFPA 72 requires the installation of a smoke alarm on
each additional story of the family living unit, including the base-
ment. These installations are shown in Figure 4. The living area
smoke alarms should be installed in the living room or near the
stairway to the upper level, or in both locations. The basement
smoke alarm should be installed in close proximity to the stairway
leading to the floor above. When installed on an open joisted
ceiling, the alarm should be placed on the bottom of the joists.
The alarm should be positioned relative to the stairway so as to
intercept smoke coming from a fire in the basement before the
smoke enters the stairway.
Figure 2: A SMOKE ALARM SHOULD BE LOCATED BETWEEN
THE SLEEPING AREA AND THE REST OF THE FAMILY LIVING
UNIT.
Where to Locate the Required Smoke Alarms in New Con-
struction. All of the smoke alarms specified for existing construc-
tion are required, and, in addition, a smoke alarm is required in
each bedroom.
Are More Smoke Detectors Desirable? The required number
of smoke alarms may not provide reliable early warning protec-
tion for those areas separated by a door from the areas protected
by the required smoke alarms. For this reason, it is recommended
that the householder consider the use of additional smoke alarms
for those areas for increased protection. The additional areas
include: basement, bedrooms, dining room, furnace room, utility
room and hallways not protected by the required smoke alarms.
The installation of smoke alarms in kitchens, attics (finished or
unfinished), or garages is not normally recommended, as these
locations occasionally experience conditions that can result in
improper operation.
Figure 3: IN FAMILY LIVING UNITS WITH MORE THAN ONE
SLEEPING AREA, A SMOKE ALARM SHOULD BE PROVIDED
TO PROTECT EACH SLEEPING AREA IN ADDITION TO
ALARMS REQUIRED IN BEDROOMS.