5
and Ventilating System
and with NFPA 72 National Fire Alarm Code.
(Both publications are available from the National Fire Protection Associa-
tion, Batterymarch Park, Quincy, Massachusetts.) The detector on the
return air side of the blower should be located at a point prior to exhaust-
ing air from the building or diluting return air with outside air. The detector
on the supply air side of the blower should be downstream of the blower.
Wire or program the detectors into the system so that they automatically shut
down the blowers and operate dampers as required.
Mounting of the Air Duct Housing (See Figure 3)
a. Affix the adhesive backed gaskets (Item 1) to the back of the detector
housing (2) so that the larger hole on the gasket lines up with the
sampling tube hole on the sampling chamber and the smaller hole
lines up with the housing mounting hole.
b. Affix the adhesive backed template (5) to the side of the ductwork.
c. Drill the four 0.110 diameter holes with a No. 35 drill bit and cut or
punch out two
7
/
8
-inch diameter holes as indicated on the template.
d. Attach the appropriate model housing to the air duct using two No. 10
1
1
/
2
inch screws (6) and also using two No. 10 1-inch screws (7) with
lockwashers (8).
e. Cut a 12 inch by 12 inch access hole in the duct adjacent to the
housing to permit checking and cleaning of the sampling tubes. The
access hole must be covered and sealed when not in use.
Sampling Tube Selection
To ensure accurate air sampling, there are four standard lengths of inlet
sampling tubes to choose from. To select the appropriate length, deter-
mine the outside width of the duct. Select the sampling tube nearest to,
but greater than, the duct width (Table 5). The outlet sampling tube for all
ducts is a fixed length of 4 inches (10.1 cm). Trim the inlet sampling tube
at the job site as described below.
TABLE 5
SAMPLING TUBE SELECTION CHART
Sampling Tube
Standard
Outside Duct Width
Model No.
Tube Length
1 ft 9
3
/
4
in or less
STA-2
2 ft
1 ft 9
3
/
4
in - 3 ft 3
3
/
4
in
STA-3
3 ft 6 in
3 ft 3
3
/
4
in - 6 ft 3
3
/
4
in or less
STA-6
6 ft 6 in
6 ft 3
3
/
4
in - 9 ft 9
3
/
4
in or less
STA-10
10 ft
Greater than 9 ft 9
3
/
4
in
Consult factory
Note:
Each model is manufactured with a different number and size of
sampling hole. Only the specific tube must be used for the
specifiedduct width.
