With type B1 hood, the exhaust filter is within the hood casing; the mounting
is external with type B2 hood. Interlock the internal blower and external
blowers. Coordinate the filter height above B2 Hood in the case of B2 safety
cabinet with other disciplines.
(2) Add pressure drop for future loading of HEPA filters and duct work to the
pressure drops shown above for determining static pressures of exhaust fans.
(3) Provide an airflow control valve in the exhaust air stream to ensure
constant airflow through the exhaust air system.
(4) Coordinate the following accessories with the hood manufacturer.
(4.1) Provide an airtight damper on the exhaust side to isolate the hood for
service and maintenance.
(4.2) Provide air monitoring Device and provision for sound and visible alarm
at the hood and at the central ECC in the event the flow varies more than
plus or minus 5 percent of the normal value.
(4.3) Provide an airflow switch to sound an alarm in the event of an
interruption in exhaust fan operation.
(4.4) See Article 2.16 for the emergency power requirements.
2.11.3.4.3 Class III Special research application. 100 percent exhaust
through HEPA filters to outdoors.
systems with the following specific requirements:
2.11.3.5.1 The exhaust air quantities and pressure drops for H14 hoods are
listed below:
Table 2-18 H14 Hood Exhaust Air Requirements
Size
Exhaust Air
Pressure Drop
mm (Inches)
Cu M/Min (CFM)
Pa (Inches of Water)
1200 (48)
29 (1030)
156 (0.625)
1500 (60)
38 (1355)
125 (0.50)
1800 (72)
47 (1680)
187 (0.75)
2400 (96)
66 (2355)
187 (0.75)
2.11.3.5.2 Ductwork shall be stainless steel (type 316) welded construction.
Fan shall be acid resistant metallic or metallic covered with inorganic
(polyurethane) coating, and explosion proof motor.
2.11.3.5.3 Ductwork shall be short, straight, with minimum horizontal runs,
manifolds and sharp turns. The exhaust duct shall terminate by using a
vertical discharge, which shall extend well above the roof eddy zone.
2.11.3.5.4 Coordinate cold-water make-up connections and electrical power
requirements for heat tracing with other trades for the wash down cycle.
2.11.3.5.5 See Article 2.16 for emergency power requirements.
HVAC DESIGN MANUAL
2-35
HVAC SYSTEMS AND EQUIPMENT
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