H7 Hoods
H13 Hoods
Pressure Drop
ExhaustH Make-up
Total
Auxiliary
Room
Size mm
Exhaust
H13 ONLY
7/H13
Cu M/Min
Cu M/Min
Cu M/Min
(Inches) Cu M/Min
Cu M/Min Cu M/Min
(CFM)
(CFM)
(CFM)
(CFM)
(CFM)
(CFM)
2400
53
21
32
53
100
139
(96)
(1875)
(750)
(1125)
(1875)
(0.40)
(0.56)
(c) The auxiliary make-up air shall be filtered and heated to room
temperature by a central make-up air unit. See Paragraph 2.3.2 for filtration
requirements.
(d) The designer shall compare the two schemes involving all room air and the
combination of auxiliary make-up air and room air and make recommendation to
the VA before the selection of the hood.
(e) The ductwork shall be stainless steel or optional PVC coated galvanized
steel with spark-proof construction exhaust fan and explosion proof motor.
(f) See Article 2.16 for emergency power requirements.
2.11.3.4 BIOLOGICAL SAFETY CABINETS (HOODS) H12: A biological safety cabinet
protects the researcher, and in some configurations, the research materials
as well. Biological safety cabinets are sometimes called safety cabinets,
ventilated safety cabinets and glove boxes. These safety cabinets are
categorized into three classes and six groups. The National Sanitation
Foundation (NSF), Standard 49, has divided the Biological Safety Cabinets
(BSCs) into Class I, II, and III Cabinets. Class II Cabinets are of four
different types, namely A, B1, B2, and B3. These hoods are available in two
sizes (nominal): 1200 mm (4 ft) and 1800 mm (6 ft). Class II offers personal,
product, and environmental protection compared to the limited protection
offered by Class I and are, therefore, more in use. Class III Cabinets are
rarely used. All Class II Cabinets require HEPA filters for the downflow and
exhaust air system.
2.11.3.4.1 Class I: Similar to chemical fume hoods, no research material
protection, 100 percent exhaust through a HEPA filter. Provide a dedicated
exhaust system for each B1 or B2 hood, i.e. each hood must have its own
independent exhaust fan and duct work. The ductwork shall be stainless steel
or optional PVC coated galvanized steel.
2.11.3.4.2 Class II: Biological Safety Cabinet configurations are as per
ASHRAE Applications Handbook, 1999.
(a) Type A: 70 percent recirculation within the cabinet, 30 percent exhaust
through a HEPA filter, common plenum configuration, can be recirculated into
the laboratory.
(b) Type B1: 30 percent recirculation within the cabinet, 70 percent exhaust
through a HEPA filter, separate plenum configuration, must be exhausted to
the outside.
(c) Type B2: 100 percent exhaust through a HEPA filter to the outside.
HVAC DESIGN MANUAL
2-33
HVAC SYSTEMS AND EQUIPMENT
Previous Page
