06-06
Table 3.2
PRESSURE
DROPS
SIZE
H7
H13
EXHAUST
EXHAUST
MAKE-UP
MILLIMETERS EXHAUST
ROOM
AUXILIARY
TOTAL
H7/H13
H13 ONLY
(CFM)
(CFM)
(CFM)
(CFM)
("WG)
("WG)
900(36")
18(625)
7(250)
11(375)
18(625) 89(0.36) 7.5(0.03)
1200(48")
25(875)
10(350)
15(525)
25(875) 75(0.30) 17(0.07)
1500(60")
32(1125) 13(450)
19(675) 32(1125) 80(0.32) 54(0.22)
1800(72")
39(1375) 15(550)
23(825
39(1375) 60(0.24) 82(0.33)
2400(96")
53(1875) 21(750) 32(1125) 53(1875) 100(0.40)139(0.56)
c. The auxiliary make-up air shall be filtered and heated to room
temperature by a central make-up air unit.
The designer shall compare the two schemes involving all room air
and the combination of auxiliary make-up air and room air before
advising the equipment specialist to select H7 or H13 hoods.
d. The ductwork shall be stainless steel or optional PVC coated
galvanized steel with spark-proof construction exhaust fan and
explosion proof motor.
4. H12, Biological Safety Cabinets (Hoods):
The National Sanitation
Foundation (NSF), Standard 49, has divided the Biological Safety
Cabinets (BSCS) into four different types, namely A, B1, B2, and B3.
These hoods are available in two sizes:
Nominal - 1200 mm (4 Feet)
and 1800 mm (6 Feet), and are classified as Class I or Class II.
Class II offers personal, product, and environmental protection
compared to limited protection offered by Class I and are, therefore,
more in use.
a. The exhaust air quantities m3/min (CFM) and pressure drops Pa
(Inches of Water Gage) for A and B3 cabinets are listed below in
Table 3.3.
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