Basic Documentation

Table Of Contents
Biological Laboratories
Siemens Industry, Inc. 83
Topic Requirement(s) Commentary
Biological
Safety
Cabinets and
Classifications
(Continued)
Class II Type B1 cabinets
Minimum of 100 FPM (0.5m/s) inflow.
HEPA filtered largely uncontaminated recirculated air.
Exhausts most contaminated air to atmosphere through a dedicated duct
system.
Has negative pressure duct system or surrounded by a negative pressure
duct system.
Class II Type B2 cabinets
Minimum of 100 FPM (0.5m/s) inflow.
HEPA filtered non-recirculated, downward airflow.
HEPA filtered exhaust air to atmosphere.
Has negative pressure duct system or surrounded by a negative pressure
duct system.
8.4.3 Class III Cabinets
Description Provides absolute personnel protection, environmental
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protection and may provide product protection. It is characterized by a totally
enclosed, gas tight. negative pressure, HEPA filtered, ventilated workspace
accessed through attached rubber gloves and purged interchange chambers.
Exhaust air is treated by double HEPA filtration and/or incineration.
American Conference of Governmental Industrial Hygienists (ACGIH)
INDUSTRIAL VENTILATION A Manual of Recommended Practice, 27th Edition
10.35.2 Biological Safety cabinets
A laboratory hood…could be considered a Class I BSC if the exhausted air is
passed through HEPA filters prior to release to the atmosphere.
Type A cabinets that discharge into the work area are not recommended for use
with gasses or vapors.
ASHRAE, 2011 Handbook - HVAC Applications, Laboratories, Pg. 14.6, - 14.8
BIOLOGICAL SAFETY CABINETS
Class I Similar to chemical fume hood, no research material protection, 100%
exhaust through a HEPA filter
Class II Type A1 70% recirculation within the cabinet; 30% exhaust through a
HEPA filter; common plenum configuration; can be recirculated into the
laboratory
Type A2 70% recirculation within the cabinet; 30% exhaust through a HEPA
filter; common plenum configuration; can be recirculated to the room or
exhausted to the outside
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Environmental protection requires a HEPA filtering in the exhaust duct prior to discharging outdoors.