Basic Documentation

Table Of Contents
Laboratory Ventilation Codes and Standards
Siemens Industry, Inc. 82
Topic Requirement(s) Commentary
Biological
Safety
Cabinets and
Classifications
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3.4.3 Class III: A totally enclosed, ventilated cabinet of leak-tight construction.
Operations in the cabinet are conducted through attached rubber gloves. The
cabinet is maintained under negative air pressure of at least 0.50 in w.g. (120
Pa). Downflow air is drawn into the cabinet through HEPA filters. The exhaust air
is treated by double HEPA filtration or by HEPA filtration and incineration.
Scientific Equipment & Furniture Association
SEFA 12006 Recommended Practices for Laboratory Fume Hoods
8.4.1 Class I Cabinets
Description
A ventilated cabinet that provides personnel and environmental
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protection. It is
characterized by an unrecirculated inward flow of air away from the operator
through a limited fixed access opening. Exhaust air must be HEPA filtered if
recirculated back into the laboratory. It may or may not be vented via a remote
ventilation system. This cabinet does not offer product protection.
8.4.2 Class II Cabinets
Description A ventilated cabinet that provides personnel, product and
environmental
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protection. It is characterized by a limited fixed inward airflow
access opening that provides personnel protection, a vertical downward HEPA
filtered work zone that provides product protection and HEPA filtered exhaust
providing environmental protection. They are divided into types by the NSF and
Identified in Standard 49.
Class II Type A1 cabinets (Formally designated Type A)
Minimum of 75 FPM (.36m/s) inflow.
HEPA filtered downflow mixed with recycled air.
May exhaust some or all HEPA filtered air back into the laboratory.
May have positive pressure duct system.
Class II Type A2 cabinets (Formally designated Type B3)
Minimum of 100 FPM (0.5m/s) inflow.
HEPA filtered downflow mixed with recycled air.
May exhaust some or all HEPA filtered air back into the laboratory.
Has negative pressure duct system.
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Environmental protection requires a HEPA filter in the exhaust air stream prior to release outdoors.