Basic Documentation

Table Of Contents
Laboratory Ventilation Codes and Standards
Siemens Industry, Inc. 80
Topic Requirement(s) Commentary
Biological
Safety
Cabinets and
Classifications
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National Sanitation Foundation, NSF 49 -2008, Biosafety Cabinetry: Design,
Construction, Performance and Field Certification
3 Definitions
3.4.1 Class I: A ventilated cabinet for personnel and environmental protection,
having an unrecirculated inward airflow away from the operator that exhausts all
air to the atmosphere after filtration through a HEPA filter. Class I cabinets are
suitable for work where no product protection is required.
NOTE Although the traditional Class I BSC is exhausted to the atmosphere
without recirculation into the lab, it is recognized that some of the benefits of the
Class I BSC can be obtained even when the unit’s HEPA filtered exhaust is
vented back into the laboratory.
3.4.2 Class II:
A ventilated cabinet for personnel, product, and environmental protection having
an open front with inward airflow for personnel protection, downward HEPA
filtered laminar airflow for product protection, and HEPA filtered exhausted air for
environmental protection.
NOTE When toxic chemicals or radionuclides are used as adjuncts to biological
studies or pharmaceutical work, Class II cabinets designed and constructed for
this purpose should be used.
3.4.2.1 Class II Type A1 cabinets (formerly designated Type A): cabinets that:
maintain minimum average inflow velocity of 75 ft/min (0.38 m/s) through the
work access opening;
have HEPA filtered downflow air that is a portion of the mixed downflow and
inflow air from a common plenum (i. e., a plenum from which a portion of the air
is exhausted from the cabinet and
the remainder supplied to the work area);
may exhaust HEPA filtered air back into the laboratory or to the environment
through an exhaust canopy; and
have all biologically contaminated ducts and plenums under negative pressure
or surrounded by negative pressure ducts and plenums.
Type A1 cabinets are not suitable for work with volatile toxic chemicals and
volatile radionuclides.
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