Biosafety cabinets are workstations that provide protection for personnel, the environment, and products during work with infectious microorganisms. They incorporate HEPA filters in the exhaust and/or supply systems to remove airborne particles. The level of protection provided depends on the filter configuration and airflow direction. Biosafety levels 1-4 describe increasing containment for work with pathogens based on risk. Class I, II, and III cabinets provide different levels of containment depending on air recirculation, exhaust, and connections to facility ventilation systems.

1. Biosafety Cabinets
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2. Biosafety cabinets
 BSCs are only one part of an overall
biosafety program, which requires
consistent use of good microbiological
practices, use of primary containment
equipment and proper containment
facility design.
 BSCs were developed as
workstations to provide personnel,
environmental and product protection
during the manipulation of infectious
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3. BSCs
 Various types of containment and
clean air devices incorporate the use
of HEPA filters in the exhaust and/or
supply air system to remove airborne
particulate material.
 Depending on the configuration of
these filters and the direction of the
airflow, varying degrees of personnel,
environmental and product protection
can be achieved.
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4. BSCs
 Biosafety levels:
 Level 1:
 work is done with defined and
characterized strains of viable
microorganisms not known to
consistently cause disease in healthy
adult humans.
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5.  Level 2:
 work is done with the broad spectrum of
indigenous moderate-risk agents that are
present in the community and associated
with human disease of varying severity.
 Level 3:
work is done with indigenous or exotic
agents
with a potential for respiratory
transmission, and which may cause
serious and potentially lethal infection.
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6.  Level 4:
 work with dangerous and exotic
agents that pose a high individual risk
of life-threatening disease, which may
be transmitted via the aerosol route
and for which there is no available
vaccine or therapy.
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8. BSC principle
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9. Figure 2. The Class I BSC (A) front opening; (B) sash; (C) exhaust HEPA
filter; (D) exhaust plenum. Note: The cabinet needs to be hard connected to
the building exhaust system if toxic vapors are to be used.
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11. Figure 3. The Class II, Type A1 BSC (A) front opening; (B)
sash; (C) exhaust HEPA filter; (D) supply HEPA filter; (E)
common plenum; (F) blower.
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12. Figure 5A. The Class II, Type B1 BSC (classic design) (A) front opening; (B)
sash; (C) exhaust HEPA filter; (D) supply HEPA filter; (E) negative pressure
dedicated exhaust plenum; (F) blower; (G) additional HEPA filter for supply
air. Note: The cabinet exhaust needs to be hard connected to the building
exhaust system.
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13. Figure 8. The Class III BSC (A) glove ports with O-ring for attaching arm-length gloves
to cabinet; (B) sash; (C) exhaust HEPA filter; (D) supply HEPA filter; (E) double-ended
autoclave or pass-through box. Note: A chemical dunk tank may be installed which
would be located beneath the work surface of the BSC with access from above. The
cabinet exhaust needs to be hard connected to an exhaust system where the fan is
generally separate from the exhaust fans of the facility ventilation system. The
exhaust air must be double HEPA-filtered
or HEPA-filtered and incinerated.
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14. BSC Class III
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16. BSC
class
Face
velocit
y
Air flow Pattern applications
Nonvolatile
Toxic
Chemicals
and
Radionuclid
es
Volatile
Toxic
Chemicals
and
Radionuclid
es
I 75 In at front through HEPA to the
outside or into the room through
HEPA (Figure 2)
YES When
exhausted
outdoors1,2
II A1 75 70% recirculated to the cabinet
work area through HEPA; 30%
balance can be exhausted
through HEPA back into the
room or to outside through a
canopy unit (Figure 3)
YES NO (MINUTE
AMOUNT)
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17. BSC CLASS FACE
VELO
CITY
AIR FLOW PATTERN NON
VOLA
TILE
VOL
ATIL
E
II,B1 100 30% recirculated, 70% exhausted.
Exhaust cabinet air must pass
through a dedicated duct to the
outside through a HEPA filter
(Figures 5A, 5B)
YES YES
I,B2 100 No recirculation; total exhaust to the
outside through a HEPA filter (Figure
6)
YES YES
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18. II,A2 100 Similar to II, A1, but has 100 Ifm
intake air velocity and plenums
are under negative pressure to
room; exhaust air can be ducted
to the outside through a canopy
unit (Figure 7)
YES When
exhausted
outdoors
(FORMALLY
“B3”) (minute
amounts)
III N/A Supply air is HELP filtered.
Exhaust air passes through two
HEPA filters in series and is
exhausted to the outside via a
hard connection (Figure 8)
YES YES
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19. Figure 11. A typical layout for working “clean to dirty” within a Class II BSC.
Clean cultures (left) can be inoculated (center); contaminated pipettes can
be discarded in the shallow pan and other contaminated materials can be
placed in the biohazard bag (right). This arrangement is reversed for left-
handed persons.
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