LABORATORY SAFETY CABINET
Dr Fadhl Alakwa
http://fadhl-alakwa.weebly.com/
BIOLOGICAL SAFETY CABINET USES
Biological Safety
Cabinets offer protection
from microbiological
contamination in the
laboratory environment,
including both operator
and product protection.
 Application:
pharmaceutical, medical,
clinical research, defense,
education and general
healthcare sectors.
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BIOLOGICAL SAFETY CABINET NAMES
microbiological safety
cabinet. Other
frequently used
names include safety
cabinet, bio-safety
cabinet, biological
cabinet and laboratory
safety cabinet.
 clean rooms, laminar
flow equipment and
fume extraction
systems.

BIOLOGICAL SAFETY CABINET CLASSES
There are several
different main types of
Biological Cabinet,
specified by purpose
and construction.
 There are three main
classes of Biological
Safety Cabinet.
 Class 3 cabinets offer
the greatest
protection.

Class 1 Biological
Safety Cabinet
 Class 2 Biological
Safety Cabinet
 Class 3 Biological
Safety Cabinet

CLASS 1 BIOLOGICAL SAFETY CABINET
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A Biological Safety Cabinet
with a working front aperture
through which the user can
carry out manipulations inside
the cabinet.
It offers operator protection via
inward airflow allowing the
escape of airborne particles
generated within the cabinet
with the aid of HEPA filtration
of the exhaust air.
This type of Biological Safety
Cabinet is suitable for work
with all types of biological
agent, except Hazard Group 4.
Class I Cabinets offers
protection for the user but no
protection for the work.
CLASS 2 BIOLOGICAL SAFETY CABINET
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A Class 2 Biological Safety
Cabinet has a front aperture
through which the operator can
carry out work inside the cabinet.
Notably, it provides both worker
and materials protection.
Class 2 Biological Safety
Cabinets are the most in use biocontainment devices protecting
worker, product and environment
from potentially dangerous
microbiological agents.
A Class 2 Biological Safety
Cabinet is designed to control
airborne contamination of the
work and reduce risks of
exposure of the operator to any
airborne particles dispersed
within the cabinet from the work
procedures.
CLASS 2 BIOLOGICAL SAFETY CABINET
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The process is controlled by recirculating filtered air over the
work area combined with inflow air
passed through the working
aperture.
The escape of airborne particles
generated within the cabinet is
controlled by means of an inward
airflow at the front of the cabinet
which is filtered before circulation
within it, while the downflow
filtered air over the working surface
protects the work.
While both Class 2 Biological
Cabinets provide additional
protection to the work in the case of
both the Class 1 and Class 2 type of
safety cabinet the pattern of air
flow through the working aperture
can be disturbed by sudden
movements by the operator or
around the cabinet. Class 3
Cabinets provide greater protection
still.
CLASS 3 BIOLOGICAL SAFETY CABINET
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Class 3 Microbiological Safety
Cabinets provide total barrier
protection for the operator and are
suitable for extreme bio-hazard
work. Inflow air is HEPA filtered
before entering the Class 3
Biological Safety Cabinet via a side
mounted inlet filter chamber.
Exhaust air is HEPA filtered
before leaving the safety cabinet via
a single or double HEPA filter,
dependent on the customer’s
specific technical requirements.
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Total enclosure of the working area
User separated from the work by a
physical barrier
Filtered air continuously supplied to
the safety cabinet
Exhaust air treated to prevent
contamination
Creates total protection for user and
materials
CLASS 3 BIOLOGICAL SAFETY CABINET
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Manipulations within
the Class 3 Biological
Safety Cabinet are
carried out via gloves
mechanically attached
to the cabinet providing
a total seal against any
particulate
contamination released
within the main
working area.
Only Class 3 cabinets
which are totally
enclosed units are
suitable for work with
Group 4 hazards.
MICROBIOLOGICAL HAZARD GROUPS AND
SAFETY CABINETS
Hazard Group 1

Bio agents unlikely to
cause disease
Containment Level 1

Can be handled on an open
bench with no containment
or clean air technology
required.
Hazard Group 2

May cause disease but a low
hazard with the spread of
disease unlikely and with
prophylaxis/treatment
available.
Containment Level 2

Could be handled on an open
bench but aerosol emissions
will require containment, i.e.
in a Biological Safety Cabinet.
MICROBIOLOGICAL HAZARD GROUPS AND
SAFETY CABINETS
Hazard Group 3

Possibility of a severe
disease with spread of
disease possible although
prophylaxis/treatment is
available.
Containment Level 3

Should be handled in a
Biological Safety Cabinet.
Hazard Group 4

Causes severe disease with
serious bio-hazard risk and a
high risk of spread of disease.
With prophylaxis/treatment not
normally available this is the
most serious bio-hazard risk
group.
Containment Level 4

Must be handled in the
maximum bio-containment
facility, i.e. a Class 3
Biological Safety Cabinet.
BIOLOGICAL SAFETY CABINET TESTING
Microbiological Safety Cabinets must be
designed, sited, installed and operated in
accordance with Standards and should be
maintained in efficient working order, and
managed by a suitably qualified person who
adheres to the importance of regular containment
and filter integrity tests.
 It is a legal requirement that Biological Safety
Cabinets receive ongoing testing to ensure their
effectiveness is not compromised.
 This includes examining HEPA filters and
ensuring performance and containment criteria
are met.
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BIOLOGICAL SAFETY CABINET TESTING

A certificate of testing
must be kept clearly
visible on each
cabinet. Inspection
reports should also be
made readily
available for
inspection by
enforcing authorities
BIOLOGICAL SAFETY CABINET STANDARDS
BS EN 12469:2000
 BS 5726:2005
 BS EN 61010-1, BS
EN 292-1 and BS EN
292-2.
 NSF/ANSI standard
49
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HOW HEPA FILTERS WORK IN
BIOSAFETY CABINETS
An essential component in any clean bench or
biosafety cabinet is the high efficiency particulate
air filter, commonly called a HEPA filter.
 The HEPA filter removes particulates (generally
called aerosols) such as micro-organisms, from
the air. The HEPA filter does not remove vapors
or gases.
 HEPA filters used in clean benches and biosafety
cabinets should have a minimum
filtration efficiency of 99.99% against airborne
particles 0.3 microns in size.
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COMPONENTS OF A HEPA FILTER
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HEPA filters are made
of boron silicate
microfibers formed into
a flat sheet by a process
similar to making
paper. Flat filter sheets
are pleated to increase
the overall surface
area.
Pleats are separated by
aluminum baffles which
direct the airflow
through the
filter. Filter media is
very delicate and should
never be touched.
HOW A HEPA FILTER OPERATES:
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A HEPA filter is designed to target very small
particles, and therefore doesn’t work like a
typical membrane filter, where particles larger
than a given pore size of a filter are
captured. Instead, HEPA filters rely on a
combination of three mechanisms to trap
particles.
HOW A HEPA FILTER
OPERATES:INTERCEPTION
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where particles being
carried in the airflow
around the filter
fibers adhere to the
filter. Particles must
be within one radius
of the filter fiber to be
captured.
HOW A HEPA FILTER
OPERATES:IMPACTION
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Larger particles are
often captured by the
second mechanism,
impaction. Due to
their size, these
particles cannot
adjust to sudden
changes in airflow
around the filter and
essentially run into
the filter fiber and
become embedded.
HOW A HEPA FILTER OPERATES:
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The final mechanism is
diffusion that occurs because of
the way microscopic particles
move and interact with
surrounding molecules.
This is described as Brownian
motion, where molecules move
in a random, zig-zag pattern
because they collide with
surrounding molecules.
This motion slows down a
particle’s path through the
HEPA filter and increases the
probability that the particle
will be captured by either
interception or impaction.
HEPA FILTER EFFECTIVENESS
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The ability of a HEPA filter to remove particles
depends of the size and velocity of the particles.
Due to the mechanisms mentioned above, a HEPA
filter does not remove particles only ABOVE a certain
size. It can effectively remove particles both above
AND below 0.3 microns.
In general, large particles (greater than 0.3 microns
in diameter) are captured by both the impaction and
interception mechanisms, whereas small particles
(less than 0.1 micron in diameter) are captured by the
diffusion mechanism.
Medium particles (from 0.1 to 0.4 microns in
diameter) are captured by both the diffusion and
interception mechanisms. The most penetrating
particle size is 0.3 microns.
HEPA FILTER MAINTENANCE
As the cabinet operates, the HEPA filter will
collect particulates. The room and cabinet
particulate levels along with the capacity of the
building exhaust fan determines the life of a
HEPA filter.
 Under most laboratory conditions, you should
expect a long filter life. However, misuse or a
heavy particulate load within the cabinet will
shorten any filter's life.
 When the cabinet can no longer maintain proper
airflow balance due to the loading of the filters,
they will need to be replaced.
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REFERENCES
http://www.phac-aspc.gc.ca/publicat/lbg-ldmbl04/ch9-eng.php
 http://www.nsf.org/services/by-industry/pharmabiotech/biosafety-cabinetry/
 http://www.biologicalsafetycabinet.co.uk/
 http://info.bakerco.com/blog/bid/252645/HowHEPA-Filters-Work-in-Clean-Benches-andBiosafety-Cabinets
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