LAMINAR FLOW HOODS & BIOLOGICAL SAFETY CABINETS
What are HEPA (High Efficiency Particulate Air) filters?
They consist of a thin pleated sheet of boron silicate microfibres with aluminum separators
They are particulate filters which retain airborne particles and microorganisms (gases pass
freely through)
Filtration occurs by five distinct methods (*primary mechanisms):
1) sedimentation
2) electrostatic attraction
3) interception*
4) inertial impaction* and
5) diffusion*
How are HEPA filters rated?
HEPA filters are rated on their ability to retain particles of around 0.3 microns in size
tested with PAO (poly alpha olefin) which produces particles of 0.26 microns in size
most aerosol droplets are greater than 0.26 microns
Do you know the difference between a laminar flow hood and a biological safety
cabinet?
Laminar Flow Hoods
provide product protection only and must not be used when working with any form of
biohazard or chemical hazard
any potentially infectious aerosol that is created will lead to exposure of the operator and the
environment
horizontal-flow clean-air bench used for cell cultures can expose the researcher to aerosols of
allergenic or infectious materials.
vertical-flow clean-air bench also blows air out into the room
Biological Safety Cabinets
provide personnel and environment protection and usually product protection
infectious agents must be used in a biological safety cabinet NOT a laminar flow hood
Do you know the difference between Class I, II & III Biological Safety Cabinets?
Class I Biological Safety Cabinet:
a ventilated cabinet which provides personnel and environmental protection only
air flow is directed away from the researcher, but is not HEPA filtered, therefore there is no
product protection
similar to a fume hood with a HEPA filter on the exhaust system to protect against the
release of biohazards
inward air flow ranges from 75 125 linear feet per minute (lfpm)
can be used with radioisotopes and some toxic chemicals
Class II Biological Safety Cabinet:
provides personnel, product and environmental protection
there are supply air and exhaust air HEPA filters
two general types: IIA cabinets have a minimum inward air flow of 75 fpm and recirculates
70% of the air; IIB cabinets have a minimum inward air flow of 100 fpm and exhaust either
70% (type B1) or 100% (type B2)
most of the biological safety cabinets at UVic are Class II
Class III Biological Safety Cabinet:
these cabinets provide personnel, product and environmental protection
they are hermetically sealed and all procedures are conducted through arm-length rubber
gloves
used in high level (Level 4) containment labs
there are two HEPA filters on the exhaust system
Are you sure you are using your Biological Safety Cabinet correctly?
the cabinet must be turned on at least 5 minutes before starting work in order to purge the air
and remove any particulates
the researcher should wear a closed-front lab coat (or surgical gown) and gloves
the gloves should overlap the cuffs
all materials needed for the manipulations should be placed in the cabinet before the work is
initiated to minimize in-and-out motions
do not cover the air intake grill
the researcher should work well into the cabinet and not out close to the front (at least four
inches from the front grill)
when in use, the entry door to the lab (particularly in small rooms) must be kept closed and
traffic minimized
do not have electric fans blowing in the room when the biological safety cabinet is in use
this will seriously effect the air flow of the unit
develop procedures for the collection and decontamination of waste materials to avoid clutter
and minimize in-and-out motions
the cabinet must be decontaminated with an appropriate disinfectant at the end of each work
operation
periodic use of 1-10% household bleach in water is acceptable, but chlorine is corrosive
(70% ethanol or quaternary ammonium compounds may also be used if effective against
agent)
all biological safety cabinets must be certified for use when first installed, any time the
unit is moved or repaired, and on an annual basis
all cabinets will have a certification sticker indicating the last date of testing on the front face
of the cabinet
For further information on the use, testing or selection of biological safety cabinets please
contact Occupational Health, Safety and Environment at local 8971.
Occupational Health, Safety & Environment
Rev. May 10, 2011
