Safety equipment includes
biological safety cabinets, safety blenders, safety centrifuge cups
and a variety of enclosed containers. These pieces of equipment, along
with proper techniques, will help to confine experimental materials
to the work area and prevent their escape via aerosols into the laboratory
or external environment.
The biological safety cabinet (BSC) is the biologists answer to
a chemical fume hood. There are three types of cabinets (Class
I, II, III) used in laboratories. Open-fronted Class I and
II BSC's are partial containment cabinets.
When used in conjunction
with good microbiological technique, they offer protection to laboratory
personnel and to the environment. Since the inward air velocities
(face velocities) are similar with both classes, they provide, generally,
an equivalent level of personnel protection. The use of Class
II cabinets offers the additional advantage of protecting materials
contained within it from extraneous airborne contaminants. This
additional protection is provided by an air barrier created by the
downward flow of HEPA filtered air within the work space and the air
intake at the front opening.
Neither of these cabinet classes (I or II) is appropriate for
the containment of the highest risk infectious agents because of
the potential inadvertent escape of aerosols across the open front.
The Class III cabinet, commonly referred to as a glove box, provides
the highest level of personnel and material protection. This
protection is provided by the physical isolation of the space in
which the infectious agent is manipulated.
When Class III cabinets are required, all procedures involving
infectious agents must be conducted within them. These cabinets
are frequently designed as a system of interconnected modules.
Each module contains a piece of the equipment required by the laboratory
program. There may be modules for incubators, a refrigerator,
centrifuge and even animal storage cages.
In general, secondary barriers are those features associated with
the facility which surround the primary barriers. These features
provide varying degrees of isolation between the laboratory and
the outside environment (as well as from other spaces in the same
building). Examples of secondary barriers are floors, walls
and ceilings, air locks and self-closing doors, differential pressures
between spaces (positive pressure and negative pressure designs
to ventilation system), exhaust filtration, as well as devices for
treating contaminated air, liquids and solids. These barriers
serve to prevent the escape of microorganisms in the event of a
failure in a primary barrier and can be designed to prevent environmental
organisms from contaminating the workspace.
The primary function
of the facility is to provide a physical environment in which work
activity can be undertaken efficiently and safely. A well-designed
facility will facilitate good laboratory practice, contain equipment
necessary to protect the worker and provide for the protection for
those outside of the laboratory or building.
Well designed facilities
primarily protect the environment and cannot be considered as a
replacement for good laboratory procedures and practices.
The best way to control
these risks is through the use of techniques and equipment designed
to contain aerosols and prevent their release to the work and general
The requirements to treat effluent air and liquid (when
necessary) to render them biologically inactive before release are
as important as the requirements to use aseptic technique.