Primary containment represents the procedures and practices and equipment used to prevent the dissemination of research materials from the location where the are being used.

Secondary containment consists of the laboratory or facility where the work takes place. It includes all of the elements that prevent research materials from entering the environment, inadvertently . Emphasis is usually placed on the primary means of containment which are provided by laboratory practices and containment equipment. 

Laboratory practice and technique are the most important elements of primary containment.

Persons working with infectious agents or infected materials must be aware of potential hazards and be trained and proficient in the practices and techniques required for handling such material safely. 

The supervisor is responsible for providing or arranging for appropriate training of personnel.  Individuals who have specific concerns or questions regarding established protocols should ask their supervisor or EHS.

The selection and use of primary barriers is dictated by the hazard potential of the biological system.

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.

SECONDARY CONTAINMENT

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 environment.

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.