Biological Safety Cabinets

Biological safety cabinets, or BSCs, are enclosed, ventilated hoods or workspaces that allow for the safe handling of pathogens, contaminants, and other potentially hazardous materials.

These types of equipment are also referred to as biosafety cabinets or microbiological safety cabinets. When outfitted with glove systems (in the case of Class III biosafety cabinets), they are also called gloveboxes.

The primary purpose of a biosafety cabinet is to protect the operator and the surrounding environment from biological contaminants and other hazardous materials. There are various classes of biological safety cabinets, each defined by the required level of biosafety and containment as well as the required configuration of the cabinetry. The proper class and type is selected in accordance with the requirements for the specific application and level of bio-containment needed.

Classes and Types of Biological Safety Cabinets (BSC)

BSCs in the U.S., and in many countries, are officially designated and described in the Biosafety in Microbiological and Biomedical Laboratories (BMBL) 5th Edition. This biological safety manual is produced by the U.S. Centers for Disease Control and Prevention (CDC) and the National Institutes of Health (NIH). According to the BMBL, biological safety cabinets are designated as follows:

Class I Biological Safety Cabinet

Class I BSCs provide personnel and environmental protection, but do not provide product protection. The Class I BSC is similar in terms of air movement to a chemical fume hood. However, unlike a chemical fume hood, the Class I BSC has a HEPA filtration system that handles the air exiting the unit, providing protection for the environment.

Class II Biological Safety Cabinet

Class II hoods provide personnel, environmental, and product protection for a range of low- to moderate-risk materials. These biological safety cabinets are used in research, clinical, industrial, and pharmacy settings.

With Class II cabinets, airflow is drawn into the front grille of the unit, providing personnel protection. In addition, the downward flow of HEPA-filtered air provides product protection by minimizing the chance of cross-contamination across the work surface of the hood. Exhaust air is passed through a certified HEPA filter to provide particulate filtration to protect the environment.

For Class II, Type A1 and A2 BSCs, exhaust air may be recirculated to the laboratory or, alternatively, it may be discharged from the building via a canopy, or “thimble,” connected to the building’s exhaust. CDC regulation standards require exhaust air for Class II, Types B1 and B2 BSCs be discharged directly to the outdoors via a hard connection.

These hoods are commonly used in the hospital pharmacy, in addition to a wide range of clinical and research applications.

Class III Biological Safety Cabinet

Class III cabinets are utilized for working with highly infectious microbiological agents and for the conduct of hazardous operations. This class provides maximum protection for both the worker and the environment.

The Class III BSC is a gas-tight enclosure with a non-opening view window. Access for passage of materials into the cabinet is through a dunk tank, which is accessible through the cabinet floor, or through a double-door pass-through box (e.g., an autoclave sterilizer) that can be decontaminated between uses. Reversing the process allows materials to be safely removed from the cabinet. Gloves are attached to the unit, utilizing gas-tight ports, to allow users to directly manipulate the materials inside the cabinet.

Both the supply and exhaust air of the Class III BSC are stringently HEPA filtered. The air that is exhausted from the unit must pass through two HEPA filters or through a HEPA-filtration in combination with an air incinerator before the air is discharged directly outdoors. CDC regulation standards require that Class III BSCs do not discharge air through the general laboratory exhaust system.

Class III BSC units may be joined together to implement a larger capacity containment area.

Biosafety Cabinets Compared to Standard Clean Benches

Biosafety cabinets (BSCs) should not be confused with clean air workbenches or standard laminar flow workstations. Standard horizontal or vertical laminar flow clean benches are not equivalent to BSCs.

In a standard laminar flow clean bench, HEPA filtration and positive pressure air is used to protect the product, but not the worker. A basic biological safety cabinet’s primary purpose is to protect both the worker and the environment from hazards within the cabinet, but not necessarily the product. The Class I BSC is not designed for product protection.

Class II and III BSCs are designed to protect the product along with the worker and environment. The appropriate class and type of BSC is selected according to specific regulatory requirements for product protection, worker protection, and environmental protection.

Germfree manufactures a wide range of Biological Safety Cabinets that are utilized for applications within the fields of healthcare, research, security, and industry. Germfree units include Class I and Class II BSCs and Class III BSC gloveboxes to allow for the safe handling of potentially hazardous agents as well as for the sterile preparation of materials. Visit our Biological Safety Cabinets page to learn more.

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