What is a Laboratory Biological Safety Cabinet?

Everything You Need to Know About Laboratory Biological Safety Cabinets

A laboratory biological safety cabinet (BSC), also referred to as a biosafety cabinet, is one of the most crucial pieces of safety equipment in laboratories. It is the fundamental engineering control used to protect workers and equipment in laboratories against biohazards or infectious agents. Additionally, it helps to check and maintain quality control of the agents being worked with as it filters both exhaust and inflow air. At times, it is interchangeably known as a laminar flow or tissue culture hood.

The safety cabinet is designed and engineered to protect against infectious or biohazardous splashes, particulates, or aerosols. They are mostly generated while handling materials containing biohazardous agents, including diagnostic specimens, primary cultures, and stocks. Some amount of air in the majority of BSCs is re-circulated back into the laboratory because of the exhaust HEPA (high-efficiency particulate air) filter. Although this clears the air, it does not reduce the exposure to infectious chemicals or animal dander.

These processes should be carried out in a way that lowers the production of aerosolized material and prevents spills. Procedures like sonication, centrifugation, vortexing, and opening the containers of biohazardous chemicals whose internal pressure differs from the ambient pressure are known as aerosol-producing procedures. By all means, they should be conducted inside the cabinet, or additional measures must be taken to elevate the safety.

What is a Safety Cabinet Used For?

As mentioned above, a safety cabinet is one of the most important pieces of equipment in labs. It uses laminar airflow and HEPA filtration to block aerosols produced during the handling of biological materials.

Given below are some of the major uses of a laboratory safety cabinet:

  • It offers protection for the lab environment from chemicals within the safety cabinet.
  • It protects lab workers from infectious or biohazardous chemicals used inside the cabinet.
  • It protects the sample from contamination.

What are the Three Class Types of Biosafety Cabinets?

BSCs are categorized into three classes depending on their containment capabilities when handling biological chemicals.

Class 1 Biosafety Cabinets

The Class 1 BSC offers personal and environmental protection against infectious chemicals and powders. Air enters the BSC through the frontal aperture passing from an inbuilt exhaust fan called the HEPA filter, thereby providing both the personnel and the environment protection against biohazardous agents. This air then leaves the BSC at the back of the work surface.

In case any airborne particulates are generated within the biosafety cabinet, their escape is controlled by means of the inward airflow via the frontal aperture and by absorption of the exhausted air. The HEPA filter provides environmental protection by filtering air before it escapes.

These cabinets are not applicable for handling research chemicals prone to airborne contamination. This is because the inflow of the unfiltered air from the lab can draw biohazardous contaminants into the BSC. In such cases, a BSC Class 2 is more appropriate.

Class 2 Biosafety Cabinet

The Class 2 biosafety cabinet offers personnel, environmental, and product protection against infectious agents. The inward flow of air passes into the work chamber through the frontal aperture and the worktop. It also has a back plenum, wherein 70% of air is re-circulated through the primary HEPA filter to the work area as downflow, and 30% of air is exhausted. It provides personnel protection via inflow, product protection via downflow, and environmental protection through the filtered exhaust.

The HEPA filter guarantees the elimination of any cross contamination since the air in the work area has to re-circulate through two sets of primary HEPA filters. This kind of BSC is appropriate for handling biohazardous chemicals such as category 3 pathogens, cytostatics, and virus manipulation.

Types of Class 2 Biosafety Cabinets

There are two kinds of Class 2 biosafety cabinets (Type A and Type B) based on their build and configuration. They are categorized based on the percentage of air exhausted to that of air re-circulated. Moreover, these cabinets have different kinds of exhaust, wherein some portion of the exhaust air may directly circulate in the laboratory, while the other portion heads back to an external ventilation system.

Type A cabinets are appropriate for research in microbiology without the use of any toxic chemicals as air is re-circulated within the cabinet. Type B cabinets are hard-ducted to the main exhaust system and include a negative pressure plenum.

Class 3 Biosafety Cabinet

A Class 3 Biosafety Cabinet, also referred to as a Glovebox, is aerosol-tight equipment with no openings and has a tightly sealed front window, which separates the worker from the cabinet through a physical barrier. An operator has to wear long heavy-duty rubber gloves that are attached to the ports in the front of the BSC tightly. This prevents cross containment and also allows access to the cabinet.

Materials from Class 3 cabinets must be removed through a safety airlock transfer hatch or double door autoclave, which can be found on the father end of the cabinet for decontamination. Several measures need to be taken for the autoclave and hatches to prevent both of them from being open at the same time.

Class 3 cabinets are applicable for work with chemicals assigned to levels 1, 2, 3, and 4. They are used for work with highly biohazard agents, where maximum protection and safety are needed. Examples include Ebola and all kinds of agents with risks of transmission.

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