What is Biocabinet purpose, What is biocabinet containment, Why biocabinets

What is Biocabinet purpose speaks to what is biocabinet containment and why biocabinets in a laboratory.

When properly maintained and used in conjunction with good laboratory techniques, Biocabinets (BSCs) provide effective primary containment for work with human pathogens.

In containment level 2 facilities, biocabinets are used for procedures with the potential to produce infectious aerosols and for high concentrations or large volumes of infectious material.

In containment levels 3 and 4, all open vessel activities with infectious materials are conducted in a BSC.

Biocabinets Training

Every employee working in a biocabinets must be trained in its correct use and have a good understanding of the different types of cabinets and how they work. Detailed information on the selection, function, and use of biocabinets can be found elsewhere in the literature.

Classes and Characteristics of Biological Safety Cabinets

There are three classes of biocabinets: Class I, Class II and Class III. Selection of the proper class of BSC requires careful evaluation of the activities to be carried out.

Horizontal, clean benches that direct air towards the operator are not biological safety cabinets and must not be used for handling infectious, toxic or sensitizing materials. Only cabinets that meet the National Sanitation Foundation (NSF) Standard No. 49-2002 (independent standard for the design, manufacture and testing of BSCs) and bear an NSF 49 seal should be purchased.

Class I Cabinets

These cabinets have unrecirculated airflow away from the operator that is discharged to the atmosphere after filtration through a HEPA filter. They provide good operator protection but do not protect the material within the cabinet (the product) from contamination.

Class II Cabinets

Class II cabinets are designed for personnel, product and environmental protection. They are designed for work involving microorganisms in containment levels 2, 3 and 4 laboratories and are divided into two types (A and B) on the basis of construction type, airflow velocities and patterns, and exhaust systems.

Within type (A), there are two subtypes, A1 (formerly designated type A) and A2 (formerly designated type B3). Within type (B), there are two subtypes, B1 and B2. Class II cabinets are most commonly used in biomedical research laboratories because of their characteristics.

Class II, Type A1 Cabinets

Cabinet air may be recirculated back into the laboratory or ducted out of the building by means of a "thimble" connection (i.e., a small opening around the cabinet exhaust filter housing) whereby the balance of the cabinet is not disturbed by fluctuations in the building exhaust system.

The thimble must be designed to allow for proper certification of the cabinet (i.e., provide access to permit scan testing of the HEPA filter).

  • Maintain a minimum average face velocity of 0.38 m/s (75 ft/min).
  • May have positive pressure contaminated ducts and plenums.
  • Are not suitable for work with low levels of volatile toxic chemicals and volatile radionuclides. Class II, Type A2 Biocabinets Cabinet air may be recirculated back into the laboratory or ducted out of the building by means of a "thimble" connection (i.e., a small opening around the cabinet exhaust filter housing) whereby the balance of the cabinet is not disturbed by fluctuations in the building exhaust system. The thimble must be designed to allow for proper certification of the cabinet (i.e., provide access to permit scan testing of the HEPA filter).
  • Maintain a minimum average face velocity of 0.5 m/s (100 ft/min).
  • Have ducts and plenums under negative pressure.
  • Is suitable for work with minute quantities of volatile toxic chemicals and trace amounts of radionuclides. Class II, Type B1 Cabinets Hard-ducted through a dedicated duct exhausted to the atmosphere after passage through a HEPA filter; contain negative pressure plena.
  • Maintain a minimum average face velocity of 0.5 m/s (100 ft/min).
  • Recirculate 30% of the air within the cabinet.
  • Suitable for work with low levels of volatile toxic chemicals and trace amounts of radionuclides. Class II, Type B2 Cabinets
  • Does not recirculate air within the cabinet.
  • Maintain a minimum average face velocity of 0.5 m/s (100 ft/min).
  • Hard-ducted through a dedicated duct exhausted to the atmosphere, 100% of cabinet air, after passage through a HEPA filter; contain negative pressure plena.
  • Suitable for work with volatile toxic chemicals and radionuclides. The exhaust canopy must allow for proper BSC certification. An alarm should be provided that is audible at the cabinet to indicate loss of exhaust flow from the building exhaust system. The cabinet internal fan should also be interlocked to shut down when the building exhaust system fan fails, to prevent pressurization of the cabinet. Class III Cabinets Class III cabinets are totally enclosed and gas-tight with HEPA filtered supply and exhaust air. Work is performed with attached long-sleeved gloves. The cabinet is kept under negative pressure of at least 120 Pa (0.5 in. w.g.), and airflow is maintained by a dedicated exterior exhaust system. Class III cabinets protect the worker and the product. They are designed for work with level 4 pathogens and provide an alternative to the positive-pressure suit made for maximum containment laboratories. Cabinet lines consisting of several Class III cabinets (e.g., for centrifuges, animal cages, incubators, refrigerators) and transfer devices joined together are traditionally custom built. Specific guidance on the unique requirements for constructing, installing, certifying and using Class III cabinet lines can be found elsewhere(5-7). The exhaust air is double HEPA filtered or treated by HEPA filter and incineration. Removal of materials from the cabinet must be through a dunk tank, double door autoclave or air-lock pass-through for decontamination. Interlock or protocols must be used for the autoclave and pass-through doors to prevent both doors from being open at the same time.
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