Which of the following is a common feature of all biosafety cabinets quizlet?

There are multiple biological safety cabinet classes. But what are they and how are they different? Biological safety cabinet classes (or biosafety cabinet classes) are categories describing how the cabinet works and what it protects. These “categories” are Class I, Class II and Class III. Sometimes the different cabinets are simply referred to tissue culture hoods or laminar flow hoods, and several classes can cross various applications.

Class I

A Class I cabinet is defined as a ventilated cabinet for personnel and environmental protection. Class I cabinets do not offer product protection from contamination, limiting their use in some life science applications. Class I BSCs pull room air through the front, away from the operator and have a similar airflow pattern to a fume hood, but they also have a HEPA filter at the exhaust outlet. They may or may not be ducted outside. Class I cabinets are safe for use with agents requiring Biosafety Level 1, 2, 3 or 4 containment.

Class II

A Class II cabinet iis defined as a ventilated cabinet for personnel, product and environmental protection for microbiological work or sterile pharmacy compounding. In laboratories, these hoods are often referred to as cell culture or tissue culture hoods. In pharmacy settings, these hoods are often referred to as chemo hoods. Class II BSCs are designed with an open front with inward airflow (personnel protection), downward HEPA-filtered laminar airflow (product protection) and HEPA-filtered exhaust air (environmental protection). These cabinets are further differentiated by types based on construction, airflow and how they interface with exhaust systems. The types include A1, A2, B1, B2 and C1. All Class II BSCs require all biologically contaminated ducts and plenums to be under negative pressure or surrounded by negative pressure ducts and plenums. Type B2 cabinets take this a step further, requiring all biologically contaminated ducts and plenums to be under negative pressure or surrounded by directly exhausted negative pressure ducts and plenums. Type C1 cabinets provide additional safety by maintaining protection from biological and chemical hazards during building exhaust failure. Like Class I cabinets, Class II cabinets are safe for work using agents requiring Biosafety Level 1, 2, 3 or 4 containment.

Type A1 and Type A2

A Class II, Type A1 cabinet must maintain a minimum average inflow velocity of 75 fpm through the sash opening. They may exhaust HEPA-filtered air back into the lab or may be exhaust outside using a canopy connection. They are suitable for work using biological agents without volatile toxic chemicals and volatile radionuclides. Type A1 cabinets have overwhelmingly been replaced by Type A2 cabinets over the last few decades.

A Class II, Type A2 cabinet must maintain a minimum average inflow velocity of 100 fpm through the sash opening. Like Type A1 cabinets, they may exhaust HEPA-filtered air back into the laboratory, or may be exhausted outside using a canopy connection when handling odorous samples or minute quantities of chemicals. They may also be used with tracer quantities of radionuclides that won’t interfere with the work if recirculated in the downflow air. Type A2 BSCs are the most common Class II cabinet.

 

Type B1

A Class II, Type B1 cabinet must maintain a minimum average inflow velocity of 100 fpm through the sash opening. They have HEPA-filtered downflow air composed mostly of uncontaminated recirculated inflow air and exhaust most of the contaminated downflow air through a dedicated duct that exhausts outside after passing through a HEPA filter. Like Type A2 cabinets, Type B1 cabinets are safe for work involving agents treated with minute quantities of toxic chemicals and tracer amounts of radionuclides if the chemicals or radionuclides won’t interfere with the work if recirculated in the downflow air. Unlike a Type A2, a Type B1 cabinet is also suitable for work involving minute quantities of toxic chemicals and tracer amounts of radionuclides required as an adjunct to microbiology applications, as long as the work is done in the rear portion of the cabinet behind the smoke split. The rear portion is not marked or well-defined, and is ever-changing as the BSC’s filters load, making this type of cabinet unsafe for all but the most well-trained users.

 

Type B2

A Class II, Type B2 cabinet must maintain a minimum average inflow velocity of 100 fpm through the sash opening. They have HEPA-filtered downflow air drawn from the lab or the outside air (not recirculated from the cabinet exhaust) and exhaust all inflow and downflow air to the atmosphere after filtration through a HEPA filter without recirculation in the cabinet or return to the lab. Because of this, they are sometimes referred to as 100% Exhaust or Total Exhaust cabinets. Type B2 cabinets are suitable for work involving biological agents treated with hazardous chemicals and radionuclides required as an adjunct to microbiology applications. Although Type B2 BSCs offer protection when using higher volumes of chemicals within the cabinet, they require complicated exhaust configurations and consume large amounts of air to function. As a result, Type B2 cabinets have the highest installation and operational costs of any Class II BSC.

 

Type C1

A Class II, Type C1 cabinet must maintain a minimum average inflow velocity of 100 fpm through the sash opening. Type C1 cabinets are unique in that they can operate as either a Type A cabinet when in recirculating mode or a Type B cabinet when exhausting. C1 cabinets can be changed from one mode to the other by connecting or disconnecting the exhaust and having the cabinet recertified. When in exhausted Type B mode, Type C1 cabinets clearly define the areas where users can work safely using delineated areas for storage, and a central work area with dedicated direct exhaust for use with chemical vapors, radionuclides, or chemotherapy preparations.

Class III

A Class III cabinet is defined as a totally enclosed, ventilated cabinet with leak-tight construction and attached rubber gloves for performing operations in the cabinet. The cabinet has a transfer chamber with interlocked doors that allow for sterilization of materials before entering/exiting the glove box. The cabinet is maintained under negative pressure and supply air is drawn in through HEPA filters. The exhaust air is treated with either double HEPA filtration or single HEPA filtration followed by incineration. Class III cabinets are safe for work requiring Biosafety Level 1, 2, 3 or 4 containment.

 

If you have questions about the biosafety cabinet class or type your application requires, please contact a Labconco Application Specialist.

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