The Difference Between Animal Handling Biosafety Cabinets and Animal Transfer Stations

Operation & Design Fundamentals of Animal Handling Biosafety Cabinets and Animal Transfer Stations (ATSs) to Ensure Safety in Vivarium.

To maintain the safety of both lab personnel and the animals they are working with, it is crucial that only purpose-built equipment is used. This precaution is important due to potential contaminants spreading to the animals in the vivarium. Certain measures must be taken to remove contaminants within vivarium applications. Staff members wearing PPE (personal protection equipment) as well as other safety measures are all important. Knowing the individual needs of your staff members and applications are also important. Implementing proper measures can help save resources and research if the correct equipment is being used. This is why it is important to understand the use and differences of Animal Handling Biosafety Cabinets and Animal Transfer Stations.

HEPA Filtration Requirements

Although they appear similar, there are many differences between Animal Handling Biosafety Cabinets and Animal Transfer Stations. Both of these cabinets are designed to have a vertical laminar down flow of air. The air must be HEPA-filtered (high-efficiency particulate air filter) within the animal containment area. The National Sanitation Foundation (NSF) standards indicate that Class II BSC’s are required to have HEPA filters that have a minimum efficiency of 99.99% for particles sized 0.3 microns for both the outflow and inflow of air. To extend the life of HEPA filters, washable mesh pre-filters are often employed. These types of filters will capture larger particles such as hair, dust, and dander before they reach the main HEPA filter.

While both Animal Handling Biosafety Cabinets and Animal Transfer Stations are designed with similar airflow, there are major differences in their intended purposes due to their construction and methods of operation. Lets dive into the main differences.

What are Animal Handling Biosafety Cabinets (BSC)?

Animal Handling Biosafety Cabinets offer a safe, controlled environment for handling materials and other hazardous items. These cabinets need the level of a Class II BioSafet Cabinet. This will allow personnel to safely perform tasks within the workspace such as examination, injections, and manipulation of the test subject.

Currently there are three classifications of biosafety cabinets: class I, class II and class III. Each class offers a higher range of biocontainment as necessary.

• Class I BSC’s are designed to redirect ambient air past the cabinet user and through the work area. This type of airflow will protect personnel and the surrounding environment.
• Class II BSC’s offers a mid-range protection that is designed to protect personnel and the surrounding environment like Class I. The difference is Class II also adds protection for the product(s) being worked on.
• Class III BSC’s offers the highest protection level for biocontainment. These cabinets provide access to the workstation by physical barriers. The physical barrier involves a completely enclosed workspace that is accessed through gloves that are built into the cabinet. This prevents any decontamination and fully protects the user and surrounding environment.

Within the Class II biosafety cabinets classification, there are various sub categories. These sub categories depend on the need for the air passing through the workspace to be either exhausted or recirculated. Animal Handling Biosafety Cabinets are structured for the specific needs of the researchers using them. Custom designs allow for the addition of pre-filters, waste-chutes that are built-in and pass-through chambers for cages. Class II animal handling biosafety cabinets allow for the protection of animals that are potentially immunocompromised, infectious, or carrying an unknown biohazard.

Performance Standards for Biosafety Cabinets

Guidelines for the design of biosafety cabinets are primarily outlined by the performance standards of NSF/ANSI 49 or EN 12469. These standards help regulate the function of BSC’s such as the dynamic air flow (downflow and inflow velocity), acceptable sash heights, exhaust system parameters and biocontainment limits. They also suggest (but do not require) the use of pre-filters in conjunction with HEPA filters.

You should also consider the necessity for recertification of the unit if it is relocated or moved within the vivarium. An airflow smoke pattern test must be performed each time the BSC is used in a new area. If the cabinet is moved to a new facility and was subjected to excessive vibrations a recertification test is imperative to determine if the cabinet will still provide the appropriate level of containment needed.

To observe with regulatory agency specifications, biosafety cabinets must undergo periodic recalibration and certification. This involves sustaining the standard inflow and downflow velocities dictated by the NSF:

• Class II BSCs should maintain a minimum inflow velocity of 100 fpm (0.51 m/s)
• Downflow velocity requirements vary by model, with most falling between 50 to 80 fpm (0.25 to 0.40 m/s) for both types.
• Class II, Type A2 BSC models exhaust roughly 30% of the air passing through the workspace and recirculate the remaining 70%
• Class II, Type B1 cabinets have the opposite configuration of A2 models, exhausting 70% and recirculating 30% of the air passing through the workspace.
• Class II, Type B2, and Class III biosafety cabinets exhaust 100% of the air passing through the workspace.

Animal Transfer Stations (ATS) and their Performance Standards

Animal Transfer Stations (ATS) provide a controlled air workstation for moving animal cages when the animal is non-infectious. They are used to maneuver animals between soiled and clean cages. Typically they are not intended for actual testing uses such as injections or examinations. These units are not designed to provide any protection against hazardous or infectious agents. They will, however, provide some protection against most allergens.

Despite there not being any performance standards required by an establishment, the certification of these units may be required to align with manufacturer specifications.

The design and functionality of an ATS can vary greatly due to the lack of a regulatory body. Commonly, a “push-pull” airflow is employed. This means the air flow moves from top to bottom by an upper air supply impeller. A motor underneath then pulls the air through slots along the edge of the workspace. ATS workspaces can be accessed from either one or both sides depending on the need. Although the dual sided access stations provide more convenience, the single sided access stations provide a heartier air barrier. While having a smaller footprint, ATSs have a larger sash opening. This allows for simple mobility of larger cages in and out of the workspace. The easy maneuverability and adaptability of an ATS makes it acceptable for a wide range of uses that do not need a higher level of containment in vivarium settings.

Performance of Animal Transfer Stations

Without having any oversight from regulators, individual manufacturers have established their own set of criteria for the performance of animal transfer stations. For instance, single-sided units protection against allergens through an air barrier at the front of the workstation. Dual sided units operate with what is a called an air piston. Both units use an airflow pattern where air is pulled from the top of the device through a HEPA filter. The air then passes through the workstation where an additional HEPA filter is used. Once the air passes through the second filter, it is then recirculated back out into the vivarium. It is crucial to be in communication with your chosen ATS manufacturer as the air flow velocity varies widely depending on the manufacturer. Doing this will assure your workstation meets your specific needs.

Summary

Despite the similarities of Animal Handling Biosafety Cabinets and Animal Transfer Stations the level of protection is vastly different. Animal Transfer Stations will not provide the level of protection needed to perform procedures such as, biopsies, examinations or other invasive research. However, an Animal Handling Biosafety Cabinet would be excessive and inconvenient for needs that do not require biocontainment. As well as working with a manufacturer to assure you are purchasing the correct workstation suited to your labs specific needs, it is also extremely important to have any lab workers be properly training on safety practices and having your workstation recertified on a consistent basis.

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