Biological Safety Cabinets (BSCs)- Classes with Examples

Biological safety cabinets (BSCs) are enclosed, ventilated laboratory workspaces for safely working with materials that are or may be contaminated with pathogens requiring a defined biosafety level. BSCs provide different levels of protection for the personnel, the product, and the environment, depending on their design and operation. BSCs are classified into three classes: Class I, Class II, and Class III.

BSCs are essential equipment for many laboratories that handle biological agents, such as clinical, life science, pharmaceutical, and research laboratories. BSCs can prevent exposure to infectious aerosols and splashes that may occur during microbiological manipulations. BSCs can also maintain the sterility of the materials inside by filtering the air supply and preventing cross-contamination.

BSCs are different from laminar flow cabinets, which only provide product protection by blowing unfiltered air towards the user. BSCs are also different from fume hoods, which only provide environmental protection by exhausting air without filtering it. BSCs use high-efficiency particulate air (HEPA) filters to remove 99.97% of particles of 0.3 microns or larger from the air entering and exiting the cabinet.

BSCs require proper installation, certification, maintenance, and operation to ensure their optimal performance and safety. BSCs also require good work practices and procedures to avoid disrupting the airflow and creating hazards. BSCs should be used in conjunction with other biosafety measures, such as personal protective equipment (PPE), standard precautions, and biosafety guidelines.

In this article, we will discuss the classes of BSCs, their features and uses, their operating procedures, their applications, their advantages and limitations, and their precautions. We will also provide some examples of BSCs from different manufacturers.

Biological safety cabinets (BSCs) are specialized equipment that provide protection for personnel, environment, and product or samples when working with biohazardous materials. BSCs use high efficiency particulate air (HEPA) filters to remove airborne contaminants from the air stream and create a clean and safe work area. BSCs are classified into three classes according to their design, performance, and applications: Class I, Class II, and Class III .

• A Class I BSC is the simplest and most basic type of BSC that provides protection for personnel and environment, but not for product or samples .
• It has an open front with negative pressure ventilation that draws room air into the cabinet and exhausts it through a HEPA filter .
• The exhaust air can be either ducted to the building exhaust system or recirculated back into the laboratory after filtration .
• A Class I BSC does not prevent contamination of the sample being manipulated, as the incoming air is not filtered .
• A Class I BSC can be used for handling biological material from Risk Groups 1, 2, and 3 (RG1, RG2, and RG3), but not for research materials that require sterile conditions .
• A Class I BSC can be used for low- and moderate-risk microbiological studies, such as cage dumping, aerating cultures, fermenters, centrifuge housing, etc. .

• A Class II BSC provides protection for personnel, environment, and product or samples .
• It has an open front with an air barrier created by an airfoil and a supply aperture that prevents escape of contaminants from the cabinet .
• It uses laminar (unidirectional) airflow to filter the air supply to the internal work area and exhausts it through a HEPA filter .
• A Class II BSC can be used for handling biological material from Risk Groups 1, 2, 3, and 4 (RG1, RG2, RG3, and RG4), depending on the type of cabinet and the level of containment required .
• A Class II BSC is the most common type of BSC used in clinical, life science, pharmaceutical, and research laboratories that work with tissue culture or infectious agents .
• A Class II BSC is further divided into five types based on their construction, ventilation, and exhaust systems: Type A1, Type A2, Type B1, Type B2, and Type C1 . The main differences between these types are:

• A Class III BSC provides the highest level of protection for personnel, environment, and product or samples .
• It is a completely sealed and enclosed cabinet that is gas-tight and aerosol-tight .
• It uses supply and exhaust HEPA filters to ensure clean air inside the cabinet and prevent release of contaminants outside the cabinet .
• It has heavy-duty rubber gloves attached to the front ports that allow manipulation of the sample inside the cabinet .
• It has a negative pressure interior that is maintained by a dedicated exhaust system located outside the cabinet .
• It may have a double-door autoclave or a pass-through box that can be sterilized for transferring materials in or out of the cabinet .

• A Class III BSC is designed for handling hazardous agents that require Biosafety Level 4 (BSL-4) containment, such as emerging diseases or highly contagious pathogens

• Work from clean to dirty to minimize cross-contamination. Start with sterile or clean items and move towards contaminated or dirty items as you proceed with your work. Do not move items back and forth across the work area unnecessarily.

• One person at a time should work in a cabinet. If two people need to work in a BSC, use a 6’ cabinet and document the protocol-driven need in a risk assessment completed by the Lab Supervisor prior to starting work. Working with another person in a BSC can compromise the airflow and protection of both users, as well as increase the risk of contamination or accidents.

• Move your arms slowly in and out of the BSC. Do not move arms in sweeping, sideways movements. Rapid or lateral movements can disrupt the airflow and compromise the safety of the BSC.

• If using the vacuum system, protect the vacuum line with a filter. The filter will prevent any contaminants from entering the vacuum system or being released into the environment. Replace the filter regularly according to your laboratory SOPs.

• Do not use open flame without approval from the Safety Office. Open flame can damage the HEPA filters, create turbulence in the airflow, and pose a fire hazard. Use alternative methods such as electric incinerators, sterile disposable loops, or microburners whenever possible.

• Adjust the stool/bench height so your face is above the bottom of the sash and your arms enter the cabinet with elbows at 90° angles, armpits level with the bottom of the sash. Use a footrest if your feet do not touch the floor. This will ensure proper posture and comfort while working in a BSC, as well as optimal protection from the inward airflow.

• Discard all waste in a biohazard bag inside of a BSC. Do not remove any waste materials from a BSC until they are properly decontaminated and sealed in a biohazard bag or container. This will prevent any contaminants from escaping a BSC and reaching a user or a environment.

After Completing Work in a BSC:

• Do NOT turn blower motor OFF while removing items and decontaminating a cabinet. Keep a blower motor ON until all items are removed and all surfaces are disinfected according to your laboratory SOPs. This will maintain a inward airflow and protection of a BSC during cleanup.

• Close and surface decontaminate ALL containers and lab materials before removal. Use an appropriate disinfectant to spray or wipe all containers and lab materials that were used in a BSC before taking them out of a cabinet. This will prevent cross-contamination between different areas or experiments.

• Surface decontaminate a exterior of a biohazard waste bag/container before removal and disposal. Use an appropriate disinfectant to spray or wipe a exterior of a biohazard waste bag/container that contains any waste materials generated in a BSC before taking it out of a cabinet and disposing it according to your laboratory SOPs. This will prevent any contaminants from escaping a waste bag/container and reaching a user or a environment.

• Decontaminate cabinet interior, including sidewalls, back wall, inside of sash and work surface. Use an appropriate disinfectant to spray or wipe all interior surfaces of a BSC after removing all items and waste materials

  Examples of Biological Safety Cabinets from different manufacturers

There are many manufacturers of biological safety cabinets (BSCs) in the market, offering a variety of models and features to suit different applications and needs. Here are some examples of BSCs from different manufacturers:

• Thermo Fisher Scientific (US): Thermo Fisher Scientific is one of the global leading companies in the BSC market, offering a portfolio of BSCs that deliver reliable protection to people, products and the environment, while affording users with decades of manufacturing experience and innovations in laboratory equipment design. Thermo Scientific BSCs employ advanced airflow design, ergonomic features, cloud-based connectivity, energy efficiency and safety automation to improve the user experience and laboratory efficiency. Some of their BSC models include:

  • Thermo Scientific Herasafe 2030i: A Class II Type A2 BSC that features a smart touchscreen interface, an adaptive airflow system, a UV disinfection cycle and a remote monitoring app.
  • Thermo Scientific MSC-Advantage: A Class II Type A2 BSC that features a large work area, an easy-to-clean design, a low noise level and a low energy consumption.
  • Thermo Scientific Safe 2020: A Class II Type B2 BSC that features a total exhaust system, a dual-DC motor technology, a large sash opening and a low profile design.

• Esco Micro (Singapore): Esco Micro is one of the world`s leading providers of BSCs, with over 40 years of experience in designing and manufacturing contamination control equipment. Esco Micro BSCs are designed to meet the highest standards of quality, performance and safety, and are certified by various international agencies. Some of their BSC models include:

  • Esco Labculture Reliant: A Class II Type A2 BSC that features an angled front design, a dynamic chamber plenum, an isocide antimicrobial coating and an optional sentinel microprocessor controller.
  • Esco Airstream: A Class II Type A2 BSC that features an ultra-slim design, a night setback mode, an ergonomic armrest and an optional IV bar with hooks.
  • Esco Streamline: A Class II Type B2 BSC that features a total exhaust system, a negative pressure plenum, a bag-in bag-out filter replacement system and an optional sentinel gold microprocessor controller.

• Labconco (US): Labconco is one of the US leading manufacturers of BSCs, with over 90 years of experience in creating laboratory equipment. Labconco BSCs are designed to provide superior protection, comfort and convenience for the users, and are certified by NSF International. Some of their BSC models include:

  • Labconco Purifier Logic+: A Class II Type A2 BSC that features an LCD display, an airflow monitor, a UV light timer and a night setback mode.
  • Labconco Purifier Cell Logic+: A Class II Type A2 BSC that features a Scope-Ready package, a telescoping base stand, an intrinsically-safe negative pressure valve and a service fixture package.
  • Labconco Purifier Axiom: A Class II Type C1 BSC that features a convertible sash, a Chem-Zone work area, an exhaust canopy and a myLogic operating system.

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