Biological safety cabinets (BSCs) are enclosed, ventilated workspaces used in laboratories. They are engineered to protect the user, the work product, and the environment from hazardous biological materials. This protection is achieved through specialized airflow patterns and high-efficiency particulate air (HEPA) filters.
Choosing the correct BSC is critical for lab safety and research integrity. The decision depends on the specific biological agents, chemicals, and procedures used in your lab. Understanding the differences between the biological safety cabinet classes is the first step toward a safer, more compliant facility.
Key Takeaways
- Class I cabinets protect the user and the environment but not the product inside. They are for low-to-moderate risk agents where sterility is not needed.
- Class II cabinets protect the user, product, and environment. They are the most common type, with subtypes (A2, B1, B2) for different chemical use scenarios.
- Class III cabinets provide the highest level of containment. They are fully sealed gas-tight enclosures for work with high-risk BSL-4 agents.
Class I Biological Safety Cabinets
A Class I BSC is the simplest type of cabinet. Its primary function is to protect the user and the surrounding lab environment from hazardous aerosols generated during a procedure.
The airflow is straightforward. Room air is drawn into the cabinet through the front opening, flows across the work surface, and is then exhausted through a HEPA filter. This inward airflow prevents contaminated air from escaping the cabinet.
However, a Class I cabinet offers no product protection. Unfiltered room air constantly flows over the samples. This makes it unsuitable for work that requires a sterile environment, such as cell culture. What Class I protects is the operator, making it useful for enclosing equipment like centrifuges or for procedures with low-risk agents where sterility is not a concern.
Class II Biological Safety Cabinets
alt=’A lab technician carefully pipettes a sample inside a well-lit Class II A2 biological safety cabinet with the sash closed.’
Class II cabinets are the most common type of BSC found in clinical and research labs. They provide protection for the user, the product, and the environment. This three-way protection makes them the workhorse for most biological research.
These cabinets create an air curtain at the front opening to protect the operator. At the same time, HEPA-filtered air flows downward over the work surface to protect the samples from contamination. All exhausted air is also HEPA-filtered to protect the environment. There are several subtypes of Class II cabinets, with A2 and B2 being the most common. The main difference lies in how they handle airflow and chemical vapors. Our popular Airstream biological safety cabinet line includes these advanced options.
Class II, Type A2
The Class II A2 airflow and applications are suited for most standard microbiological work. In a Type A2 cabinet, about 70% of the air is recirculated back into the work area through a HEPA filter. The other 30% is exhausted through another HEPA filter, either back into the lab or through a thimble connection to the building’s exhaust system.
These cabinets are designed for work with biological agents in the absence of volatile or toxic chemicals. Only trace amounts of chemicals can be used, as the recirculated air could expose the user to chemical fumes.
Class II, Type B2
A Type B2 cabinet is often called a “total exhaust” cabinet. It is hard-ducted directly to an external exhaust system and vents 100% of the air outside after HEPA filtration. No air is recirculated within the cabinet or the lab.
This design makes it the proper choice when a B2 cabinet makes sense: for work involving both biological agents and significant amounts of hazardous or volatile chemicals. The total exhaust system ensures that no chemical vapors are returned to the workspace, protecting the user. Understanding the differences between a BSC and a chemical fume hood is key to making this distinction.
Class III Biological Safety Cabinets
alt=’A user manipulates materials inside a sealed Class III glovebox, wearing heavy-duty arm-length gloves attached to the unit.’
For work with the highest-risk pathogens (Biosafety Level 4), a Class III cabinet is required. These units provide the maximum level of containment. A Class III BSC is a completely sealed, gas-tight enclosure maintained under negative pressure.
The operator works through heavy-duty gloves attached to ports on the cabinet, providing Class III glovebox level containment. This creates a total physical barrier between the user and the hazardous agent. All air entering the cabinet is HEPA-filtered, and all exhausted air passes through two HEPA filters in series before being discharged outside. This design is similar to a glovebox fume hood but is built specifically for biological hazards.
Comparison of Biological Safety Cabinet Classes
This table provides a side-by-side comparison of the key features, applications, and considerations for each BSC class.
| Feature | Class I | Class II, Type A2 | Class II, Type B2 | Class III |
|---|---|---|---|---|
| Airflow Pattern | Inward flow, no recirculation. | 70% recirculated, 30% exhausted. | 0% recirculated, 100% exhausted. | Sealed system under negative pressure. |
| Product Protection | No | Yes | Yes | Yes (Maximum) |
| Personnel Protection | Yes | Yes | Yes | Yes (Maximum) |
| Typical CFM & Filtration | Single HEPA on exhaust. CFM varies. | HEPA on supply and exhaust. Thimble option. | HEPA on supply and exhaust. Hard ducted. | Double HEPA on exhaust. Hard ducted. |
| Best Applications | Housing equipment, procedures with non-sterile agents. | Cell culture, microbiology with no volatile chemicals. | Work with biologicals and volatile toxic chemicals. | Work with BSL-4 agents (e.g., Ebola virus). |
| Considerations | Does not protect the sample from contamination. | Not for use with significant amounts of chemicals. | Requires dedicated building exhaust system. | Complex setup, limited user mobility. |
How to Choose the Right BSC Class: A 5-Step Checklist
Selecting the right BSC is a critical safety decision. Follow this step-by-step checklist to ensure your choice aligns with your lab’s specific needs.
- Assess Biological Risk: First, identify the Biosafety Level (BSL) of every agent you will handle. BSL-1 agents require basic containment, while BSL-4 agents demand a Class III cabinet. This assessment is the foundation of your decision.
- Determine Need for Product Protection: Next, decide if your work requires a sterile environment. If you are working with cell cultures or other sensitive materials, you need product protection. This immediately rules out Class I cabinets.
- Evaluate Chemical Use: Then, list all chemicals you plan to use inside the cabinet. If your protocol involves volatile toxic chemicals or radionuclides, a Class II, Type A2 cabinet is not appropriate. You must select a Class II, Type B2 or Class III cabinet.
- Review Facility Requirements: After that, analyze your lab’s infrastructure. Does your HVAC system support the exhaust requirements of a ducted B2 cabinet? Confirm available space, power, and utility connections before making a purchase.
- Consult with EHS and Biosafety Officer: Finally, always consult with your institution’s Environmental Health and Safety (EHS) department. They must review and approve your choice to ensure it meets all safety regulations and institutional policies.
5 Common Scenarios for Selecting a BSC
- Scenario 1: University Cell Culture Core Facility.
- Workflow: Researchers work with non-infectious human and animal cell lines (BSL-2). No volatile chemicals are used.
- Decision: A Class II, Type A2 cabinet is the standard choice. It provides the necessary product protection to prevent contamination and protects users from potential biohazards.
- Scenario 2: Clinical Microbiology Lab.
- Workflow: Technicians identify bacterial and fungal cultures from patient samples (BSL-2).
- Decision: A Class II, Type A2 is also ideal here. It protects staff from infectious aerosols and maintains the sterility of the cultures.
- Scenario 3: Pharmaceutical Quality Control Lab.
- Workflow: A procedure requires handling a BSL-2 agent while using small, defined quantities of a volatile solvent like methanol.
- Decision: This workflow requires a Class II, Type B2 cabinet. The total exhaust system is necessary to protect the operator from inhaling chemical fumes.
- Scenario 4: Animal Research Facility.
- Workflow: Staff are changing cages for rodents housed in a BSL-2 containment suite. The goal is to contain allergens and potential pathogens.
- Decision: A Class I cabinet is often used for this task. Product protection is not needed, but personnel and environmental protection from allergens and aerosols are crucial.
- Scenario 5: High-Containment Government Lab.
- Workflow: Scientists are researching emerging infectious viruses like Ebola or Marburg (BSL-4).
- Decision: This work mandates a Class III cabinet. The gas-tight, sealed environment provides the absolute highest level of protection against deadly pathogens.
Installation, Maintenance, and Certification
Proper installation is essential for a BSC to function correctly. The cabinet must be placed away from high-traffic areas, doors, and air vents to avoid disrupting its protective air curtain. Ducted cabinets, like the Class II B2, require professional integration with the building’s HVAC system. Casework, benches, and service utilities must be planned to ensure ergonomic access and safe operation.
Regular maintenance and certification are mandatory. A certified technician must test and verify the cabinet’s performance at least annually. This includes checking airflow velocities, HEPA filter integrity, and alarm functions. Keeping detailed records is a critical part of lab compliance. Following a proper BSC certification and annual testing schedule ensures the cabinet provides consistent protection.
Frequently Asked Questions (FAQs)
1. What is the main difference between a Class I and Class II BSC?
The main difference is product protection. A Class I BSC protects the user but not the sample. A Class II BSC protects the user, the sample, and the environment.
2. Can I use a Bunsen burner inside a BSC?
It is strongly discouraged. The open flame disrupts the cabinet’s internal airflow, which can compromise both user and product protection. The heat can also damage the HEPA filters.
3. How often do HEPA filters need to be changed?
HEPA filters typically last for several years but should be changed based on the results of annual certification tests. A technician will perform a test to determine if the filter has become too loaded with particles to maintain proper airflow.
4. What is the difference between a HEPA and a ULPA filter?
A HEPA filter is at least 99.97% efficient at removing particles of 0.3 microns. An ULPA (Ultra-Low Particulate Air) filter is even more efficient, removing 99.999% of particles 0.12 microns in size. ULPA filters are often used in Class III cabinets or cleanrooms.
5. What does BSC certification involve?
Certification is a series of tests performed by a qualified technician to verify that a BSC is working correctly. It includes measuring airflow velocity, checking for HEPA filter leaks, and ensuring alarms are functional. It should be done upon installation and at least once a year after that.
6. Do I need a Class II A2 or B2 cabinet?
Choose a Type A2 if you only work with biological agents. Choose a Type B2 if your work involves both biological agents and more than trace amounts of volatile toxic chemicals. Always confirm with your safety officer.
Find the Right Biological Safety Cabinet for Your Lab
Choosing the correct biological safety cabinet class is a fundamental step in designing a safe and efficient laboratory. By carefully assessing your biological agents, chemical use, and facility capabilities, you can select a unit that provides the right level of protection for your team and your research. Each class, from I to III, is engineered for a specific set of risks and applications.
At Labs USA, we provide a wide selection of lab furniture, workstations, and containment solutions to meet your needs. Our team can help you navigate the options and plan a layout that works for you.
Explore our full range of biological safety cabinets to compare models and find the best fit for your facility.
Ready to take the next step? Request a quote today to get pricing and check current availability on our quick-ship options.
