Biological safety cabinets (BSCs) are essential in laboratory environments where work involves potentially hazardous materials. They provide a controlled environment to protect personnel and the laboratory setting from exposure to pathogens, ensuring a safe working space. There are several types of BSCs, each differentiated by the level of biocontainment they provide to meet the requirements of specific biosafety levels.
This article will explore different classes of biological safety cabinets, their unique features, and their applications in various laboratory settings. Understanding how to select the right BSC and justify its usage is crucial for maintaining safety standards and ensuring regulatory compliance in laboratory operations.
What Is a Biological Safety Cabinet (BSC)?
Biohazard is an infectious agent or parts thereof, that presents a real or possible hazard to the health of not only humans but also plants and animals. Biohazards are categorized by risk groups that correlate to biosafety level standards (BSL 1-4). These typically refer to the Biological Safety Cabinet.
The best source of operational guidance comes from your institution. The Centre for Disease Control will give you the requirements when working with agents or samples that you have in the laboratory. In addition, your institution may require additional compliance. Outside the USA, another guideline is the WHO Biosafety Manual.
Understanding why Biological Safety Cabinets are required when working with biohazard samples is essential. Laboratory Fume Hoods are generally inappropriate for containing biohazards, which would be dispersed into the environment and still bioactive.
Class II BSC has HEPA filters that protect personnel, products, and the environment. The air in these cabinets can circulate to the lab or be exhausted outside.
A biological safety cabinet (BSC) or microbiological safety cabinet is an enclosed, ventilated laboratory workspace for safely working with materials contaminated with (or potentially contaminated with) pathogens requiring a defined biosafety level. Several different types of BSC exist, differentiated by the degree of biocontainment they provide.
Safety cabinets must be certified periodically for their efficiency. Various field tests are performed to verify air flows, HEPA filter integrity, and containment of contaminated cabinet air.
BSC aims to protect personnel and the environment. Мany of BSCs should maintain the sterility of testing products.
Classification of BSC
The U.S. Centers for Disease Control and Prevention (CDC) classifies BSCs into three classes.
BSC Class I
Class I cabinets provide personnel and environmental protection but no product protection. The air passes upwards through a high-efficiency particulate air (HEPA) filter before being exhausted. Biosafety Level 1 is for undergraduate and secondary educational training and teaching laboratories and for other laboratories that use nonpathogenic microorganisms.
Examples are Bacillus subtilis, Naegleria gruberi, and infectious canine Hepatitis virus. Thus, BSL-1 containment only requires a sink for hand washing.
BSC Class II
Class II and Class III biological safety cabinets provide personnel, environmental, and product protection.
Class II BSCs are open-fronted enclosures, similar to Class I BSCs, in which the air enters the cabinet through the front opening to provide operator protection.
Biosafety Level 2 is appropriate for clinical, diagnostic, teaching, and other laboratories that deal with indigenous moderate-risk agents linked with human disease and are present in a community. Examples are the Hepatitis B virus, HIV, Salmonella, and Toxoplasma. These microorganisms may be used on the open bench if aerosol production is low.
Types of Class II Cabinets
There are four types (A1, A2, B1, B2 and C1) of Class II BSCs. The main differences between the types are the ratio of air exhausted from the BSC to the air recirculated within the BSC and the type of exhaust system present.
To understand how BSCs work, we need to understand how they are built. The main components include the blower and plenum, the work area, and controls. The upper area has HEPA filters and a negative pressure design.
The work area is made of stainless steel, dished work surface, and fixtures that provide easy access to tubing into the BSC. The control part can be located above the user area or at the line of sight for easy access.
Principles of operation use fans mounted in the cabinet to draw directional mass airflow around a user and into the air grille – protecting the operator. The air is drawn underneath the work surface and back up to the top of the cabinet, passing through the HEPA filters.
A column of HEPA-filtered, sterile air is also blown downward over products and processes to prevent contamination. Air is also exhausted through a HEPA filter, and depending on the type of Class II BSC, the air is either recirculated back into the laboratory or pulled by an exhaust fan through ductwork, where it is expelled from the building.
Types A1 and A2 Cabinets (Class II BSC)
The Type A1 cabinet, formerly known as Type A, has a minimum inflow velocity of 75 ft/min. The downflow air, considered contaminated, splits just above the work surface (the BSCs smoke split) and mixes with the inflow. This air is drawn, through ductwork, up the back of the cabinet, which is then blown into a positive pressure, contaminated plenum.
The Type A2 cabinet, formerly designated A/B3, has a minimum inflow velocity of 100 ft/min. All contaminated positive-pressure plenums are surrounded by a negative air pressure plenum. In other respects, the specifications are identical to those of a Type A1 cabinet.
Class II Type A2 Safety Cabinets are often selected for applications for microbiology, cell culture, clinical research, healthcare, and life science research. They help ensure excellent protection of personnel, environment, and product protection, as well as protection from cross-contamination.
Types B1 and B2 Cabinets (Class II BSC)
In contrast to the type A1 and A2 cabinets, Type B BSCs use single-pass airflow (air that does not mix and recirculate) also to control hazardous chemical vapors. Type B1 and B2 cabinets have a minimum inflow velocity of 100 ft/min, and these cabinets must be hard ducted to an exhaust system rather than exhausted through a thimble connection.
The Type B2 cabinet (also known as a Total Exhaust BSC) is expensive to operate because no air is recirculated within. Therefore, this type is mainly found in such applications as toxicology laboratories, where the ability to use hazardous chemistry safely is important.
Additionally, if the exhaust system for a Type B1 or B2 cabinet were to fail, contaminated air could flow into the laboratory. To mitigate this risk, cabinets of these types generally monitor exhaust flow, shutting off the supply blower and sounding an alarm if the flow is insufficient.
Type A2 and C1 cabinets can circulate air back to the lab or exhaust the air outside. Software, performance, and ergonomics are the main elements that impact BSC, and the newer designs improve sustainability, longevity, and safety.
For example, advanced designs (type C1) reduce overall exhaust air, and robust motors increase HEPA filter life. Cabinets are certified to the version of the standard they were designed to. A 20-year-old cabinet is certified to a 20-year-old standard. Newer units are designed to current design standards.
Class II cabinets provide the most advanced features and innovative technology like smart protection, ergonomics, ease of use, smart cleaning, and disinfection.
Additionally, the standard USB data has embedded capability to provide cloud-based connectivity. This enables customers to check the BSC status in real time and be alerted to critical issues via alarms and alerts. Maintenance requirements and the ability to interrogate the events log are also available.
Latest Class II BSC Types
Recent versions of Class II BSC (MSC-Advantage BSC) combine safety, energy efficiency, and value for today’s laboratory.
The advantages of these cabinets are:
- SmartPort convenience
- SmartClean windows design
- LED control panel
The MSC-Advantage biological safety cabinet is suitable for all applications where personnel, environmental, and product protection is required, as well as protection from cross-contamination. Typical applications are routine research applications in cell culture, clinical research, life science research, and microbiology.
Cytotoxic Cabinets
Cytotoxic cabinets help ensure excellent protection when handling cytotoxic substances. They have a triple filter design for better filtration efficiency than regular class II biological safety cabinets.
Digital Airflow Verification (DAVe) alerts, system self-checks, and performance status are provided on the full-color touchscreen. Furthermore, with enabled connectivity, the remote app provides all the data a technician needs. Routine maintenance, cleaning, and setup tasks in these cabinets are simplified.
Cytostatic safety cabinets are often selected for applications for work with hazardous drugs, CMR (carcinogenic, mutagenic, reprotoxic) substances, including preparation of hazardous drugs in healthcare compounding pharmacies and facilities complying with USP or other specialized procedures, particularly in Europe.
Class III Biological Safety Cabinets
The Class III cabinet, generally only installed in maximum-containment laboratories, is specifically designed to provide maximum protection when working with BSL-4 pathogenic agents.
The enclosure is gas-tight; all materials enter and leave through a dunk tank or double-door autoclave. Gloves attached to the front prevent direct contact with hazardous materials.
Interesting fact: Class III cabinets are sometimes called glove boxes.
Class III BSCs are typically fitted with a pass box (often independently ventilated) or dunk tank to facilitate the movement of potentially contaminated work materials in and out of the cabinet. An autoclave may also be attached for waste management, mainly in facilities with a maximum containment cabinet line.
Clean Benches
Clean benches provide a clean (aseptic) space to work with a product or specimen without contaminating it with particles such as microorganisms. They protect the product; they do not protect the user or the environment. Clean benches meet ISO class 5 minimum conditions achieved in the work area and EU GMP Grade A work environment.
They have many advantages, like Smart Ports, side windows, and intuitive control panels.
Typical applications for clean benches are:
- Hospitals (Pharmacy) – drug dispensing, IV mixture prep, media prep, drug compounding
- Hospitals (microbiology dept.) – Tissue Culture (nonbiological)
- IVF departments
- Pharmaceutical research
- Cleanrooms – GMP suites
- Pharmaceutical Microbiology
- Sterile packaging and filling
- Microelectronics assembly and semiconductor production
- Plant cell culture/agriculture
- Food and drink industry
- Cosmetics industry
- Aerospace industry
FAQ
What Are the Main Differences Between a Biosafety Cabinet and a Laminar Flow Clean Bench?
Biosafety cabinets protect the user, environment, and product, while laminar flow clean benches only protect the product from contamination.
Related: Laminar Flow Cabinets in GMP Regulated Environments
What Is the Proper Decontamination Procedure Before Performing Maintenance on a BSC?
Before maintenance, BSCs should be decontaminated with appropriate disinfectants, such as formaldehyde or hydrogen peroxide, to ensure safety during servicing.
How Should Airflow Alarms Be Handled in a BSC?
Airflow alarms should not be ignored. Users should stop work immediately, investigate the issue, and contact maintenance to prevent unsafe exposure.
Can BSCs Be Relocated Within a Laboratory or to Another Facility?
Yes, but they must be decontaminated before moving and recertified after relocation to maintain the correct airflow and containment.
What Should Be Done if the HEPA Filter In a BSC Is Compromised?
If a HEPA filter is compromised, the BSC must be taken out of service immediately, the filter replaced by certified personnel, and the unit recertified before resuming use.
Summary
Biosafety cabinets (BSCs) are one type of biocontainment equipment used in biological laboratories to protect the operator, the laboratory environment, and experimental materials from exposure to infectious aerosols and splash when operating contagious materials such as bacterial strains, primary cultures, and diagnostic specimens.
While all three classes protect personnel and the environment, only Class II and III cabinets protect products. A BSC’s HEPA filter effectively traps infectious organisms and ensures that only microbe-free exhaust air is discharged from the cabinet.
As for biosafety cabinet application, a biosafety cabinet is widely used in scientific research, teaching, clinical testing, and production in microbiology, biomedicine, genetic engineering, and biological products.
Biosafety cabinets must be inspected by trained personnel regularly and be “certified” as safe for work involving infectious agents or toxins.
