What’s Biological Safety Cabinet (BSC)? Types and How Does It Work

Navigating the intricate realms of research and scientific inquiry requires not only knowledge and precision but also tools that can ensure safety, especially when dealing with hazardous biological agents. Enter the Biological Safety Cabinet (BSC), an unsung hero of the modern laboratory. The BSC isn’t just a workspace; it’s a meticulously engineered barrier, standing guard between researchers and potential contaminants.

But what precisely is a BSC? How does it manage to provide such a bulwark of safety? And are all BSCs created equal? In this blog, we will delve deep into the world of BSCs, exploring their types and dissecting their inner workings. Join us as we unravel the science and engineering behind these critical laboratory guardians.

What is Biological Safety Cabinet (BSC)? Definition

A Biological Safety Cabinet (BSC) is a specialized, enclosed, ventilated workspace in a laboratory designed to provide a clean work environment and protection for personnel, the experiment or product, and the surrounding environment. It achieves this through directional airflow and high-efficiency particulate air (HEPA) or ultra-low penetration air (ULPA) filtration. BSCs are essential when researchers work with infectious agents, toxic substances, or other biohazardous materials to prevent contamination and exposure.

The air inside the cabinet is either exhausted to the exterior of the building or recirculated within the laboratory after passing through filters that trap potentially hazardous particles. There are different types of BSCs, each with specific designs to accommodate various levels of biohazard containment and research requirements.

How Does Biological Safety Cabinet (BSC) Work

Benefits and Purpose Of Biological Safety Cabinet (BSC)

The Biological Safety Cabinet (BSC) plays a critical role in modern laboratories, particularly those dealing with biological samples and infectious agents. Here are the primary benefits and purposes of BSCs:

  • Protection of Personnel: The primary purpose of a BSC is to safeguard lab personnel from infectious or biohazardous agents. The cabinet does this by maintaining a constant inflow of air, preventing aerosols or droplets containing pathogens from escaping into the lab environment where they could be inhaled or come into contact with the worker.
  • Protection of the Product or Experiment: By ensuring a sterile environment inside the cabinet through HEPA or ULPA-filtered air, BSCs protect biological samples, tissue cultures, and other experiments from environmental contaminants like dust, microbes, or foreign DNA, ensuring the integrity and validity of experimental results.
  • Protection of the Environment: BSCs prevent potentially harmful agents or particles from escaping into the surrounding environment. The exhaust air from the cabinet is filtered to capture and contain biohazardous materials, ensuring that only clean air is either recirculated into the lab or released outside.
  • Containment of Aerosols and Droplets: Many laboratory procedures can produce aerosols or droplets, which could be potentially infectious. BSCs are designed to capture and contain these, preventing their spread and potential contamination.
  • Flexibility in Research: The different classes and types of BSCs offer varying levels of protection, allowing researchers to choose a suitable cabinet based on the risk level of their work. This means that a wide range of research can be safely conducted, from non-pathogenic bacteria studies to research on deadly viruses.
  • Safe Handling of Toxic and Radiolabeled Materials: While primarily designed for biohazards, some BSCs, especially Class II Type B2 cabinets, are built to handle volatile chemicals and radionuclides safely, adding versatility.
  • Ergonomic Design: Modern BSCs are designed considering the researcher’s comfort. Features like adjustable heights, armrests, and well-placed utilities make long working hours inside the cabinet less strenuous.
  • Alarms and Safety Features: Many BSCs are equipped with alarms and sensors that alert the user if the airflow is compromised, ensuring an immediate response to any potential safety breach.
  • Supports Biosecurity: In the context of global health and biosecurity, BSCs play a pivotal role in preventing the accidental release of potentially pandemic-causing pathogens, ensuring that research remains confined to a controlled environment.

In essence, Biological Safety Cabinets are indispensable in ensuring the safety and efficacy of biological research, providing an environment where scientists can confidently work, knowing that they, their experiments, and the surrounding environment are protected.

Biological Safety Cabinet (BSC) Types

Different Types Of Biological Safety Cabinet (BSC)

Biological safety cabinets (BSCs) are enclosed, ventilated laboratory workspace areas designed to protect the laboratory worker and the surrounding environment from pathogens and other hazards. BSCs are utilized when working with infectious agents, tissue cultures, and other biohazardous materials. The main types of biological safety cabinets include:

Class I BSC

The Class I Biological Safety Cabinet is the most basic type and acts primarily as a protective barrier between the user and the hazardous material inside. It achieves this by constantly drawing air away from the operator and into the cabinet. This constant inflow of air ensures that any airborne particles, including potentially harmful microbes, are drawn away from the user, reducing the risk of inhalation.

The exhaust air is passed through a high-efficiency particulate air (HEPA) filter, designed to capture 99.97% of particles 0.3 microns or larger. This ensures that pathogens or other hazardous particles are effectively trapped and the exhaust air is clean when released back into the laboratory or outside. However, since there’s no filtered air blown across the working area, the samples inside aren’t protected from contamination.

Class II BSC

Class II, Biological Safety Cabinets, offer a higher level of protection than Class I cabinets, safeguarding the user, the environment, and the samples being worked on. This is achieved through a combination of inflowing and downflowing HEPA-filtered air. The downflow creates a curtain of clean air that protects the samples from contamination.

The subtypes of Class II cabinets vary based on their construction and airflow patterns:

  • Type A1: This type recirculates a majority (70%) of the air within the cabinet while exhausting the remaining 30%. It can either be connected to an external exhaust system (hard-ducted) or recirculate the air back into the lab after filtration. This design makes it versatile but unsuitable for volatile toxic chemicals or radionuclides.
  • Type A2: Similar to A1 cabinets, A2 cabinets recirculate 70% of the air. However, they have an increased airflow, which results in a more rigorous exhaust requirement. This means they can handle slightly more hazardous materials than A1 cabinets.
  • Type B1: A significant portion of the air, more than 30%, is exhausted in B1 cabinets, with less than 70% being recirculated. This makes them more suitable for work involving minute quantities of volatile toxic chemicals, provided they are used with biological samples.
  • Type B2: These cabinets exhaust 100% of the air. With no recirculation, they are ideal for work with volatile toxic chemicals and radionuclides.
  • Type C1: This innovative design can function like an A2 or a B2 cabinet based on its configuration. The flexibility of C1 cabinets makes them adaptable for different kinds of work, from biological samples to minute amounts of chemicals.


Often referred to as a “glove box,” the Class III Biological Safety Cabinet is the epitome of containment. It is completely sealed and operates under negative pressure to ensure no unfiltered air escapes. All interactions with samples within the cabinet are done through built-in rubber gloves. This design ensures maximum protection, especially when dealing with highly pathogenic agents like Ebola. The exhaust air is rigorously filtered, often through HEPA and ultra-low penetration air (ULPA) filters, to capture even the tiniest particles.

While Biological Safety Cabinets offer varying degrees of protection, their efficiency and safety are contingent upon proper installation, usage, and maintenance. These cabinets must undergo regular certification by professionals. This ensures they function optimally and continue offering protection against potential hazards.

What is Biological Safety Cabinet (BSC)

How Does Biological Safety Cabinet Work?

A Biological Safety Cabinet (BSC) is an engineering control that provides a clean and contained environment for safely working with infectious and other hazardous materials. The working principle of a BSC is based on directing the airflow in a manner that ensures both safety and cleanliness. Here’s an overview of how a BSC works:

1. Airflow Direction

When operating a BSC, the primary concern is the management of airflow. As the BSC is turned on, it actively pulls in room air from the front opening, which is in the direction of the person operating the cabinet. This stream of incoming air acts as a frontline protective barrier. Its main role is to ensure that any aerosol or particulate matter generated within the cabinet does not escape and contaminate the external environment or pose a risk to the operator.

Simultaneously, inside the cabinet, there is a systematic downward airflow. This descends from the cabinet’s top and smoothly spreads across the work surface. This mechanism ensures that the internal work environment is continuously surrounded by clean air, minimizing cross-contamination between different samples in the cabinet.

2. HEPA/ULPA Filtration

Central to the efficacy of a BSC is its filtration system. Before any air is either recirculated or expelled, it’s subjected to rigorous filtration. The most commonly used filters are the High-Efficiency Particulate Air (HEPA) or the more refined Ultra Low Penetration Air (ULPA) filters. HEPA filters are adept at capturing 99.97% of all particles that are 0.3 microns or larger.

ULPA filters elevate this standard by capturing up to 99.999% of particles that are 0.12 microns or bigger. It’s essential to understand that it’s not just the exhausted air that gets filtered. The air directed downwards onto the work surface also undergoes filtration, ensuring the workspace remains sterile.

3. Exhaust System

BSCs are diverse in design, catering to varied research needs. Depending on its design, once the air inside has been filtered, it can either be reintroduced into the laboratory or vented out of the building. In some advanced settings, especially when the research involves volatile chemicals or substances that could pose a significant environmental hazard, BSCs can be attached to an external exhaust system. This system often incorporates added layers of filtration or treatment mechanisms, guaranteeing safety.

4. Negative Pressure Design

A noteworthy safety feature, especially prevalent in Class III cabinets, is the maintenance of a negative pressure gradient within the containment area. This design choice ensures that the cabinet’s interior always has a slightly lower pressure than the surrounding room. Such a configuration guarantees that in the event of any unintentional openings or breaches, the external room air would flow into the cabinet, preventing the escape of contaminants from the cabinet into the room.

5. Sash and Front Opening

The BSC’s front opening is where the researcher primarily interacts with the samples. This opening is protected by a movable shield known as a sash. Besides serving as a physical barrier against potential splashes or aerosol escape, the sash is essential in correctly regulating and directing the airflow.

In the case of Class III cabinets, sashes are replaced with dedicated glove ports. These ports allow researchers to handle materials inside through specially attached gloves, ensuring no direct air exchange with the external environment, maximizing containment.

6. Ultraviolet (UV) Light

A supplementary feature in some BSCs is the inclusion of UV lamps. When the cabinet is inactive, these lamps can be turned on to irradiate the internal surfaces. UV light has germicidal properties and aids in reducing the microbial load within the cabinet.

However, it’s crucial to acknowledge that UV lamps do not substitute proper cleaning and decontamination procedures. Their role is to augment cleanliness, not replace standard cleaning practices.

7. Control Systems

Modern iterations of BSCs come equipped with sophisticated electronic control systems. These systems continuously monitor parameters like airflow velocity, filter status, and overall operational efficiency. They are designed to instantly alert the user if these parameters deviate from the set standards, enabling immediate corrective actions.

A BSC harmoniously integrates directed airflow, cutting-edge filtration, and airtight containment strategies. This synergy ensures that the cabinet offers a safe and sterile environment, protecting the researcher and the external surroundings from contamination.

Biological Safety Cabinet (BSC)

How To Use Biological Safety Cabinet (BSC) Properly?

Using a Biological Safety Cabinet (BSC) properly ensures personal safety, prevents contamination, and maximizes the cabinet’s efficiency. Here’s a step-by-step guide on how to use a BSC correctly:

1. Preparation Before Use

  • Cleanliness: Start with a clean work area. Before initiating any work, disinfect the interior surfaces of the cabinet using an appropriate disinfectant (commonly 70% ethanol or isopropanol).
  • Material Arrangement: Only bring the necessary materials into the BSC. Arrange them to minimize the movement of “dirty” items over “clean” ones. This reduces the risk of cross-contamination.
  • Verify Operation: Ensure the BSC is operating correctly. Check the airflow alarm system, and ensure no obstructions in the front grill, which could compromise the protective air barrier.

2. Starting the BSC

  • Turn On: Start the BSC at least 10-15 minutes before beginning work to purge the workspace of particulates.
  • Check Alarms and Indicators: Ensure that airflow indicators show appropriate airflow levels and no alarms are sounding.

3. Working in the BSC

  • Slow Movements: When moving hands and arms in and out of the cabinet, do so slowly to prevent disrupting the airflow, which could allow contaminants to escape or enter the work zone.
  • Work at Least 4 Inches In: Perform all work at least 4 inches inside the cabinet to ensure you’re working within the clean air zone and not compromising the protective air barrier.
  • Use Proper Techniques: When using pipettes or other instruments, ensure they don’t generate splashes or aerosols.

4. Handling Materials and Equipment

  • Minimize Movement: As much as possible, try to minimize rapid or sweeping movements within the cabinet.
  • Storage: Do not store materials or equipment inside the BSC between uses. This could block vents or grills and disrupt airflow patterns.
  • Avoid Overcrowding: Do not overcrowd the workspace. Keeping it clear ensures efficient airflow and reduces the risk of contaminating materials.

5. Completing Work in the BSC

  • Decontaminate: Before removing any items from the BSC, surface-decontaminate them to reduce the risk of transferring potential contaminants from the cabinet.
  • Final Clean: Once all items are removed, clean the interior of the BSC with the appropriate disinfectant, starting from the back and moving forward. Don’t forget the walls, work surface, and any remaining equipment.
  • Turn Off the BSC: If the BSC is not being used continuously or by another person, turn off the UV light (if used) and then the blower. Remember, if using a UV light, ensure it’s only on when the cabinet is not in use.

6. Routine Maintenance

  • Regular Inspection: Frequently inspect the BSC for cracks, leaks, or other signs of wear that could compromise its function.
  • Scheduled Servicing: Adhere to regular maintenance and certification schedules. A BSC should be certified annually and any time it is moved.

7. Emergency Situations

  • In case of a spill inside the BSC, immediately cover the spill with absorbent towels to prevent aerosol generation. Then clean and disinfect the affected area.
  • If the BSC alarm sounds, stop operations to ascertain the reason. It could indicate airflow disruption, filter blockage, or other concerns.

In addition to these steps, proper training and periodic refresher courses are essential for all BSC individuals. Being attentive to the equipment’s operations, adhering to best practices, and promptly addressing any issues will ensure that the BSC provides maximum protection during use.


The Biological Safety Cabinet (BSC) stands as a testament to the intertwining of science and engineering, all in the pursuit of safety and precision in the laboratory. As we’ve journeyed through its types and intricate mechanisms, it’s evident that the BSC is more than just a piece of equipment. It’s a shield, safeguarding researchers from potential hazards while ensuring that scientific experiments remain uncontaminated and accurate.

Understanding its diverse types and specific functions is crucial for any institution or individual aiming to maintain the highest standards in research environments. As science continues to push boundaries, the BSC remains a steadfast guardian, evolving and adapting, ensuring that discovery and safety always go hand in hand.