Biosafety Cabinet: Definition, Classification (Class I, II, III), Working Mechanism, Application, Features.

A biosafety cabinet (BSC) is a piece of laboratory equipment that is used to protect the laboratory worker and the environment from exposure to potentially harmful biological materials. BSCs are designed to provide a physically and biologically contained workspace for activities such as cell culture, microbiology, and molecular biology. They typically include a ventilation system that filters the air flowing into and out of the cabinet, and a work surface that is impervious to liquids and easy to decontaminate. There are different types of biosafety cabinets, including Class I, Class II, and Class III, each designed to provide a different level of protection.

Biosafety Cabinet Definition

The biosafety cabinet (BSC) also known as the microbiological safety cabinet or biological safety cabinet, are an enclosed, and ventilated laboratory workspace that is designed to protect the laboratory worker and the surrounding environment from infectious pathogens.

The exhaust air inside the biosafety cabinet pass through a HEPA filter and removes all the hazardous agents such as viruses and bacteria.

Biosafety cabinets (BSCs) offer three levels of protection, known as Class I, Class II, and Class III. Each class of BSC is designed to provide a different level of protection, depending on the type of biological material being handled and the level of risk associated with the work being done.

1. Class I BSCs: These cabinets provide the lowest level of protection, and are primarily used for work with low-risk biological materials such as bacteria and fungi. They are also known as “exhaust BSCs” as they are designed to remove contaminants from the air inside the cabinet and exhaust them to the outside of the lab.
2. Class II BSCs: These cabinets provide intermediate level of protection and are intended for work with moderate-risk biological materials, such as viruses and human cell lines. They are also known as “recirculating BSCs” as they are designed to filter and recirculate the air inside the cabinet, rather than exhausting it to the outside.
3. Class III BSCs: These cabinets provide the highest level of protection and are intended for work with high-risk biological materials, such as pathogenic microorganisms and prions. They are also known as “total containment BSCs” as they are designed to provide a completely sealed and separate environment for the handling of extremely hazardous materials. These biosafety cabinets are generally used in high-level containment labs.

Read Also: Biosafety levels With their Primary and Secondary Barriers.

Features of Biosafety Cabinet

Biosafety cabinets (BSCs) are designed to provide a physically and biologically contained workspace for activities involving potentially harmful biological materials. Some key features of BSCs include:

1. Physical containment: BSCs are designed to physically contain biological materials and prevent them from escaping into the laboratory environment.
2. Biological containment: BSCs are equipped with HEPA filters that remove airborne contaminants from the air flowing into and out of the cabinet, providing an additional layer of protection against the release of biological materials.
3. Ventilation: BSCs have an internal ventilation system that constantly circulates filtered air to ensure that the air inside the cabinet is free of contaminants.
4. Work surface: BSCs have a work surface that is impervious to liquids and easy to decontaminate, providing a protected space for activities such as cell culture and microbiology.
5. Lighting: BSCs are designed with energy-efficient lighting that provide illumination in the cabinet.
6. Safety interlock: It has safety interlock switch which prevents the cabinet from being operated if the sash window is not closed properly.
7. Type of Biosafety Cabinet: There are different types of BSCs, including Class I, Class II, and Class III, each designed to provide a different level of protection.
8. Access port : Some BSCs have access ports for electrical or other connections to devices outside the cabinet, to make it more convenient for the user to perform experiments.
9. Large Viewing window : BSCs have large viewing window for observation of the experiments and samples inside.
10. Durable construction: BSCs are built to last, with durable construction and materials that are resistant to wear and tear.

Why should we use Biosafety Cabinets?

We should use biosafety cabinets to;

• HEPA filters and an air curtain protect personnel from biohazardous aerosols generated within the chamber.
• Recirculating and unidirectional HEPA-filtered air protects samples from contamination by contaminated laboratory air.
• HEPA-filtered exhaust from the top of the cabinet prevents biohazardous aerosols within the chamber from polluting the lab environment.

Types of Biosafety Cabinets (Classes of Biological Safety Cabinets)

There are three main classes of biological safety cabinets (BSCs) used in laboratories: Class I, Class II, and Class III. Each class of BSC is designed to provide a different level of protection to the laboratory worker and the environment, depending on the type of biological material being handled and the level of risk associated with the work.

1. Class I BSCs, also known as “exhaust BSCs” or “Type A” provide the lowest level of protection. They protect the laboratory worker and environment by drawing in air from the laboratory and passing it through a HEPA filter before expelling the filtered air outside of the laboratory. They are used for work with low-risk biological materials such as bacteria and fungi, and for tasks that do not generate a lot of aerosols or splashes.
2. Class II BSCs, also known as “recirculating BSCs” or “Type B1/B2” provide intermediate level of protection. They protect the laboratory worker and environment by recirculating air through a HEPA filter, which removes any contaminants that may be present in the cabinet. They are intended for work with moderate-risk biological materials, such as viruses and human cell lines, and for tasks that generate a moderate amount of aerosols or splashes.
3. Class III BSCs, also known as “total containment BSCs” or “Type C” provide the highest level of protection. They are intended for work with high-risk biological materials, such as pathogenic microorganisms and prions. They provide a completely sealed environment, with all of the air being HEPA filtered, both incoming and exhaust. They are used in high-level containment laboratories, and are equipped with additional safety features such as a double-door entry system and special glove ports for access to the work area.

• Class I
• Class II
  
  • Type A
    • Type A1
    • Type A2
  • Type B
    • Type B1
    • Type B2
• Class III

1. Class I Biosafety Cabinet (BSC)

• Biological Safety Cabinets (BSCs) are essential equipment in any laboratory that handles potentially harmful biological materials. They provide a physical and biological barrier that helps protect the laboratory worker and the environment from exposure to these materials. Among the different classes of BSCs, Class I BSCs are the most basic type.
• A Class I BSC provides protection to the environment and the laboratory personnel but does not provide protection to the product. The unsterilized room air is drawn over the work surface, which means that the samples are not protected from the environment. Class I BSCs are typically used to either enclose specific equipment like centrifuges or for procedures like aerating cultures that might potentially generate aerosols.
• BSCs of this class can be either ducted, which means they are connected to the building exhaust system, or unducted, which means they recirculate filtered exhaust back into the laboratory. In the Class I BSC, the room air is drawn in through the opening that also allows the entry of the operator’s arm during work. The air inside the cabinet then takes in the aerosol particles that may have been generated and moves it away from the operator towards the HEPA filter. The air moving out of the cabinet is thus, sterilized via the HEPA filters before its discharge to the environment.
• In this way, the cabinets protect the operator and the environment from the aerosol but not the sample. This means that, while the Class I BSC provides a level of protection to the laboratory worker and the environment, it is not appropriate for handling high-risk biological materials or for procedures that generate large amounts of aerosols.
• It is important to match the biosafety level of the cabinet with the work you are doing, and to consult the manufacturer or lab safety expert to ensure compliance with all applicable regulations. Proper training on the safe operation, maintenance and decontamination procedures for the BSCs, as well as knowledge of emergency procedures in case of malfunction, is also crucial.
• In conclusion, Class I Biological Safety Cabinets (BSCs) are a basic type of BSC that provide protection to the laboratory worker and the environment, but not to the product. They are suitable for procedures that might generate aerosols or to enclose specific equipment, but not for handling high-risk biological materials. They are an important tool for maintaining a safe and productive working environment, but it is important to use them appropriately, properly maintain and ensure.

Working Principle of Class I Biosafety Cabinet

The BSC is designed to protect the laboratory worker and the environment from exposure to potentially harmful biological materials by enclosing the workspace and controlling the airflow.

The airflow enters the cabinet through the front entrance at a minimum velocity of 0.38 m/s and moves over the workspace before exiting the cabinet through an exhaust duct. The stream of inward air is responsible for transporting out all the aerosols produced during the microbiological manipulation. This is an important feature of the BSC as it helps to contain any potential contaminants and prevent them from escaping into the laboratory environment.

The air is then filtered through a HEPA (High-Efficiency Particulate Air) filter and pre-filter before it is released from the cabinet. The HEPA filter captures all airborne particles and pollutants, ensuring that the air released from the cabinet is clean and contaminant-free.

Overall, the airflow system of a BSC plays a crucial role in ensuring that the cabinet provides a safe and protected environment for working with biological materials. It is important to maintain the airflow system by regularly checking and replacing the filters, to ensure that the cabinet is functioning properly.

Features of Class I Biosafety Cabinet

• Front opening
• Exhaust plenum
• Shash
• Exhaust HEPA filter.

Uses of Class I Biosafety Cabinet

A Class I Biosafety Cabinet (BSC) is a type of laboratory equipment that is used to protect the user, the samples, and the environment from biohazards. They are used in many different types of laboratory settings, including medical, research, and industrial laboratories.

Some common uses of Class I Biosafety Cabinets include:

• Handling and culturing of cell cultures and bacteria.
• Preparing and handling of samples for PCR.
• Preparing and handling of samples for microbiological assays.
• Preparing and handling of samples for serological assays.
• Handling of low-risk biological materials, such as plant and animal tissue samples.
• Handing of small volumes of hazardous chemicals.

A Class I Biosafety Cabinet provides personnel, product and environmental protection via HEPA-filtered air, which is filtered through High Efficiency Particulate Air filter to capture 99.99% of airborne particles at 0.3 microns or larger in size. It does not provide protection for operator with harmful agents, it can recirculate the air and protect only products, surrounding environment, and operator from cross contamination.

Advantages of Class I Biosafety Cabinet

• They provide protection for the user, the samples, and the environment from biohazards.
• They are relatively easy to use and maintain.
• They can be used for a wide variety of laboratory procedures.
• They are less expensive than other types of biosafety cabinets.

Disadvantages of Class I Biosafety Cabinet

• They do not provide the same level of protection as other types of biosafety cabinets, such as Class II or Class III cabinets.
• They may not be suitable for working with highly infectious or dangerous materials.
• They rely on HEPA filter which need to be replaced periodically and may be subject to filter leakage and air velocity issues.
• They may not provide enough protection if the user is handling large volumes of hazardous materials.
• They do not protect the operator but only the product, environment and samples.

It is important to note that Class I Biosafety Cabinets are not suitable for working with airborne biohazards or for procedures that generate high-level aerosols, thus need to be used with care and trained personnel. They are generally used for low-risk procedures and samples.

2. Class II Biosafety Cabinet

• A Class II Biosafety Cabinet, also known as a Biological Safety Cabinet (BSC), is a specialized laboratory equipment designed to protect people, the environment, and the product from biohazards. It is commonly used in a variety of settings such as clinical, life science, hospitals, pharmaceuticals, and research labs that handle tissue culture or infectious agents in Risk Groups 2, 3, and 4.
• Unlike Class I Biosafety Cabinets, which rely on HEPA-filtered air to recirculate and protect the samples, surrounding environment, and operator, Class II Biosafety Cabinets use a combination of negative pressure, airfoil, and HEPA filters to create an air barrier at the front of the cabinet. This barrier helps to stop air from passing through the access panel and supply aperture and reduce turbulence and cross-contamination inside the cabinet. Additionally, the laminar airflow and HEPA filtration system work together to create a clean and safe work environment for the operator.
• Another important distinction between Class I and Class II Biosafety Cabinets is the ventilation and exhaust systems. While Class I cabinets rely on recirculating air, Class II cabinets are designed to evacuate a portion of the air from the cabinet and exhaust it outside the room or facility. This helps to ensure that the environment is protected from any potential biohazards.
• Additionally, the exhaust system used in Class II cabinets can vary depending on the type, such as A1, A2, B1, B2, and C1, this will be designed according to the specific lab requirements.
• In summary, Class II Biosafety Cabinets provide a higher level of protection than Class I cabinets, by creating an air barrier, reducing turbulence and cross-contamination, and expelling a portion of the air outside the room or facility.
• They are ideal for working with tissue culture or infectious agents in Risk Groups 2, 3, and 4, and are widely used in clinical, life science, hospitals, pharmaceuticals, and research labs.

Uses of Class II Biosafety Cabinet

A Class II Biosafety Cabinet (BSC) is a ventilated laboratory workspace designed to provide personnel, environmental, and product protection for work involving agents that are assigned to Biosafety Level 1, 2, or 3. The cabinet provides a barrier between the work being done and the environment, and also filters and removes potentially contaminated air before it is exhausted. This type of cabinet is typically used for work with microorganisms, cell cultures, and materials that may contain low to moderate levels of potentially infectious agents. Some common uses of a Class II Biosafety Cabinet include:

• Handling and culturing of microorganisms, including bacteria, viruses, and fungi.
• Manipulation of biological materials such as blood, tissues, and body fluids.
• Handling of live animals, particularly for research purposes.
• Preparation of biological samples for analysis, including DNA and RNA extraction.
• Work with biological toxins and other hazardous materials.
• work with biologicals, viruses and chemical that are at risk of exposure to open air.

Advantages of Class II Biosafety Cabinet

• Provides a barrier between the worker and the biological materials being handled, reducing the risk of exposure to infectious agents or other hazardous materials.
• Filters and exhausts potentially contaminated air, reducing the risk of contamination of the laboratory or the surrounding environment.
• Provides a controlled environment for sensitive biological materials such as cell cultures or live animals.
• The cabinet allows performing manipulations of biological samples, this include experiments, analysis and measurements with reduced contamination risk.

Disadvantages of a Class II Biosafety Cabinet

• Class II Biosafety Cabinets can be expensive to purchase and maintain.
• They may require special electrical, plumbing and ventilation connections, which can be costly and need specific building modifications.
• They can be cumbersome to use, particularly for larger equipment or samples, and may require additional space in the laboratory.
• They can be noisy and may interfere with communication between workers.
• They may need regular maintenance and certification to ensure they are functioning properly
• They require special training on how to use them properly, to avoid contamination and exposure.

General Working Principle of Class II Biosafety Cabinet

The working mechanism of the Class II Biosafety cabinet is totally different from others. For personnel protection, it contains an open front with inward airflow. To protect the product from contamination it has a downward HEPA filtered laminar airflow over the work surface. To protect the environment it has HEPA filtered exhaust air.

The inward airflow enters the cabinet with a velocity of  0.38 m/s through the front opening and then it passes through a supply HEPA filter. Next, it follows the downwards over the work surface.

During the downward, it “splits” about 6–18 cm from the work surface, one-half passes through the front exhaust grill, and the second half passes through the rear exhaust grill. The generated aerosols will be captured by this downward airflow and will pass through the front or rear exhaust grills, which will provide a maximum level of product protection.

After that, the air is released into the space between the supply and exhaust filters located at the top of the cabinet. Then the supply HEPA filter recirculates 70% air within the cabinet and the remaining 30% is released into the room environment through the exhaust filter.

A. Class II Type A1 Biosafety Cabinet

• The Face Velocity is 75 fpm
• 70% air recirculated through HEPA Filter.
• 30% air Exhausted Through the HEPA Filter.
• Class II Type A1 Biosafety cabinet Cannot be used for Radio Nucleotides and Toxic Chemicals
• It is used in Biosafety Levels 2 & 3.
• Class II Type A-I Biosafety Cabinets provides personal, product, & environment Protection.

Working Principle of Class II Type A1 Biosafety Cabinet

• With a face velocity of 0.38 m/s or 75 fpm, the incoming airflow enters the cabinet through the front door, which subsequently passes through a supply HEPA filter. Afterward, it travels at a downward angle across the desk.
• At a distance of 6–18 cm from the work surface, it “splits” during the descending action, with half going through the front exhaust grill and the other half going through the rear. The produced aerosols will be gathered by this downward airflow and will travel via the front or rear exhaust grills, ensuring the best level of product protection.
• It is released into the space between the supply and exhaust filters at the top of the cabinet. The supply HEPA filter then recirculates 70% of the air inside the cabinet, while the exhaust filter expels the remaining 30% into the room. This is because modifying this ratio is impeded by the respective sizes of the two filters.
• If you’re dealing with poisonous substances or radioactive nucleotides, you can’t use it.

Class II Type A1 Biosafety Cabinet Features

• Front opening 
• Sash
• Exhaust HEPA filter
• Rear plenum 
• Supply HEPA filter
• Blower

B. Class II Type A2 Biosafety Cabinet

• Downward Velocity Is 100 fpm.
• 70% air recirculated through HEPA  Filter.
• 30% air Exhausted Through HEPA Filter.
• Type A2 Biosafety Cabinet Can be used for Radio Nucleotides and Toxic Chemicals.
• Use for Biosafety Levels 2 & 3 User.
• It provides Product, & Environment Protection.
• Under Negative Pressure to room.
• The Exhaust Air is Hard Ducted.

Working Principle of Class II Type A2 Biosafety Cabinet

• Cool air is sucked into the cabinet through the front grill. A plenum in the back wall allows air to be sucked up from under the desk by a motor blower.
• Then, after passing through a HEPA filter, the filtered air is pumped into the centre plenum from the top of the cabinet.
• The remaining 70% of air is recirculated into the work area through a HEPA filter in a laminar (unidirectional) flow pattern.
• When the fan is turned on, the air flows over the workspace, through the front airflow grill, up the back wall, and back under the workspace. It goes under and around the table as well.
• Type A2 Biosafety Cabinets are approved for use with both radio nucleotides and dangerous compounds.

Class II Type A2 Biosafety Cabinet Features

• The front opening
• Sash
• Exhaust HEPA filter
• Supply HEPA filter
• Positive pressure plenum
• Negative pressure plenum 

C. Class II Type B1 Biosafety Cabinet

• The Downward Velocity is 100 fpm.
• 30% air is recirculated through HEPA Filter.
• 70% air Exhausted Through the HEPA Filter.
• It Can be used for Radio Nucleotides and Toxic Chemicals (Low Levels / Volatility).
• It is designed for Biosafety Levels 2 & 3 Users.
• It provides Product, & Environment Protection.

Working Principle of Class II Type B1 Biosafety Cabinet

• Type A2 and Type B2 cabinetry are combined in these fittings. The inflow and the front part of the downflow are sucked into the front airflow grill, just like in Type A2, and then directed to a location under the work surface, from whence they can flow back towards the back of the cabinet. To reach the plenum, the air must travel vertically.
• Air is channelled downhill through the HEPA filter and into the workspace via this plenum, which is connected to the supply HEPA filter below it.
• This air flow is around 30% of the total airflow in the cabinet and is driven by the internal blower motor. Parallel to the primary air flow, an external exhaust blower drives a secondary air duct system.
• This second plenum is located at the back of the working area, and it is fed by an external blower that draws the downdraft from the back of the cabinet into an additional airflow grill. That external exhaust blow now draws 70% of its air from this plenum, which is connected to the exhaust HEPA filter.

Features

• The front opening.
• Sash.
• Exhaust HEPA filter.
• Supply plenum.
• Supply HEPA filter.
• Blower.
• Negative pressure exhaust plenum.

D. Class II Type B2 Biosafety Cabinet

• The Downward Velocity 100 fpm.
• No Re-circulation 100% air Exhausted Through HEPA Filter
• It Can be used for Radio Nucleotides and Toxic Chemicals 
• It is designed for Biosafety Levels 2 & 3User
• Provides Product, & Environment Protection 
• The Exhaust HEPA Filtered.
• Exhaust Hard Ducted out.

Working Principle of Class II Type B2 Biosafety Cabinet

• The internal motor in the Type B2 cabinet forces air through the supply HEPA filter and down into the working area.
• There is a vent at the top of the cabinet that brings fresh air into the room. In normal operation, the external exhaust blower draws air from the work area, where it has been mixed with air sucked in from the front access aperture.
• The internal motor’s sole responsibility is to draw air through the vent. Independent operation of the Type B2 cabinet is not possible.
• An external exhaust blower with sufficient force is required to draw air into the front of the cabinet and to continuously draw exhaust air out of the cabinet, via the ductwork, and back into the cabinet.
• If the exterior exhaust blower ever malfunctions and can no longer provide enough “pull” to keep air flowing that way toward the user, the internal blower must cease forcing air down into the work zone.
• The user could be exposed to harmful particles that have escaped the work area. HEPA filters are used to remove all of the air from the room.
• Because no air is recycled in these cabinets, they are ideal for tasks that require the release of chemical vapours.

Class II Type B2 Biosafety Cabinet Features

• The front opening
• Sash
• Exhaust HEPA filter
• Supply plenum
• Supply HEPA filter
• Blower
• The negative pressure exhaust plenum
• Container Supply Blower
• Filter screen

E. Class II Type C1 Biosafety Cabinet

• To our knowledge, this is the first biological safety cabinet to maintain an average inflow velocity of 105 feet per minute or higher via the sash aperture.
• You can use them as type A cabinets when recirculating, and as type B cabinets when exhausting.
• Rapid mode switching is possible in C1 cabinets by connecting or disconnecting the exhaust and recertifying the cabinet.
• A section of the lab is set aside for direct exhaust work with radionuclides or hazardous gases, and there is a distinct workspace separated from the storage and filing sections.

Working Principle of Class II Type C1 Biosafety Cabinet

Not connected to building exhaust

The front aperture of a Class II, Type C1 biosafety cabinet is situated under the sash, allowing ambient air to flow in. After being filtered, the air in the BSC’s workspace is routed to either a supply blower and supply filter or an exhaust blower and exhaust HEPA filter. HEPA filtration is used in the direct exhaust into the room.

Connected to building exhaust

The Class II, Type C1 biosafety cabinet is ventilated by an opening in the front, just below the sash. The air in the BSC’s workspace is then routed to either a supply blower and supply filter or an exhaust blower and exhaust HEPA filter. HEPA-filtered air is then released directly into the space. A canopy opening/gap at the building’s upper front allows outside air to enter the exhaust pipe directly, bypassing the BSC. Flexi-ducting provides an alternative route from the facility’s exhaust system to the exhaust duct.

3. Class III Biosafety Cabinet

• A Class III Biosafety Cabinet, also known as a “microbiological safety cabinet” or “total containment cabinet,” is a type of laboratory equipment designed to provide maximum protection for the user, the product, and the environment from highly infectious or dangerous biological agents, or agents with high potential of aerosolization.
• Class III cabinets are equipped with a number of advanced features to ensure complete containment of the agent. They have a sealed work area that is connected to an exhaust system that captures and filters all air exhausted from the cabinet. The cabinet also includes a supply of HEPA-filtered air that is fed into the cabinet to ensure that the work area remains at a slight positive pressure relative to the surrounding room, which help to prevent any leakage of the agent outside the cabinet.
• The operator works inside the cabinet through sealed gloves, which are attached to the front access opening of the cabinet. The operator must wear personal protective equipment (PPE) and the samples or reagents are manipulated through the gloves.
• The Class III Biosafety Cabinets are suitable for handling biological agents assigned to Risk Group 4 (RG4) such as Ebola virus, Lassa virus and agents with high potential for aerosolization like Bacillus anthracis (Anthrax) or airborne transmissible fungal organisms. They are also used for handling some toxins and dangerous chemicals or radioactive materials when the laboratory procedure requires it.
• In summary, Class III Biosafety Cabinets are designed to provide the highest level of protection for the user, the product, and the environment, particularly when working with highly infectious or dangerous biological agents or agents with high potential of aerosolization. They are typically found in high-security laboratories and are used by trained and certified personnel.

Working Principle of Class III Biosafety Cabinet

This sort of cabinet is pressure-tested to guarantee that no particles will leak out and enter the area. Two HEPA filters are employed to vent the filtered exhaust air outside. These metal-welded, gas-tight enclosures are outfitted with a front cabinet that has openings for the operator to utilise heavy-duty rubber gloves. Multiple glove boxes can be joined together to increase the size of the work area. A special exhaust system external to the cabinet maintains a negative pressure inside the cabinet. All items going into or out of the Class III cabinet can be sterilised in an attached autoclave with double doors. Class III BSCs need a pass-through box or dip tank with a HEPA-filtered exhaust system in order to be used for sterilisation.

The working mechanism of Class III Biosafety Cabinet typically involves the following steps:

1. Air Supply: A supply of HEPA-filtered air is fed into the cabinet to ensure that the work area remains at a slight positive pressure relative to the surrounding room. This helps to prevent any leakage of the agent outside the cabinet.
2. Containment: The cabinet is sealed and has a filtered exhaust system that captures and filters all air exhausted from the cabinet. This helps to prevent any contamination of the surrounding area and also helps to protect the operator and other laboratory staff from exposure to the agent.
3. Glove Port Access: The operator works inside the cabinet through sealed gloves, which are attached to the front access opening of the cabinet. The operator must wear personal protective equipment (PPE) and the samples or reagents are manipulated through the gloves.
4. Air Flow: Class III Biosafety Cabinets are designed to create a unidirectional airflow pattern that moves from the front of the cabinet to the back, which helps to prevent cross-contamination. The air flows into the cabinet through the front grille, over the work area, and is then exhausted out of the cabinet through the back grille.
5. HEPA Filter: The cabinet is equipped with a HEPA filter that captures and removes any particles that are present in the airflow. This includes any biological particles that may be present in the air as a result of the work being performed inside the cabinet.

In summary, Class III Biosafety Cabinets are designed to provide the highest level of protection for the user, the product, and the environment. They are used to handle highly infectious or dangerous biological agents or agents with high potential for aerosolization and rely on air pressure, filtered exhaust system and unidirectional airflow, HEPA filtration and glove-port access for maximum containment of hazardous agents.

Class III Biosafety Cabinet Features

• Include a rubber O-ring on the cabinet’s glove ports so that long gloves can be fastened to the storage unit.
• Sash.
• With two HEPA filters at the exhaust, the air quality is greatly improved.
• HEPA filters should be provided.
• Autoclave with two openings or a transparent box.
• Putting someone in a tank full of chemicals and seeing what happens.

Uses of Class III Biosafety Cabinet

Some common uses of Class III Biosafety Cabinets include:

• Handling and manipulation of highly infectious agents such as those in Risk Group 4 (RG4) – examples of these agents include Ebola, Marburg, Lassa fever and agents with high potential for aerosolization such as Bacillus anthracis (Anthrax) or airborne transmissible fungal organisms.
• Handling and manipulation of dangerous toxins and deadly viruses like smallpox.
• Handling and manipulation of radioactive materials or dangerous chemicals when the laboratory procedure requires it.
• Large-scale production of biological agents for research or medical purposes.
• Handling and manipulation of live or dead organisms that pose a serious danger to public health.
• Handling of biological materials that have been genetically modified and may have increased virulence or pathogenicity.

It’s important to note that a Class III Biosafety Cabinet provides the highest level of protection for user, samples, and surrounding environment, but it does not protect the operator from being contaminated from what’s inside the cabinet and must wear appropriate PPE and follow proper protocols for decontamination.

Advantages of Class III Biosafety Cabinets

• They provide the highest level of protection for the user, the samples, and the environment from highly infectious or dangerous biological agents or agents with high potential for aerosolization.
• They are sealed and have a filtered exhaust system that captures and filters all air exhausted from the cabinet, preventing any contamination of the surrounding area.
• They are equipped with HEPA filters that capture and remove any particles that are present in the airflow, including any biological particles.
• They are designed to create a unidirectional airflow pattern that helps to prevent cross-contamination.
• They have a glove port access which allows the operator to manipulate the samples and reagents without risking direct contact with the agents.

Disadvantages of Class III Biosafety Cabinets

• They are relatively expensive to purchase and maintain.
• They require trained and certified personnel to operate them safely.
• They are not suitable for handling all types of materials, such as toxic chemicals or radioactive materials.
• They are not suitable for all laboratory procedures, and only certain types of work can be performed inside them.
• They are large and take up significant laboratory space.
• They can be hot and uncomfortable to work in for long periods of time.

In summary, Class III Biosafety Cabinets are designed to provide the highest level of protection from highly infectious or dangerous biological agents or agents with high potential for aerosolization. They are typically used in high-security laboratories and are used by trained and certified personnel. While they have many advantages in terms of safety, they also have some disadvantages such as cost and space, and not being suitable for certain types of laboratory procedures.

Features of Class I, II, and III BSCs

Type	Face velocity (m/s)	Airflow (recirculated)	Airflow (exhausted)	Exhaust System
Class I	0.36	0	100	Hard duct
Class IIA1	0.38-0.51	70	30	Exhaust to room or thimble connection
Class IIA2	0.51	70	30	Exhaust to room or thimble connection
Class IIB1	0.51	30	70	Hard duct
Class IIB2 (Total Exhaust BSC)	0.51	0	100	Hard duct
Class III	NA	0	100	Hard duct

Ultraviolet Lamp

The Centers for Disease Control and Prevention (CDC) and the National Institutes of Health (NIH) concur that UV lights are not recommended nor necessary in biological safety cabinets (BSCs). UV lamps are unnecessary when BSCs are properly utilised and cleaned. If UV radiation is used as a secondary cleaning procedure, the following rules must be followed:

• When a room is occupied, UV lamps must be turned off to protect eyes and skin from UV radiation, which can burn the cornea and cause skin cancer. If the BSC has a sliding sash, it must be closed when the UV light is in operation.
• Numerous factors influence the activity of UV light’s germicidal impact.
• If UV lamps are placed, they must be cleaned weekly to remove any dust or grime that could diminish their germicidal efficacy.
• Lamps should be tested weekly with a UV metre to ensure that they emit UV light at the proper intensity: After five minutes of the lamp being on, the UV meter’s sensor is put in the centre of the work surface. The radiation output at a wavelength of 254 nanometers should not be less than 40 microwatts per square centimetre (nm).

Biological Safety Cabinets Operating Procedures (Steps of Using Biological Safety Cabinets)

The following safety instructions outline the proper usage of BSCs in the laboratory. Utilizing BSCs correctly protects the user and other laboratory employees against potential exposure to biohazardous chemicals.

1. Preparing BSC for Work

• Prior to beginning work, confirm that the BSC is currently certified (within the past 12 months) and running properly.
• If in use, turn off the germicidal UV light and examine the UV output log every week.
• Ensure that the sash is in the proper working position.
• Before beginning work, cabinet blowers must operate for 5 to 15 minutes to allow the BSC to purge particles. Consult the manufacturer’s instructions for the recommended purge time.
• Before beginning work, just prepare items essential for a certain activity and eliminate extraneous materials from the BSC.
• Adjust the height of the chair or stool so that the armpits are level with the base of the view screen or sash.

2. Personal Protective Equipment

• Lab coat buttons are required. If laboratory gowns with a back closure are worn for increased protection, they must be knotted. Lab coats with cuffs are recommended for ease donning. Not inside the sleeve, but over the wrists of lab coats, gloves should be worn.
• Refer to your laboratory’s IBC registration to see if additional PPE standards are required.

3. Pre-disinfection

• Spray or wipe the necessary disinfectant onto all interior surfaces.
• Allow air-dry

4. Assembly of materials and equipment

• Include only the supplies required to complete the procedure.
• Prepare the materials so that they do not come into contact with any contaminated materials.
• Place the hazardous materials container in the right rear position.
• Ensure that the view screen is properly positioned and secured.

5. Pre-purge cabinet

• When there is no activity indoors, allow the air to vent.

6. Working in the BSC

• Only supplies and equipment required for the current task should be stored in the BSC.
• Slowly move arms into and out of the cabinet perpendicular to the face opening to prevent disturbance of protective air flow patterns.
• After placing hands or arms within the cabinet, material manipulation should be delayed for one minute to allow the air to settle and “air sweep” the arms.
• Perform all tasks at least 4 inches from the front grille and on the work surface.
• Do not rest arms on the front grille unless the BSC is equipped with specific characteristics that allow this. This permits room air to flow directly into the workspace, rather than through the front grille. Instead, work with both arms slightly lifted.

7. Placement of Materials in the BSC

• Consider utilising horizontal discard trays containing an appropriate chemical disinfectant, aspiration devices, and collection jars for tips/serological pipettes to reduce the frequency of in-and-out arm movements.
• All items should be stored as far back as possible in the cabinet, toward the rear edge of the work area and away from the cabinet’s front grille.
• The cabinet should be arranged in such a way as to restrict the passage of soiled objects over clean ones. Ensure that active work flows over the work surface from the clean to the polluted area.
• Do not utilise or store equipment or supplies within the BSC that could disturb the BSC’s protective airflow pattern. If bulky equipment must be stored inside the BSC, position it as far back as possible. Behind the air split should be positioned the equipment.
• Do not obstruct the front grille with documents or other objects. If absorbent materials are utilised to aid in the cleanup and containment of spills, they should not be placed on the front grille.

8. Post-purge cabinet

• When there is no activity indoors, allow the air to vent.

9. Finish personally

• Remove your protective apparel and mask, and wash your hands.

10. Liquid Waste

• A vacuum flask system is necessary if a vacuum is used to protect the central building vacuum system and people who service the equipment.
• Connect the primary flask to a collection flask for overflow, followed by an in-line HEPA filter. Both flasks must contain a suitable disinfectant (such as bleach) for the item being utilised. Traps should be emptied routinely after waste has had sufficient contact time with the correct concentration of disinfection (e.g., 10% final concentration of bleach prior to disposal for at least 1 hour contact time due to high organic load).
• Using a secondary container, the vacuum flasks may be placed on the floor beneath or next to the BSC. If HEPA-filtered traps are located at eye level in the BSC, an overflow flask may be omitted.

11. Cleaning Spills in BSC

• To prevent pitting of steel surfaces, clean spills immediately using 10% bleach or another EPA-registered disinfectant for the required contact duration (e.g. 10 minutes), followed by 70% ethanol.
• Do not permit any potential contamination on the interior surfaces to stay, since this will raise the chance of infectious materials spreading beyond the BSC’s confinement.
• If liquid enters the vehicle through the front or rear grilles, stop the drain valves and pour 10% bleach or another EPA-approved disinfectant into the affected area. Allow sufficient contact time, for instance 10 minutes, and then drain. Follow with a 70% ethanol wash in the drain pans.
• When cleaning the BSC, handle paper towels and absorbent materials with care, since they may be sucked into the exhaust plenum. If this occurs, a certified BSC technician may need to open the cabinet to remove the object. This will also necessitate recertification of the BSC for use.

10. Post-disinfection

• Decontaminate surfaces and BSC contents using 10% bleach or another EPA-registered disinfectant for the proper contact duration (e.g. 10 minutes), followed by 70% ethanol to prevent pitting of steel surfaces. Allow no potential contaminants to stay on interior surfaces.
• At the end of each workday, surface disinfect any items to be removed from the BSC prior to their removal.
• The interior walls and window surfaces of the BSC should be decontaminated using 10% bleach or another EPA-registered disinfectant for the required contact period (e.g. 10 minutes), followed by 70% ethanol.
• Establish a regular (e.g., monthly) schedule for “deep” cleaning the BSC, which includes decontaminating all inside surfaces and under the grill surface to eliminate any contamination.
• When work is complete, the cabinet should run for three to five minutes without interruption to purge the work area of airborne contaminants.

11. Shut down cabinet

• Turn off the fan and fluorescent lighting before turning on the UV bulb.

Start up and Shut Down procedures

Start up procedures

• If the room is equipped with a UV steriliser, turn it off as soon as you enter.
• Turn on all ventilation fans and cabinet lighting.
• Allow 5 minutes for the system to be purged; inspect the flow alarm system and the visual alarm function (if so equipped).
• Decontaminate interior surfaces that are readily accessible using a disinfectant suited to the agents or suspected agents present.

Start Down procedures

• Decontaminate and remove all interior work area items.
• Decontaminate interior surfaces that are readily accessible using a disinfectant suited to the agents or suspected agents present.
• Turn on ultraviolet steriliser (if so equipped). Caution: Never rely solely on UV irradiation to disinfect a polluted work space.
• Allow 5 minutes for the system to be purged.
• Turn off the fan’s motor.

Applications of Biological Safety Cabinets

Biological safety cabinets (BSCs) are used in a wide range of laboratory settings to provide a physically and biologically contained workspace for activities involving potentially harmful biological materials. Some common applications of BSCs include:

1. Microbiology: BSCs are commonly used in microbiology laboratories to conduct experiments and tests on microorganisms such as bacteria, viruses, and fungi. They provide a protected space for handling, culturing, and observing these microorganisms. Most common uses are;
   • Unlocking containers with pressures other than atmospheric
   • Animal inoculation by the nasal route
   • Collecting infectious tissues/fluids or fertilised eggs
   • Mortuary examination of diseased animals
   • Transfer procedures
   • Specimen separation
   • Sonication
   • Blending and Grinding
   • Aliquoting
   • Vortex-mixing \sCentrifugation
   • Utilization of pipettes and other laboratory procedures
2. Cell Culture: BSCs are used in cell culture laboratories to protect the laboratory worker and environment from exposure to potentially harmful cell lines. They provide a controlled environment for maintaining and manipulating cells, including culturing, staining, and observing.
3. Molecular Biology: BSCs are used in molecular biology laboratories to conduct experiments and tests on DNA, RNA and proteins. They provide a protected space for handling and manipulating samples, including PCR, DNA sequencing, and protein purification.
4. Biotechnology: BSCs are used in biotechnology laboratories to protect laboratory workers from exposure to genetically modified organisms (GMOs) and other biologically-derived products. They provide a controlled environment for genetic engineering, fermentation and downstream processing.
5. Pathology: BSCs are used in pathology laboratories to protect laboratory workers from exposure to potentially hazardous material, and to maintain the integrity of the samples during manipulation and processing.
6. Industrial Laboratories: BSCs are used in Industrial Laboratories to protect laboratory workers from exposure to biological hazards while handling of samples, testing, and production of biosensors, bioprocessing, and biotechnology products.

Advantages of Biological Safety Cabinets

Biological safety cabinets (BSCs) are a critical piece of equipment in many laboratory settings, providing a protected space for working with potentially harmful biological materials. Some key advantages of BSCs include:

1. Protection of the laboratory worker and environment: BSCs provide a physical and biological barrier that helps protect the laboratory worker and the environment from exposure to potentially harmful biological materials.
2. Improved containment: BSCs are designed to physically contain biological materials and prevent them from escaping into the laboratory environment, providing an additional layer of protection.
3. Better air flow management: BSCs have an internal ventilation system that constantly circulates filtered air, ensuring that the air inside the cabinet is free of contaminants.
4. Enhanced Safety: BSCs are designed with a number of safety features, such as safety interlock switch, to ensure that the cabinet is used correctly and safely.
5. Improved work surface: BSCs have a work surface that is impervious to liquids and easy to decontaminate, providing a protected space for working with biological materials.
6. Increased Efficiency: BSCs allow for a more controlled and efficient manipulation of samples and reagents, increasing the quality of results and reducing the chance of contamination.
7. Cost-effective: BSCs are cost-effective in the long run as they reduce the need for frequent decontamination and replacement of reagents, samples and equipment.
8. Compliance: BSCs are crucial for compliance with laboratory safety regulations and help to prevent occupational exposure to harmful biological agents.
9. Flexibility: BSCs come in different sizes and designs, making them suitable for a wide range of laboratory settings and applications.
10. Contamination of the sample: It safeguards against sample contamination.

Overall, BSCs are a valuable addition to any laboratory that works with biological materials and are a key tool for maintaining a safe and productive working environment.

Limitations of Biological Safety Cabinets

Biological safety cabinets (BSCs) are a critical piece of equipment in many laboratory settings, providing a protected space for working with potentially harmful biological materials. However, there are also some limitations to consider when using BSCs:

1. Limited access: BSCs have a limited working space and access to the samples and equipment inside may be hindered. This can lead to increased difficulty in handling and manipulating samples, especially larger ones.
2. Reduced mobility: BSCs are stationary equipment and cannot be easily moved from one location to another, which can limit their use in certain areas of the laboratory.
3. Noise: BSCs have an internal ventilation system that can be noisy, which can be disruptive to the laboratory environment.
4. Maintenance: BSCs require regular maintenance and calibration to ensure they are functioning properly and safely. This includes regular cleaning and replacement of filters, which can be time-consuming and costly.
5. Cost: BSCs can be expensive to purchase, install and maintain.
6. Limited visbility: Due to the design and functionality of BSCs, it may be difficult to observe the experiments and samples inside, especially for large-scale or long-term experiments.
7. Limited amount of materials: BSCs have a limited amount of space, so the number of samples and reagents that can be used inside the cabinet at one time is also limited.
8. Limited Accessory compatibility: not all laboratory equipment and accessory can be used inside the BSC, so it may limit the type of experiments that can be performed.

Precautions

Biological safety cabinets (BSCs) are an important piece of laboratory equipment that provide a protected space for working with potentially harmful biological materials. To ensure safe and effective use of a BSC, it is important to follow established safety precautions:

1. Proper Training: all workers should be properly trained on the safe operation, maintenance and decontamination procedures for the BSCs. They should also be aware of emergency procedures in case of malfunction.
2. PPE: Laboratory workers should wear appropriate personal protective equipment (PPE) when working with a BSC, including gloves, a lab coat, and a face mask or shield.
3. Pre-use Inspection: Before using a BSC, it should be inspected to ensure that it is clean, functioning properly, and in compliance with applicable regulations.
4. Airflow: The airflow in the BSC should be checked and maintained as per manufacturer’s instruction to ensure the cabinet is functioning properly.
5. Cleaning: BSCs should be cleaned and decontaminated regularly to prevent the build-up of biological contaminants. Cleaning should be done with appropriate disinfectants and according to the manufacturer’s instructions.
6. Safety Interlock: Some BSCs have a safety interlock switch, which prevents the cabinet from being operated if the sash window is not closed properly. Always make sure that the sash window is closed before turning on the BSC.
7. Biosafety level: Always match the biosafety level of the cabinet with the work you are doing.
8. Limited use: Do not use the BSC for tasks that are not appropriate for the class of cabinet, or that can generate excessive aerosols or splashes.
9. Access: only authorized personnel should have access to the BSC, and everyone should be aware of the dangers of working with biological materials and the proper procedures to follow in case of an accident or exposure.
10. Emergency: have an emergency plan and procedure in case of power failure or malfunction.

By following these precautions, you can ensure the safe and effective use of your BSC and protect yourself and your colleagues from exposure to harmful biological materials.

Examples of Biological Safety Cabinets

There are different types and models of BSCs available, each designed to provide a different level of protection. Here are some examples of BSCs:

1. Class I BSC: The LabGard ES NU-428 is a Class I BSC that is designed for work with low-risk biological materials such as bacteria and fungi. It features an exhaust ventilation system that filters the air flowing into and out of the cabinet, and a work surface that is impervious to liquids and easy to decontaminate.
2. Class II BSC: The MicroSafe BSC is a Class II BSC that is intended for work with moderate-risk biological materials, such as viruses and human cell lines. It features a recirculating air system that filters the air inside the cabinet, and a work surface that is impervious to liquids and easy to decontaminate.
3. Class III BSC: The FlexGard BSC is a Class III BSC that is intended for work with high-risk biological materials, such as pathogenic microorganisms and prions. It provides a completely sealed and separate environment for the handling of extremely hazardous materials and equipped with additional safety features such as a double-door entry system and special glove ports for access to the work area.

These are just a few examples of BSCs available in the market, and different manufacturers offer different types, designs, and sizes of BSCs. it is important to match the biosafety level of the cabinet with the work you are doing, consult the manufacturer or lab safety expert to ensure compliance with all applicable regulations.

Differences Between Class I, Class II, Class III Biosafety Cabinet

Class I, Class II, and Class III Biosafety Cabinets are types of ventilated laboratory workspaces that provide different levels of protection for the worker, the materials being handled, and the environment.

Class I Biosafety Cabinet:

• It is also called a “open front” cabinet or “horizontal laminar flow” cabinet.
• It provides personnel protection by keeping the operator away from the sample, but it does not protect the sample or the environment.
• It works by drawing in air through a HEPA filter, which removes particles before it is exhausted back into the laboratory.
• Its mainly used for work with low risk microorganisms, such as most laboratory-acquired infections, and low-level hazardous chemicals, as well as for plant growth studies.

Class II Biosafety Cabinet:

• it is also called a “closed front” cabinet.
• It provides both personnel and environmental protection, as well as sample protection, but not as much as a Class III.
• It works by drawing in air through a HEPA filter, which removes particles, and then recirculating the filtered air back into the work area through a laminar flow process.
• It is mainly used for work with microorganisms of moderate risk, such as some laboratory-acquired infections and agents that are contagious through respiratory droplets.

Class III Biosafety Cabinet:

• It is also called a “total containment” cabinet.
• It provides the highest level of personnel, environmental and sample protection.
• It works by drawing in air through a HEPA filter, which removes particles, and then recirculating the filtered air back into the work area through a laminar flow process.
• The exhaust air is also passed through HEPA filter before exhausting out.
• It is mainly used for work with microorganisms of highest risk, such as dangerous and exotic pathogens, as well as for work with highly toxic chemicals and radioactive materials.

It’s important to note that the exact requirements for a biosafety cabinet can vary depending on the specific application, and the classification may change based on national and international biosafety regulations.

What is the principle of biosafety cabinet?

The principle of a Biosafety Cabinet (BSC) is to provide a barrier between the work being done and the environment, and also to filter and remove potentially contaminated air before it is exhausted. This protects both the worker and the surrounding environment from potential exposure to infectious agents or other hazardous materials.

There are two main types of Biosafety Cabinets, Laminar Flow BSC, and Cellular BSC.

1. Laminar Flow BSC: They use a HEPA filtered laminar airflow that is directed downward or across the work surface to protect the samples, the workers and the environment. The air is either exhausted out of the cabinet or recirculated back into the work area after passing through HEPA filter.
2. Cellular BSC: It uses individual, isolated compartments to protect the samples, the workers, and the environment.

In both types, the BSCs create a controlled environment with a defined airflow pattern which minimize the risk of contamination and exposure.

What are the 4 biosafety levels?

There are four levels of biosafety (BSL-1 to BSL-4) established by the Centers for Disease Control and Prevention (CDC) in the United States, and similar organizations internationally, that describe the risk of microorganisms and the appropriate laboratory practices and techniques required to handle them safely.

1. Biosafety Level 1 (BSL-1): agents are considered to have a low potential for causing disease in healthy individuals and are typically found in the environment. The laboratory practice and techniques required for BSL-1 are similar to those for a normal laboratory.
2. Biosafety Level 2 (BSL-2): agents are considered to be of moderate risk and may cause infection through broken skin or mucous membranes. The laboratory practice and techniques required for BSL-2 are more stringent than for BSL-1 and include the use of personal protective equipment (PPE) and a biosafety cabinet.
3. Biosafety Level 3 (BSL-3): agents are considered to be of high risk and may cause severe or lethal infections. The laboratory practice and techniques required for BSL-3 include the use of PPE and specialized laboratory facilities, such as a BSL-3 laboratory or a BSL-3 laboratory animal facility.
4. Biosafety Level 4 (BSL-4): agents are considered to be extremely hazardous and may cause life-threatening infections with no known treatments. The laboratory practice and techniques required for BSL-4 include the use of PPE, specialized laboratory facilities, and procedures that are specifically designed to prevent the release of the agent. BSL-4 laboratories are typically highly restricted and are only found in a few locations worldwide.

These biosafety levels provide guidance for the safe handling, use, and disposal of microorganisms and other potentially hazardous materials, and also help to minimize the risk of laboratory-acquired infections and the accidental release of pathogens into the environment.

Biosafety Cabinet Working Animated Video

FAQ

References

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