Biosafety Cabinets – Its Definition and Classes ( I,II, III)


Biosafety cabinets are essential in laboratories because they protect both researchers and the environment. These specialized control systems are intended to offer a safe environment for handling hazardous items such as infectious agents and poisonous substances. Understanding biosafety cabinets’ purpose, components, and appropriate application is critical for ensuring a safe and secure laboratory environment.

Purpose of Biosafety Cabinets

Biosafety cabinets are designed to keep possible biohazards away from laboratory staff, research materials, and the surrounding environment. They form a physical barrier that keeps dangerous chemicals from entering the laboratory and reduces the chance of contamination. 

Functions of biosafety Cabinets

The basic roles of biosafety cabinets are as follows:

  • Containment: Biosafety cabinets create a controlled environment in which hazardous materials are kept inside and prevented from escaping into the laboratory.
  • Protection: They protect laboratory staff by limiting their exposure to biohazards through the use of efficient airflow systems and HEPA filters.
Image source: Pro-Lab Diagnostics.

Types of Biosafety Cabinets 

There are several varieties of biosafety cabinets available, each with a varied level of protection and application suitability. Among the most common are:

Cabinets for Class I Biosafety

Class I cabinets protect both Laboratory personel and the environment, but they do not safeguard research materials from contamination. These cabinets feature a front entrance and pull air into a negative pressure zone through a HEPA filter.

Applications and Features

Class I cabinets are often utilized in applications involving low to moderate-risk substances, such as identification of  non pathogenic microbial procedures and research activities requiring a Biosafety Level 2 (BSL-2) containment level.

Cabinets for Class II Biosafety

Class II cabinets provide both personnel and environmental protection, as well as research material protection. They are further categorized as Type A1, Type A2, Type B1, and Type B2.

Types of biosafety cabinet class II

Type A1 cabinets recycle a part of the air through a HEPA filter before exhausting the remainder into the laboratory or through a separate exhaust system.

Type A2 cabinets: Like Type A1, these cabinets recycle some air but exhaust a greater percentage to the environment after passing through a HEPA filter.

Type B1 cabinets have an entrance of air through a HEPA filter and an exhaust of air to the laboratory or a specialized exhaust system.

Type B2 cabinets: These cabinets include a specialized exhaust system that entirely eliminates air from the cabinet, adding an extra layer of safety.

Features, Distinctions, and Applications

Class II biosafety cabinets are often used in laboratories that operate with BSL-2 and BSL-3 agents, providing a sterile working environment for activities such as cell culture, microbiology, and infectious materials research.

Cabinets for Class III Biosafety

Class III cabinets are the most secure and store the most information. These cabinets are entirely enclosed, with glove ports for manipulating the contents. The researchers operate while wearing airtight gloves that are fixed to the cabinet.

Applications and Features

Class III cabinets are used in maximum containment facilities to handle very hazardous substances or microorganisms such as BSL-4 diseases. They provide total isolation and protection, allowing researchers to deal with dangerous viruses and bacteria in a safe environment.

Factors to Consider When Choosing a Biosafety Cabinet

Several considerations should be addressed when purchasing a biosafety cabinet for a laboratory to guarantee it fits the particular standards. These elements are as follows:

Requirements for Biosafety Levels

The amount of containment necessary for the laboratory should influence the selection of a suitable biosafety cabinet, as determined by the type of agents being handled.

Airflow and containment characteristics

It is critical to understand the airflow patterns within the cabinet as well as the amount of confinement offered. Unidirectional airflow cabinets with strong containment characteristics improve safety.

Cabinet Dimensions and Configuration

The biosafety cabinet’s size and layout should be appropriate for the laboratory area and the type of work being done. The number of people working at the same time, as well as the size of the equipment needed, should be considered.

Energy Conservation and Certification

Choosing an energy-efficient biosafety cabinet lowers operational expenses while also contributing to environmental sustainability. Furthermore, choosing a cabinet that has been verified by regulatory agencies guarantees that it meets safety criteria.

Components of a Biosafety Cabinet


A biosafety cabinet’s workzone is the area where researchers handle the items. To guarantee user comfort and productivity, the workzone must be designed with ergonomic considerations.

Ergonomic Design for User Comfort

The workzone should be designed to reduce physical strain on researchers and allow them to work comfortably for long periods of time. Adjustable work tables, footrests, and armrests that promote appropriate posture are examples of ergonomic features.

Airflow Patterns 

Different filters (discuss below), are used in biosafety cabinets to catch and remove airborne particles, including pathogens. It is critical to understand the airflow patterns within the cabinet in order to use it properly.

Airflow Control System

A biosafety cabinet’s airflow system is in charge of producing and maintaining a regulated atmosphere within the workzone.

Air Supply and Exhaust

Biosafety cabinets take air, filter it to eliminate pathogens, and then circulate it within the cabinet. The filtered air is subsequently expelled, either directly into the laboratory or via a separate exhaust system.

Concept of Directional Airflow

The directional airflow design guarantees that air flows throughout the cabinet from clean to polluted parts at all times. This reduces the risk of dangerous chemicals or microbes escaping and protects both the researcher and the environment.

Negative Pressure and Control

To prevent the escape of airborne pollutants, biosafety cabinets are intended to maintain a negative pressure environment. This negative pressure guarantees that any leaks in the cabinet attract air into the cabinet rather than releasing it.

HEPA filters

HEPA filters, which remove particles as fine as 0.3 microns with a 99.97% efficiency, are essential components of biosafety cabinets.

Function and Purpose

HEPA filters act as a barrier, preventing harmful particles from being released from the cabinet into the surrounding environment. They are critical in safeguarding researchers and keeping the work environment clean. for best performance, HEPA filters must be maintained on a regular basis and replaced on time. Filter integrity testing and following suggested replacement schedules are required to ensure the filters’ effectiveness.

Alarms and the Control Panel

The control panel of a biosafety cabinet allows researchers to monitor and alter numerous parameters in order to preserve safety within the work zone. Researchers may use the control panel to adjust the airflow velocity, illumination, and other cabinet operations. It might have a display that shows characteristics like airflow, temperature, and filter status.

Monitoring and alarms are quite important.

Monitoring systems and alerts notify researchers of any deviations from the specified parameters, such as a decrease in airflow velocity or a faulty filter. Prompt notice allows for corrective steps to be made to keep the workplace safe.

Visibility and lighting

The biosafety cabinet’s illumination and visibility are critical for precise and safe operations. Biosafety cabinets should have adequate illumination to guarantee vision within the work zone. Adequate illumination minimizes the likelihood of mistakes and improves manipulation precision.

UV lights

Ultraviolet light should be in the safety cabinet for decontaminating the cabinet before and after use. It is more important know that it should be off while working in the cabinet as exposure to it is more harmful to laboratory personnel

Work instructions for biosafety cabinet

PPE (Personal Protective Equipment)

Personal protection equipment (PPE) is required for researchers working in biosafety cabinets to ensure their safety.

Gowning and Dressing Procedures

Before entering the biosafety cabinet, researchers should follow established protocols for donning PPE such as gowns, gloves, masks, and goggles. This stops the individual from coming into close touch with the harmful elements.

Gloves, masks, and Goggles: Selection and Application

Appropriate selection and usage of personal protective equipment (PPE) such as gloves, masks, and goggles provide an extra layer of protection against biohazards. It is critical to choose PPE that is compatible with the agents being handled and to dispose of contaminated PPE appropriately after usage.

Aseptic Procedures

Aseptic methods are critical for keeping the biosafety cabinet sterile and preventing cross-contamination.

Material Handling in a Sanitary Environment

Aseptic practices should be used to guarantee that things handled within the cabinet stay sterile. Handwashing, surface disinfection, and the use of sterile devices and containers are all part of this.

Avoid Cross-Contamination 

To prevent cross-contamination between samples, equipment, and work surfaces, strict precautions should be taken. This involves adequate cleaning and disinfection practices, item segregation, and avoiding needless cabinet movements.

Decontamination Procedures 

The biosafety cabinet must be decontaminated on a regular basis to ensure a clean and safe working environment.

Disinfection and cleaning

Cleaning and disinfection procedures should be created and performed to eliminate any potential sources of contamination. This involves applying the proper disinfectants and adhering to the prescribed contact times. In most cases, we use 70 % ethanol to decontaminate the biosafety cabinet.

Maintenance and Certification

Biosafety cabinets must be maintained and tested on a regular basis to ensure their continuous effectiveness and safety.

Testing for Filter Integrity

Regular filter integrity testing ensures that the HEPA filters are operating correctly and at the desired efficiency level. This testing should be carried out in accordance with a specified schedule or as directed by the manufacturer.

Airflow Velocity Calculation

The airflow velocity within the cabinet is measured and verified to ensure that the proper airflow patterns are maintained. This may be done using specialist devices and should be done on a frequent basis.

Alarm and sensor calibration

The biosafety cabinet’s alarms and sensors should be calibrated on a regular basis to guarantee its accuracy and dependability. This calibration guarantees that researchers are notified as soon as any deviations from the parameters are detected.

Certification of Biosafety Cabinets

Biosafety cabinets must be certified by competent specialists to guarantee compliance with safety standards and regulatory requirements.

The Value of Certification

Certification ensures that the biosafety cabinet satisfies the appropriate performance, safety, and containment criteria. It guarantees that the cabinet works properly and offers the necessary amount of protection.

Process of Testing and Certification

The testing and certification procedure includes a comprehensive examination of the cabinet’s performance, including airflow patterns, filter integrity, and containment. These examinations are conducted by certified specialists, who provide the relevant documents upon completion.

Recertification Frequency

Recertification should be done on a regular basis to verify the biosafety cabinet’s continued efficacy and safety. Recertification frequency may vary depending on factors such as regulatory requirements, kind of work performed, and cabinet usage.

Procedures for Emergencies

Being prepared for crises and having well-defined protocols in place are critical for assuring researcher safety and reducing risks.

Backup Systems and Power Failure

Backup power solutions, such as uninterruptible power supply (UPS), aid in maintaining ventilation and containment during power outages, limiting the unintentional escape of hazardous chemicals.

Spill and Accident Response

Establishing processes for the fast and safe handling of spills and mishaps, including adequate containment, cleaning, and reporting, reduces the effect of occurrences and assures researcher safety.


Biosafety cabinets are essential laboratory equipment because they provide a regulated and safe environment for handling biohazards. Understanding the function, components, and best practices of biosafety cabinets is critical for ensuring a safe working environment. Researchers may efficiently use biosafety cabinets to safeguard themselves, the materials, and the surrounding environment by following the right protocols, applying safety measures, and refuting common fallacies.

Difference between biosafety cabinet and fume hood

Biosafety cabinets and fume hoods, contrary to common opinion, perform distinct functions. While fume hoods primarily protect researchers from chemical fumes, biosafety cabinets offer a controlled environment for dealing with biohazards while also safeguarding both researchers and the environment.

Does Biosafety Cabinets give 100 % Personal Protection

Biosafety cabinets provide substantial protection, although they are not intended to give total personal protection. To reduce hazards, researchers must still use suitable PPE and adhere to safe work procedures.

Does All Biosafety cabinets have their specific use?

Yes, Biosafety cabinets are classified and constructed for certain uses and levels of confinement. It is critical to choose the right cabinet based on the agents being handled and the amount of confinement necessary.

Does the biosafety cabinet require any certifications?

Biosafety cabinets must be certified and recertified on a regular basis to ensure their performance and safety. Annual certification or adherence to the approved timetable ensures that safety requirements are met on an ongoing basis.


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Ujala Shabbir
Ujala Shabbir

Ujala Shabbir is a microbiologist pursuing her MPhil in Microbiology at the University of Veterinary and Animal Sciences in Lahore. Her research is focused on the "preparation of calcium-conjugated FMDV vaccine and its comparative immunogenicity with other vaccine delivery systems".
She completed her Bachelor of Science degree in Applied Microbiology from the same university in 2021 with a CGPA of 3.72/4.
During her undergraduate studies, she took various microbiology-related courses and gained practical experience through internships.

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