Biosafety Cabinet Principles: How They Work and How to Use Them Effectively

A biosafety cabinet is a primary engineering control that protects laboratory personnel, the product being handled, and the surrounding environment from exposure to infectious aerosols and particulate hazards. It works by combining high-efficiency particulate air filtration with directed airflow patterns that create a physical and aerodynamic barrier between the operator and the work zone. For laboratory students, technicians, researchers, and diagnostic professionals, understanding these principles is the foundation for safe and effective cabinet use. This article explains how HEPA filtration and airflow design achieve containment, how to operate a cabinet correctly, how to recognize and respond to performance problems, and what records and checks support reliable operation.

At a Glance: Biosafety Cabinet Functions and Key Operational Checks

The table below summarizes the main protective functions of a biosafety cabinet, the design feature that provides each function, and the operational check that verifies it is working.

What a Biosafety Cabinet Does and What It Does Not Do

A biosafety cabinet is an enclosed, ventilated workspace that uses HEPA filtration to remove particles from air moving through the cabinet. HEPA filters are designed to capture particles at a specified efficiency, and the cabinet directs filtered air in patterns that contain aerosols generated during work. The cabinet provides three types of protection depending on its class and design: protection for the operator, protection for the sample or product, and protection for the room environment.

A biosafety cabinet is not a chemical fume hood. Chemical fume hoods exhaust air to the outside and are designed to remove chemical vapors and fumes. Biosafety cabinets recirculate air through HEPA filters, which do not capture gases or vapors. Using volatile chemicals or radioisotopes in a biosafety cabinet can create a hazard because the vapors are not removed by the filter and may be recirculated into the work zone or exhausted into the room. The Laboratory Biosafety Manual from the World Health Organization provides guidance on matching the cabinet type to the work being performed.

A biosafety cabinet also does not eliminate the need for good microbiological technique. The cabinet contains aerosols that are generated, but the operator's movements, the placement of materials, and the handling of infectious agents determine whether aerosols are created in the first place. Proper training in aseptic technique is essential for safe cabinet use, as noted in a review of the role of biosafety cabinets in preventing infection in the clinical laboratory 11.

HEPA Filtration: The Core of Cabinet Performance

HEPA filtration is the mechanism by which biosafety cabinets remove particles from air. A HEPA filter is a pleated sheet of fine fibers that captures particles through several physical processes, including interception, impaction, and diffusion. The filter medium is designed to achieve a high collection efficiency for particles in the most penetrating particle size range, which is typically around 0.3 micrometers in diameter.

The filter does not act like a sieve that blocks particles larger than a certain size. Instead, it captures particles across a range of sizes through the combined effects of the fiber matrix. Particles that contact a fiber are held by adhesion forces. The filter efficiency is tested and certified according to standards, and a filter that passes certification is considered capable of removing particles at the rated efficiency.

In a biosafety cabinet, HEPA filters are placed in specific locations depending on the cabinet class. A Class II cabinet, which is the most common type in clinical and research laboratories, uses a supply HEPA filter that provides clean air to the work zone and an exhaust HEPA filter that cleans air before it is released. The Laboratory Quality Management System Handbook from the World Health Organization describes the role of the cabinet in the broader quality system of a laboratory, including the need for regular certification of cabinet performance.

The integrity of the HEPA filter is critical to cabinet performance. A filter that is damaged, improperly installed, or past its service life can allow particles to pass through, compromising both product protection and personnel protection. Filter integrity is verified during cabinet certification using a method that challenges the filter with an aerosol and measures penetration. A study of 360 Class II biosafety cabinets in Beijing found that HEPA filter integrity was one of the performance indicators assessed during certification testing 7. The study reported an overall qualified rate of 70.4 percent across all tested cabinets, meaning that a substantial proportion of cabinets in the field had at least one performance indicator that did not meet the standard.

Airflow Patterns in Class II Biosafety Cabinets

The protective function of a Class II biosafety cabinet depends on two airflow systems: the inflow and the downflow. These two air streams work together to create a barrier at the front opening and to provide clean air over the work surface.

The inflow is the air that enters the cabinet through the front opening. This air moves inward, toward the work zone, and is drawn into the front grille. The inward flow prevents aerosols generated inside the cabinet from escaping into the room. If the inflow velocity drops below the required level, the barrier is weakened and aerosols may escape.

The downflow is the HEPA-filtered air that moves downward from the top of the cabinet onto the work surface. This air is split at the front grille, with a portion being drawn into the front grille and the remainder being drawn into the rear grille. The downflow provides a curtain of clean air over the work zone, protecting the samples from contamination.

The balance between inflow and downflow is critical. The cabinet is designed so that the downflow air that reaches the front grille is drawn into the grille, preventing the inward airflow from being pushed back out of the opening. If the downflow is too high, it can overcome the inflow and cause air to spill out of the front opening. If the downflow is too low, the work zone may not receive adequate clean air.

The performance evaluation study of Class II cabinets found that inflow velocity, downflow velocity, and illumination had relatively lower qualified rates compared to other indicators 7. This finding highlights the importance of regular airflow testing, because airflow problems may not be visible to the operator during routine use.

Cabinet Classes and Their Applications

Biosafety cabinets are classified according to their design and the level of protection they provide. The main classes are Class I, Class II, and Class III.

A Class I cabinet provides personnel and environmental protection but does not provide product protection. Air is drawn into the cabinet through the front opening and is exhausted through a HEPA filter. Class I cabinets are used for work with agents that require containment but where product sterility is not a concern.

A Class II cabinet provides personnel, product, and environmental protection. It is the most widely used cabinet in clinical and research laboratories. Class II cabinets are further divided into types based on their exhaust systems and the amount of air they recirculate. Some types exhaust air back into the room through a HEPA filter, while others exhaust to the outside through a dedicated duct.

A Class III cabinet is a fully enclosed, gas-tight cabinet with glove ports. All air is filtered through HEPA filters, and the cabinet operates under negative pressure. Class III cabinets are used for work with highly hazardous agents that require the highest level of containment.

The Laboratory Biosafety Manual provides guidance on selecting the appropriate cabinet class based on the risk group of the agent and the nature of the work. The manual emphasizes that the cabinet is one component of a complete biosafety program that includes facility design, personal protective equipment, and standard operating procedures.

How the Cabinet Protects the Operator, the Sample, and the Environment

The three types of protection provided by a biosafety cabinet are often described as personnel protection, product protection, and environmental protection. Each type of protection is achieved through a specific combination of airflow and filtration.

Personnel protection is achieved by the inward airflow at the front opening. This airflow captures aerosols that are generated during procedures such as pipetting, mixing, or opening containers. The aerosols are drawn into the front grille and are captured by the HEPA filters. A review of biosafety cabinets in clinical laboratories noted that the cabinet controls the distribution of infectious substances and stops the spread of disease 11.

Product protection is achieved by the downflow of HEPA-filtered air over the work surface. This air sweeps across the work zone and prevents airborne contaminants from settling on the samples. The downflow also helps to remove particles that are generated during work, carrying them to the grilles for capture.

Environmental protection is achieved by the exhaust HEPA filter. Air that leaves the cabinet passes through this filter, which removes particles before the air is released into the room or the outside environment. This protects people who are not working at the cabinet from exposure to infectious aerosols.

The effectiveness of these protections depends on the cabinet being used correctly. A study of biosafety precautions in diagnostic laboratories in Khartoum state, Sudan, found that only 5.8 percent of the 190 laboratories surveyed had a biosafety cabinet 6. The study also found low compliance with other biosafety measures, including written standard operating procedures and spill cleanup procedures. This finding illustrates that the presence of a cabinet is not sufficient for safety, the cabinet must be part of a broader system of training, procedures, and oversight.

Preparing the Cabinet for Use

Proper preparation of the biosafety cabinet before work begins is essential for maintaining the protective airflow and preventing contamination. The preparation process includes visual inspection, surface decontamination, and allowing the cabinet to run for a period to purge the work zone.

Before starting work, the operator should visually inspect the cabinet for any signs of damage or obstruction. The front grille and rear grille should be clear of debris, paper, or other materials that could block airflow. The work surface should be clean and free of spills from previous work. The airflow alarm and any other indicators should be checked to confirm that the cabinet is operating normally.

The work surface and the interior walls of the cabinet should be decontaminated with an appropriate disinfectant before work begins. The disinfectant should be compatible with the cabinet materials and effective against the agents being handled. The operator should allow the disinfectant to remain in contact with the surfaces for the recommended contact time before wiping it dry.

After decontamination, the cabinet should be allowed to run for several minutes before work begins. This purges the work zone of any airborne particles that may have settled during the idle period. The Laboratory Quality Management System Handbook emphasizes that the cabinet is part of the laboratory's quality system and that procedures for cabinet use should be documented and followed consistently.

Loading the Cabinet and Arranging Materials

The arrangement of materials inside the cabinet has a direct effect on the airflow and on the protection provided. Materials should be placed so that they do not block the grilles or disrupt the airflow patterns.

All work should be performed at least several inches inside the front edge of the work surface. This keeps the work within the zone where the airflow is stable and provides the best protection. Materials should be placed on the work surface in a way that leaves the front grille and rear grille unobstructed.

Large equipment, such as a centrifuge or a tube rack, should be placed toward the rear of the work surface. This minimizes the disruption to the airflow at the front of the cabinet. Items that are not needed for the immediate work should be removed from the cabinet to reduce clutter and to avoid creating surfaces where aerosols can settle.

The operator should minimize the number of movements in and out of the cabinet during work. Each time the arms are removed from the cabinet and reinserted, the airflow is disturbed and the risk of contamination increases. Materials should be gathered and organized before work begins so that the operator does not need to reach in and out repeatedly.

The review of biosafety cabinets in clinical laboratories noted that laboratory employees are instructed in aseptic procedures, proper hand posture, and efficient personal protection when working in the cabinet 11. These instructions are designed to reduce the chance of contaminating the surrounding area and to ensure that the cabinet is used effectively.

Working Inside the Cabinet: Technique and Movement

The technique used by the operator while working inside the cabinet is as important as the cabinet design. Poor technique can generate aerosols, disrupt airflow, and compromise the protection provided by the cabinet.

The operator should move slowly and deliberately when working inside the cabinet. Rapid movements can create turbulence that disrupts the airflow and allows aerosols to escape. The arms should be moved in and out of the cabinet slowly, and the hands should be held in a position that does not block the airflow.

Work should be performed on a solid surface, such as a tray or a mat, instead of directly on the work surface. This makes cleanup easier and reduces the risk of spills spreading. Any spill that occurs inside the cabinet should be cleaned up immediately, following the laboratory's spill response procedures.

The operator should avoid talking, coughing, or sneezing while working inside the cabinet. These actions can generate aerosols that may contaminate the work zone. If the operator needs to speak or step away from the cabinet, the work should be paused and the hands should be removed from the cabinet.

Pipetting and other liquid-handling procedures should be performed carefully to minimize aerosol generation. The operator should avoid creating bubbles, splashes, or sprays. Pipette tips should be ejected into a waste container inside the cabinet, and the waste container should be closed before it is removed from the cabinet.

Decontamination and Shutdown Procedures

When work is complete, the cabinet must be decontaminated before it is shut down or before the next user begins work. The decontamination process removes any infectious material that may have settled on the work surface or the interior walls.

The work surface, the interior walls, and any equipment that was used inside the cabinet should be wiped with an appropriate disinfectant. The disinfectant should be applied to all surfaces and allowed to remain in contact for the recommended contact time. After the contact time has elapsed, the surfaces should be wiped dry with a clean cloth.

Any waste generated during the work should be removed from the cabinet and disposed of according to the laboratory's waste management procedures. Waste containers should be closed and sealed before they are removed from the cabinet. The Laboratory Biosafety Manual provides guidance on the management of laboratory waste, including the treatment of infectious waste before disposal.

After decontamination, the cabinet should be allowed to run for several minutes to purge the work zone of any residual aerosols. The cabinet can then be shut down according to the manufacturer's instructions. Some cabinets are equipped with ultraviolet lights that can be used for additional decontamination, but the ultraviolet light is not a substitute for surface decontamination with a disinfectant. The ultraviolet light only affects surfaces that are directly exposed, and it does not penetrate dust or debris.

A study of a biosafety cabinet equipped with an ozone generator evaluated the effectiveness of ozone treatment during transition periods between the production of cell products 13. The study found that ozone exposure significantly reduced colony-forming units and endotoxin levels in Pseudomonas aeruginosa, and it also reduced the colony formation of Bacillus subtilis endospores and Aspergillus brasiliensis spores. This finding suggests that ozone treatment may be useful for decontaminating cabinets between processes, but it does not replace the need for routine surface decontamination with a disinfectant.

Routine Performance Checks and Certification

Biosafety cabinets require regular performance testing to verify that they are operating correctly. This testing is typically performed by a qualified certifier who uses specialized equipment to measure airflow, filter integrity, and other performance indicators.

The certification process includes tests for inflow velocity, downflow velocity, HEPA filter integrity, airflow smoke patterns, and other indicators. The results of these tests are compared to the standards that apply to the cabinet. A cabinet that meets all the standards is considered qualified for use.

The performance evaluation study of 360 Class II biosafety cabinets in Beijing provides a real-world picture of cabinet performance 7. The study used 1,803 performance testing records from 2018 to 2023 and found that the overall qualified rate was 70.4 percent. The median service life of the cabinets was 7 years, with an interquartile range of 5 to 10 years. The study found no significant difference in the qualified rate between domestic and imported cabinets, but it did find that inflow velocity, downflow velocity, and illumination had relatively lower qualified rates compared to other indicators.

These findings have practical implications for laboratory managers. A cabinet that is past its expected service life may be more likely to have performance problems. A cabinet that fails certification should be taken out of service until the problem is corrected. The certification records should be reviewed regularly to identify trends in cabinet performance.

The Laboratory Quality Management System Handbook describes the role of the biosafety cabinet in the laboratory's quality system. The handbook emphasizes that the cabinet is a critical piece of equipment that must be maintained and tested to ensure that it continues to provide the required level of protection.

Common Failure Patterns and Troubleshooting

Biosafety cabinets can develop problems that affect their performance. Recognizing the signs of a problem and responding appropriately is essential for maintaining safety.

Airflow Alarms

Most biosafety cabinets are equipped with an airflow alarm that sounds when the airflow drops below the required level. The alarm may be triggered by a blocked grille, a failed blower, a dirty filter, or a problem with the exhaust system. When the alarm sounds, the operator should stop work immediately and close any open containers. The operator should then check the obvious causes, such as a blocked grille or an open exhaust damper. If the cause is not apparent, the laboratory should contact the certifier or the manufacturer for assistance.

Contamination of the Work Zone

Contamination of the work zone can occur even when the cabinet is operating correctly. The most common cause is poor technique, such as moving the arms in and out of the cabinet too quickly, blocking the airflow with equipment, or failing to decontaminate the work surface before use. If contamination is detected, the operator should review their technique and consider whether the cabinet is being used correctly.

HEPA Filter Leaks

A leak in the HEPA filter can allow particles to pass through the filter, compromising the protection provided by the cabinet. Filter leaks can be caused by damage to the filter medium, improper installation, or aging of the filter. Filter integrity is tested during certification, and a cabinet with a leaking filter should be taken out of service until the filter is replaced.

Unusual Noise or Vibration

Unusual noise or vibration from the cabinet may indicate a problem with the blower or the motor. The cabinet should be inspected by a qualified technician, and the cabinet should not be used until the problem is corrected.

Visible Airflow Disturbance

A smoke test can be used to visualize the airflow patterns in the cabinet. If the smoke test shows that the airflow is not moving in the expected pattern, the cabinet may have a problem with the blower, the filters, or the grilles. The cabinet should be taken out of service and inspected.

The study of biosafety risk identification in BSL-3 laboratory facilities used a fault analysis event tree method to identify and analyze risk points 9. The study found that risk assessments can help rank the seriousness of identified risks and reduce the overall biosafety risk level of the facility. This approach can be applied to biosafety cabinet management by identifying the most likely failure modes and implementing controls to prevent them.

Records and Documentation

Accurate records are essential for managing biosafety cabinets and for demonstrating compliance with laboratory standards. The records should include the following information:

• Cabinet identification, including the manufacturer, model, and serial number
• Date of installation and date of each certification
• Results of each certification test, including airflow velocities and filter integrity
• Dates of filter replacements and any repairs
• Records of any alarms or malfunctions and the actions taken
• Training records for operators

The Laboratory Quality Management System Handbook emphasizes the importance of documentation in the laboratory quality system. The handbook describes the requirements for equipment records, including the need to document maintenance, calibration, and certification activities.

The certification records should be reviewed regularly to identify trends in cabinet performance. For example, if the inflow velocity has been declining over several certification cycles, the cabinet may need a new filter or a blower adjustment. Early identification of these trends can prevent a cabinet failure that could compromise safety.

Training and Competency

Operator training is a critical component of biosafety cabinet safety. A cabinet that is used incorrectly can fail to provide the required protection, even if it is operating correctly. Training should cover the principles of cabinet operation, the correct techniques for working inside the cabinet, and the procedures for responding to problems.

The review of biosafety cabinets in clinical laboratories noted that proper training of the BSC is essential for preventing infections 11. The review emphasized that laboratory employees are instructed in aseptic procedures, proper hand posture, and efficient personal protection when working in the cabinet.

Training should be provided to all new operators before they are allowed to work in the cabinet. Refresher training should be provided on a regular basis, and retraining should be provided when there are changes in procedures or equipment. The training records should be maintained as part of the laboratory's quality system.

The study of biosafety precautions in Khartoum state diagnostic laboratories found that laboratory personnel awareness towards biosafety principles implementation was very low 6. The study found that only 16.8 percent of laboratories had appointed biosafety officers, and only 23.7 percent had written standard operating procedures. These findings highlight the need for ongoing training and oversight to ensure that biosafety principles are implemented consistently.

Limitations of Biosafety Cabinets

Biosafety cabinets have limitations that must be understood by all users. The cabinet is not a substitute for other biosafety measures, and it cannot protect against all hazards.

The cabinet does not protect against chemical hazards. HEPA filters do not capture gases or vapors, so volatile chemicals should not be used in a biosafety cabinet unless the cabinet is specifically designed for that purpose. The Laboratory Biosafety Manual provides guidance on the use of chemicals in biosafety cabinets.

The cabinet does not protect against all routes of exposure. The cabinet contains aerosols, but it does not protect against exposure through direct contact with contaminated surfaces or through needlestick injuries. Personal protective equipment, such as gloves and laboratory coats, is still required when working in the cabinet.

The cabinet can be affected by the environment in which it is installed. Air currents from doors, windows, ventilation systems, and foot traffic can disrupt the airflow at the front opening. The cabinet should be located away from these sources of air disturbance, and the area around the cabinet should be kept clear.

The cabinet requires regular maintenance and certification to continue providing the required level of protection. A cabinet that is not maintained can fail without warning, exposing the operator and the environment to infectious aerosols.

Professional Escalation Criteria

Laboratory personnel should know when to escalate a problem with a biosafety cabinet to a supervisor, a biosafety officer, or a qualified certifier. The following situations require escalation:

• The airflow alarm sounds and the cause cannot be identified and corrected immediately
• The cabinet fails certification testing
• A HEPA filter leak is detected
• The cabinet produces unusual noise or vibration
• There is visible damage to the cabinet, the filters, or the grilles
• A spill of infectious material occurs inside the cabinet and cannot be contained
• An operator experiences a potential exposure to infectious material while working in the cabinet

The Laboratory Quality Management System Handbook describes the requirements for incident reporting and investigation in the laboratory quality system. Any incident involving a potential exposure should be reported and investigated to identify the cause and to prevent recurrence.

The study of biosafety risk identification in BSL-3 laboratory facilities found that risk assessments can help identify the most serious risks and prioritize actions to reduce them 9. This approach can be applied to biosafety cabinet management by conducting a risk assessment for each cabinet and using the results to guide maintenance, training, and oversight activities.

Biosafety Cabinet Use in Diagnostic Laboratories

Diagnostic laboratories handle infectious agents and potentially infectious materials from patients and animals. The biosafety cabinet is a critical tool for protecting laboratory workers and preventing the spread of disease in these settings.

A review of the role of biosafety cabinets in preventing infection in the clinical laboratory noted that clinical laboratories are essential in healthcare to better diagnose, treat, and track medical diseases 11. However, handling infectious organisms in these laboratories puts the safety of laboratory workers and the general public at risk. The review highlighted that biosafety cabinets have become crucial tools in guaranteeing laboratory safety by controlling the distribution of infectious substances and stopping the spread of diseases.

The study of biosafety precautions in Khartoum state diagnostic laboratories found that the standards of biosafety precautions adopted by the diagnostic laboratories in the study area were very low 6. The study found that only 5.8 percent of the 190 laboratories surveyed had a biosafety cabinet, and only 23.7 percent had written standard operating procedures. The study concluded that laboratory personnel awareness towards biosafety principles implementation was very low.

These findings have implications for diagnostic laboratories in all settings. The presence of a biosafety cabinet is not sufficient for safety. The cabinet must be used correctly, maintained regularly, and supported by a broader system of training, procedures, and oversight.

Biosafety Considerations for Zoonotic Agents

Laboratories that handle zoonotic agents, such as nontuberculous mycobacteria or mpox virus, must consider the transmission pathways and the biosafety protocols that apply to these agents.

Nontuberculous mycobacteria are an ecologically diverse group of environmental mycobacteria that are increasingly recognized as an important cause of human and animal disease 8. While most infections arise from environmental exposure, evidence from outbreak reports and genomic epidemiology suggests animal-associated and device-associated transmission pathways that intersect with human occupational and clinical risk. The review of zoonotic nontuberculous mycobacteria presented a tiered diagnostic framework, ranging from microscopy and culture to targeted polymerase chain reaction, whole-genome sequencing, and emerging metagenomic and artificial intelligence-based pipelines 8. The review also discussed biosafety considerations and reporting standards for laboratories that handle these agents.

Mpox is a zoonotic disease that may infect both humans and animals 10. It usually spreads by direct contact with bodily fluids, lesion material, or fomites, and by prolonged face-to-face contact. Mpox can spread to laboratory animals in a research laboratory through either a general outbreak or during procedures. The review of mpox transmission risks and biosafety protocols in laboratory animal research discussed the need to understand the transmission risk and biosafety protocol to be in place in laboratory settings to prevent an outbreak and probably contain an outbreak 10.

Laboratories that handle zoonotic agents should conduct a risk assessment to determine the appropriate biosafety level and the required containment measures. The biosafety cabinet is a key component of the containment strategy, but it must be used in conjunction with other measures, including personal protective equipment, standard operating procedures, and waste management protocols.

Frequently Asked Questions

What is the difference between a biosafety cabinet and a chemical fume hood?

A biosafety cabinet uses HEPA filters to remove particles from the air and provides protection for the operator, the sample, and the environment. A chemical fume hood exhausts air to the outside and is designed to remove chemical vapors and fumes. HEPA filters do not capture gases or vapors, so volatile chemicals should not be used in a biosafety cabinet unless the cabinet is specifically designed for that purpose. The Laboratory Biosafety Manual provides guidance on selecting the appropriate containment equipment for the work being performed.

How often should a biosafety cabinet be certified?

Biosafety cabinets should be certified at least annually, and they should also be certified after any maintenance or repair that could affect their performance. The certification process includes tests for inflow velocity, downflow velocity, HEPA filter integrity, and other performance indicators. A study of 360 Class II biosafety cabinets in Beijing found that the overall qualified rate was 70.4 percent, indicating that a substantial proportion of cabinets in the field had at least one performance indicator that did not meet the standard 7. Regular certification is essential for identifying and correcting performance problems.

What should I do if the airflow alarm sounds while I am working in the cabinet?

Stop work immediately and close any open containers. Check the obvious causes, such as a blocked front grille or rear grille, an open exhaust damper, or a door or window that is creating an air current. If the cause is not apparent, remove your hands from the cabinet and contact the laboratory supervisor or the certifier. Do not resume work in the cabinet until the problem has been identified and corrected.

Can I use a biosafety cabinet to work with volatile chemicals?

No. HEPA filters do not capture gases or vapors, so volatile chemicals can accumulate in the work zone or be released into the room. The Laboratory Biosafety Manual provides guidance on the use of chemicals in biosafety cabinets. If you need to work with volatile chemicals, use a chemical fume hood or a biosafety cabinet that is specifically designed for that purpose.

How long should I run the cabinet before starting work?

The cabinet should be allowed to run for several minutes before work begins to purge the work zone of any airborne particles that may have settled during the idle period. The exact time may vary depending on the cabinet model and the laboratory's standard operating procedures. The Laboratory Quality Management System Handbook emphasizes that procedures for cabinet use should be documented and followed consistently.

What is the difference between a Class II, Type A and a Class II, Type B biosafety cabinet?

Class II biosafety cabinets are divided into types based on their exhaust systems and the amount of air they recirculate. Type A cabinets recirculate a portion of the air through HEPA filters and exhaust the remainder back into the room through a HEPA filter. Type B cabinets exhaust air to the outside through a dedicated duct. The Laboratory Biosafety Manual provides guidance on selecting the appropriate cabinet type based on the nature of the work and the agents being handled.

How do I know if my biosafety cabinet is protecting me properly?

The cabinet provides protection when it is operating correctly and when it is used correctly. The certification records confirm that the cabinet meets the performance standards. The operator's technique determines whether the protection is effective. The operator should follow the laboratory's standard operating procedures for cabinet use, including proper preparation, loading, and decontamination. The review of biosafety cabinets in clinical laboratories noted that proper training is essential for preventing infections 11.

What should I do if I spill infectious material inside the cabinet?

Clean up the spill immediately, following the laboratory's spill response procedures. Apply an appropriate disinfectant to the spill and allow it to remain in contact for the recommended contact time. Wipe up the disinfectant and the spill material with a clean cloth, and dispose of the waste according to the laboratory's waste management procedures. Decontaminate the work surface and any equipment that was contaminated. Report the spill to the laboratory supervisor, and document the incident according to the laboratory's procedures.

Related Diagnostic Guides

• Understanding Ct Values in qPCR: What They Mean and How to Use Them
• Common Gram Staining Errors and How to Fix Them
• How to Decontaminate a Biosafety Cabinet: UV Light, Chemical, and HEPA Filter Considerations
• Negative Controls in Western Blotting: Why They Matter and How to Use Them
• Common Contamination Sources in Microbiology Labs and How to Prevent Them

References and Further Reading

• Laboratory Quality Management System Handbook. World Health Organization.
• Laboratory Biosafety Manual. World Health Organization.
• Assay Guidance Manual. National Center for Advancing Translational Sciences.
• Bioanalytical Method Validation Guidance. U.S. Food and Drug Administration.
• NCBI Literature Resources. National Center for Biotechnology Information.
• Assessment of biosafety precautions in Khartoum state diagnostic laboratories, Sudan.. The Pan African medical journal, 2012.
• Performance evaluation of biological safety cabinets: a real-world analysis.. 2026.
• Zoonotic Nontuberculous Mycobacteria: Transmission Pathways, Laboratory Diagnosis, Detection Methodologies, and One Health Priorities.. 2026.
• The study of biosafety risk identification and analysis for facilities in biosafety level 3 laboratories.. 2025.
• MPOX transmission risks and biosafety protocols in laboratory animal research.. 2026.
• The Role of the Biosafety Cabinet in Preventing Infection in the Clinical Laboratory.. 2023.
• Selection,Installation and Operation of Biosafety Cabinet. 2010.
• Changeover method for biosafety cabinets using ozone gas. PLoS ONE, 2025.
• Biosafety cabinet capable of prompting life of ultraviolet lamp. 2013.
• Easily-cleaned biosafety cabinet. 2012.
• Biosafety cabinet with time control system. 2011.
• EVALUATION OF THE PROTECTION PERFORMANCE OF A BIOSAFETY CABINET AFTER REPLACING THE FILTER. 2008.
• Development of Hyperpurificatory Biosafety Cabinet. 2008.
• Primary Engineering Controls in Pharmaceutical Compounding, Part 2: Biosafety Cabinets.. International journal of pharmaceutical compounding, 2020.

This article is educational and does not replace validated laboratory procedures, institutional biosafety review, manufacturer instructions, or professional interpretation.