Laminar Flow Hoods vs Biosafety Cabinets for Cell Culture

Laminar flow hoods and biosafety cabinets are both commonly used in laboratories that require sterile working conditions. Although laminar flow hoods are often mentioned in discussions about cell culture, most modern biomedical laboratories perform mammalian cell culture work in a Class II biosafety cabinet. Laminar flow hoods (also known as clean benches) use HEPA-filtered, unidirectional airflow to protect samples from contamination. However, because they do not provide protection for laboratory personnel or the surrounding environment, they are not appropriate for mammalian cell culture applications.

Biosafety cabinets—sometimes informally referred to as “cell culture hoods”—are designed to provide a higher level of protection. In addition to HEPA-filtered laminar airflow that protects the culture, they incorporate inward airflow and filtered exhaust to help contain potentially infectious splashes or aerosols generated during microbiological procedures. Biosafety cabinets are categorized into three classes (Class I, II, and III), each intended to meet specific research and clinical needs based on risk assessment and Biosafety Level (BSL) considerations. The cabinet class determines the degree of protection provided for the culture, laboratory personnel, and the surrounding environment.

Laminar flow hoods are designed to protect a sensitive work area from dust and other airborne contaminants. Laminar airflow refers to the constant, unidirectional flow of HEPA-filtered air across the work surface, which helps maintain a sterile environment by reducing turbulence and promoting predictable particle movement. The HEPA filtration system captures and removes airborne contaminants, providing product protection for materials handled within the cabinet.

Horizontal and vertical laminar flow“clean benches” are not biosafety cabinets. These devices discharge HEPA-filtered air across the work surface and may direct airflow toward the user. As a result, they provide product protection only and do not offer personnel or environmental protection. Clean benches may be appropriate for certain non-hazardous applications requiring sterility, such as pharmaceutical compounding, electronics assembly, or other controlled industrial processes. However, they should never be used when handling mammalian cell culture materials or other potentially infectious biological samples.[1]

A biosafety cabinet (BSC), also known as a biological safety cabinet, is a ventilated workstation designed to safely handle infectious microorganisms and other hazardous biological materials. BSCs help maintain the sterility of cell cultures, reduce cross-contamination, and protect product integrity. Most cabinets use High-Efficiency Particulate Air (HEPA) filters in their supply and exhaust systems to remove harmful particles from the air.

Biosafety cabinets are classified as Class I, II, or III based on the level of protection they provide. Class I cabinets protect personnel and the environment but do not provide product protection. Class II cabinets provide personnel, product, and environmental protection and are widely used for mammalian cell culture applications. Class III cabinets are fully enclosed systems designed for high-containment work.

A properly certified and well-maintained BSC is the primary means of containment in many laboratories and serves as a key engineering control within a broader biosafety program of appropriate laboratory practices and procedures. When selecting a BSC, laboratories must evaluate the hazards of any chemicals used, including carcinogens and toxic substances, as part of their overall risk assessment and decision-making process.

The main difference between laminar flow hoods and biosafety cabinets is the level of protection they apply to the product (or culture), user, and environment. This level of protection is established by the direction and filtration of the airflow. Despite their similarity in appearance and use in similar settings, laminar flow hoods and biosafety cabinets serve distinctly different purposes.

Laminar flow hoods (also called clean benches) and biosafety cabinets are both laboratory enclosures that use HEPA-filtered airflow, but they are designed for different purposes. A laminar flow hood provides product protection only by directing unidirectional, HEPA-filtered air across the work surface. Because airflow may be directed toward the user, clean benches do not provide personnel or environmental protection and are not appropriate for mammalian cell culture work.

Biosafety cabinets (BSCs), by contrast, are containment devices designed to protect the laboratory personnel and the surrounding environment. Class II biosafety cabinets—commonly referred to informally as “cell culture hoods” or “tissue culture hoods”—protect the culture, in addition to personnel and the environment. They combine laminar HEPA-filtered airflow with inward airflow and filtered exhaust to contain potentially infectious or toxic aerosols. For this reason, Class II BSCs are standard equipment in most cell culture laboratories.[1]

Selection of the appropriate biosafety cabinet should be based on a formal risk assessment and institutional biosafety guidelines, such as those outlined in the CDC and NIH publication Biosafety in Microbiological and Biomedical Laboratories (BMBL).[1]

When choosing a biosafety cabinet, it’s important to consider the Biosafety Level (BSL) of the agents and materials being handled, along with the types of procedures performed in the laboratory. Biosafety levels are assigned through a formal risk assessment process and define the containment practices, safety equipment, and facility requirements necessary for safe work. Cabinet class selection should be determined by institutional biosafety guidance and the level of personnel, product, and environmental protection needed.

BSL-1 is the basic level of protection common to most research and clinical laboratories and is appropriate for agents that are not known to cause disease in normal, healthy humans.

BSL-2 is appropriate for moderate-risk agents known to cause human disease of varying severity by ingestion or through percutaneous or mucous membrane exposure. Many mammalian and human-derived cell culture systems are handled at BSL-2 due to potential adventitious or latent infectious agents.

BSL-3 is appropriate for indigenous or exotic agents with a known potential for aerosol transmission, and for agents that may cause serious and potentially lethal infections.

BSL-4 is appropriate for exotic agents that pose a high individual risk of life-threatening disease by infectious aerosols and for which no treatment is available. These agents are restricted to high containment laboratories.

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A biosafety cabinet (often informally referred to as a “cell culture hood”) should be appropriately sized for single-user operation, easy to clean inside and out, equipped with adequate lighting, and ergonomically designed to minimize awkward positioning. Keep the workspace clean and uncluttered, and maintain all materials within your direct line of sight to help preserve aseptic technique and proper airflow.

Before placing materials into the cabinet, disinfect the exterior surfaces using 70% ethanol or another appropriate laboratory disinfectant.

Proper arrangement of materials inside the biosafety cabinet helps maintain laminar airflow and reduce the risk of contamination. A common right-handed workflow arrangement includes:

• A wide, clear workspace in the center with your cell culture vessels
• Pipettor positioned at the front right for easy access
• Reagents and media placed toward the rear right to facilitate controlled pipetting
  
• Tube rack positioned in the rear center holding additional reagents
• Small container in the rear left designated for liquid waste

Figure 1. The basic layout of a biosafety cabinet (commonly referred to as a cell culture hood) for right-handed workers. Left-handed workers may switch the positions of the items laid out on the work surface.

1. US Department of Health and Human Services, Center for Disease Control and Prevention, National Institutes of Health (2020, June) Biosafety in Microbiological and Biomedical Laboratories 6th Edition. Apr 2024.