Laminar Flow Hood

The laminar flow hood is one of the most important pieces of equipment in a cell culture lab. Laminar air flow hoods come in many varieties with distinct levels of protection based on air filtration, exhaust, and direction of air flow. Cell culture labs typically use biosafety cabinets, a type of laminar flow hood, for cell and tissue culture. They provide an aseptic work area while allowing the containment of infectious splashes or aerosols generated by many microbiological procedures. Three categories of biosafety cabinets, designated as Class I, II, and III, have been developed to help meet varying research and clinical needs at the proper Biosafety Levels (BSL). The class level determines the level of protection that the hood provides for cell cultures, the surrounding environment, and lab personnel.

Laminar flow hoods are used to protect a sensitive work area from dust and other airborne contaminants. Laminar air flow refers to the constant, unidirectional flow of HEPA-filtered air over the work area to protect the product from potential contaminants. This helps to minimize disturbances in the air and enables that particles behave in a predictable manner. Using a HEPA filter in the hood further enhances its aseptic nature by capturing and removing airborne contaminants from the air.

A cell culture hood and a biosafety cabinet are both types of laminar flow hoods. However, not all biological safety cabinets are appropriate to use as cell culture hoods. Class I biosafety cabinets do not protect cultures from contamination and should not be used in cell and tissue culture work. 

In a cell culture lab, a Class II or higher biosafety cabinet is generally referred to as a cell culture hood or a tissue-culture hood because the level of protection they provide to the culture, personnel, and environment is suitable for most cell culture laboratories. The goal of this level of protection in a cell culture hood is to prevent cell culture contamination, which can cause extensive issues. These hoods mitigate the chance of wasting valuable time and laboratory resources, helping making them an economical way to protect your culture experiments. 

For a more detailed guide to the appropriate cell culture hood for your lab, please refer to the latest edition of the Biosafety in Microbiological and Biomedical Laboratories (BMBL)  from the CDC and NIH.

Please note: horizontal laminar flow or vertical laminar flow “clean benches” are not biosafety cabinets; these pieces of equipment discharge HEPA-filtered air from the back of the cabinet across the work surface toward the user, and they may expose the user to potentially hazardous materials. These devices only provide product protection. Clean benches can be used for certain clean activities where sample protection is required, including in hospitals, pharmaceutical applications, cleanrooms, and various industrial applications, however, they should never be used when handling cell culture materials for mammalian cell culture. 

When looking for a cell culture hood, it’s imperative to identify the biosafety levels (BSL) of the materials you are working with and determine the class level of the hood that is required to handle materials safely. Class types are the best way to identify if a hood is safe for your laboratory’s BSL risk. However, some biosafety cabinets and laminar air flow hoods are still not appropriate for culturing cells, such as clean benches and Class I BSCs.

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. Most cell culture labs should be at least BSL-2, but the exact requirements depend upon the cell line used and the type of work conducted

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 cell culture hood should be large enough to be used by one person at a time, be easy to clean inside and outside, have adequate lighting, and be comfortable to use without requiring awkward positions. Keep the workspace in the cell culture hood clean and uncluttered and keep everything in your direct line of sight. Disinfect each item placed in the cell culture hood by spraying it with 70% ethanol and wiping clean.

The arrangement of items within the cell culture hood usually adheres to the following right-handed convention, which can be modified to include additional items used in specific applications.

• A wide, clear workspace in the center with your cell culture vessels
• Pipettor in the front right, where it can be reached easily
• Reagents and media in the rear right to allow easy pipetting
• Tube rack in the rear middle holding additional reagents
• Small container in the rear left to hold liquid waste

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.