Biosafety Cabinets Explained: Class I, II, and III for Modern Labs
A biosafety cabinet protects people, samples and the environment by filtering air in a controlled pattern. This guide explains Class I, Class II (Types A1, A2, B1 and B2) and Class III cabinets, how they differ from fume hoods, how standards and certification work, and what to check before buying a used biosafety cabinet.
Josh Bray
Oct 24, 2026
Quick Answer
A biosafety cabinet protects people, samples and the surrounding environment by pulling air through filters in a controlled pattern. Class I cabinets protect the user and the environment but not the sample, Class II cabinets protect all three, and Class III cabinets enclose the work completely for the highest-risk agents. Choose the class from your risk assessment, then check certification, filters and ducting before you buy new or used.
What Is a Biosafety Cabinet?
A biosafety cabinet is an enclosed, ventilated workspace that keeps hazardous biological material away from the people working with it. It moves air in precise patterns and passes that air through filters, so particles never reach the user or the room. Some designs also protect the sample from contamination.
You may see the same equipment called a biological safety cabinet or a microbiological safety cabinet. The names point to one family of equipment, and the class and type tell you what protection you get. That detail matters because choosing the wrong cabinet puts people at risk and can ruin your work.
Class I Biosafety Cabinets
A Class I cabinet draws unfiltered room air across the work surface and through the front opening, then exhausts it through a HEPA filter. The airflow works in a similar way to a chemical fume hood. It protects the user and the environment, but it offers no product protection, because room air flows over your sample.
Labs use Class I cabinets to enclose equipment such as centrifuges, harvesters and small fermenters, and for tasks that create aerosols, such as tissue homogenisation. Some models recirculate filtered air back into the room, and those filters may need more frequent replacement.
Class II Biosafety Cabinets
Class II is the workhorse of cell culture and microbiology, because it protects the user, the sample and the environment together. Air enters through the front grille, and HEPA-filtered air flows downward over the work in smooth, laminar lines. Disrupting that air curtain raises the risk of release and contamination, so good technique matters as much as good equipment.
Type A1 and Type A2
A1 and A2 cabinets may recirculate filtered air back into the laboratory, or they may exhaust through a canopy connection. Of the Class II types, only A2, B1 and B2 should handle volatile toxic chemicals, and only in limited amounts that respect exposure limits.
Type B1 and Type B2
B1 and B2 cabinets must exhaust outdoors through a fixed or canopy connection. A B2 cabinet exhausts everything it draws in, which makes it the usual choice when you work with larger amounts of volatile chemicals alongside biological agents. These cabinets need suitable ducting and a building that can support it, so plan the installation before you shop.
Class III Biosafety Cabinets
A Class III cabinet is a gas-tight enclosure with a non-opening view window. You work through long, heavy-duty rubber gloves, and materials move in and out through a dunk tank or a double-door pass-through box that can be decontaminated between uses. Both supply and exhaust air pass through HEPA filters, and the exhaust passes through two filters, or a filter and an air incinerator, before it leaves the building.
Labs choose Class III for highly infectious agents and hazardous operations where maximum protection for the worker and the environment is essential. The enclosure demands more effort and training than other classes, so you only specify it when your risk assessment calls for it.
Biosafety Cabinet vs Fume Hood
Many people confuse the two. A fume hood protects you from chemical vapours by drawing them away, while the cabinet filters air to remove particles. HEPA filters do not capture volatile chemicals or gases, so a standard cabinet does not replace a fume hood for solvent work. Match the equipment to the hazard you actually face.
Choosing the Right Class for Your Work
Start with your risk assessment, because it names the agents you handle, the procedures you run and the level of protection you need. If you only need to protect people while enclosing equipment, a Class I cabinet may be enough. If you also need a clean work area for cell culture or sterile preparation, step up to Class II. Pick Type A for general work, and Type B when you handle volatile chemicals alongside biological agents. Reserve Class III for the highest-risk agents, and ask your biosafety adviser to confirm the choice, since they know your local rules.
Using a Cabinet Correctly
Good equipment still depends on good technique. Keep clutter away from the front grille, because blocked grilles disturb the air curtain. Work deep inside the cabinet, move your arms slowly and avoid sweeping motions that pull room air in. Wipe down surfaces before and after each session with a disinfectant suited to your agent, and keep the sash at the height the manufacturer sets.
Plan the layout so clean items sit on one side and waste on the other, which reduces cross-contamination. Avoid open flames, which disturb the airflow, and train every new user before first use. Record that training, because auditors and inspectors will ask for it.
Comparing the Classes at a Glance
| Class | Airflow | Protects | Exhaust | Typical use |
|---|---|---|---|---|
| Class I | Room air drawn in, HEPA-filtered exhaust | User and environment | Filtered, may recirculate in some models | Enclosing centrifuges, fermenters and aerosol tasks |
| Class II, Type A1 and A2 | Inflow at the front, HEPA-filtered downflow | User, sample and environment | Recirculated to the lab or canopy exhaust | Cell culture and general microbiology |
| Class II, Type B1 and B2 | Inflow at the front, HEPA-filtered downflow | User, sample and environment | Ducted outdoors | Work involving volatile chemicals with biological agents |
| Class III | Gas-tight enclosure with glove ports | Environment and user, maximum level | Double HEPA or HEPA plus incinerator | Highly infectious agents |
Standards and Certification
Standards give each class a measurable performance target. In North America, NSF/ANSI 49 classifies cabinets into classes and types based on the performance and protection each must meet. In Europe and the UK, EN 12469 covers microbiological safety cabinets and sets similar criteria.
Certification keeps those targets honest. A qualified technician should test airflow and filter integrity on a regular schedule, after any repair and after any move. UK employers should check HSE guidance on biological agents and follow the testing schedule set by their own biosafety adviser. A cabinet must also be fully decontaminated before it moves and recertified once it is in place, which matters a great deal if you buy second-hand.
Buying a Used Biosafety Cabinet
A used unit can deliver the same protection as a new one when it has been looked after. Ask the seller for the latest certification report, and for a decontamination certificate if the cabinet has moved. Check the HEPA filter condition and installation date, the blower, the sash, the alarms and the airflow monitor, then review the service history.
Match the type to your site as well. Type B cabinets need ducting, so confirm your building can accept one. Measure ceiling height, door width and bench space before delivery, and budget for recertification after installation. A cabinet that fits your workflow and your building will serve your lab for years.
How Machinery Masters Can Help
Machinery Masters is a UK-based marketplace for new and used industrial and laboratory equipment, with verified sellers and financing available for qualified buyers. The Safety, Containment and Controlled Environments collection includes biosafety and containment cabinets alongside related lab safety equipment.
Tell us what you need through Start Buying and machine matches arrive in your inbox within minutes. If you want to spread the cost, see our financing options. Replacing a cabinet and need to sell the old one? Create an advert and generate your listing in minutes.
Frequently Asked Questions
What is the difference between Class I, II and III biosafety cabinets?
Class I protects the user and the environment but not the sample. Class II protects the user, the sample and the environment. Class III is a gas-tight glove enclosure that gives the highest level of containment.
Which cabinet class do most labs use for cell culture?
Most cell culture labs use Class II cabinets, because they keep the culture clean while protecting the operator. Your risk assessment decides the exact type.
Can a biosafety cabinet handle chemical fumes?
Not by default. HEPA filters do not capture volatile chemicals or gases, and only A2, B1 and B2 cabinets suit small amounts of volatile toxic chemicals. Use a fume hood for solvent work.
How often does a cabinet need certification?
Follow your site's testing schedule and your biosafety adviser. Cabinets also need certification after repairs and after any move, and a moved cabinet must be decontaminated first.
Is it safe to buy a used biosafety cabinet?
Yes, when you verify its certification, filter condition, decontamination history and service records. Plan for recertification once the cabinet is installed.