Beginners guide to buying and validating biosafety cabinets
Buying and validating a biosafety cabinet comes down to three things: choosing the right class for your biohazard risk, siting it correctly, and testing it regularly to prove it still protects people, product, and environment. A biosafety cabinet is the primary engineering control in any laboratory that handles hazardous biological materials, using HEPA filtration to contain the viruses, bacteria, bodily fluids, and aerosols that would otherwise put staff and work at risk. Get the specification and installation right, and it does that job reliably for years.
Choosing the right class
Start by identifying the risks, hazards, and substances the cabinet will handle, because that risk assessment determines the class you need. There are three classes, each offering a different level of protection.
- Class 1 biosafety cabinets protect the operator and the environment, but not the product. Air is drawn in away from the user and filtered before it is exhausted, which suits low to moderate risk work where the sample itself does not need protecting.
- Class 2 biosafety cabinets protect the operator, the product, and the environment, and guard against cross-contamination through HEPA filtration and laminar airflow across the work surface. They are the most widely used cabinet, and the type most of our customers run.
- Class 3 biosafety cabinets are fully enclosed for the highest-risk agents. Filtered air is supplied, the exhaust air is treated so no micro-organisms are released, and the operator works through sealed gloves built into the front.
Meeting the right standard
Once you have settled on a class, the cabinet has to conform to the standard that applies in your country. In the UK that is BS EN 12469, the performance standard for microbiological safety cabinets, which was revised into a new multi-part edition in 2025. For a Class 2 cabinet, look for:
- Double in-line filters, so each can be tested individually
- H14 or higher grade filters
- Access ports that allow the whole filter, seals, and gaskets to be tested
- A front aperture of 160 to 250mm
- The cabinet marked to the relevant standard
BS EN 12469 also sets the inward airflow velocity, in the range of 0.25 to 0.50 metres per second, which is one of the values a test engineer confirms. Outside the UK and Europe, the equivalent North American standard is NSF/ANSI 49, so a cabinet certified to one is not automatically certified to the other.
Other factors when buying
The class and standard settle the safety performance, but a few practical choices shape how well the cabinet suits your lab. Construction materials matter, because 304 or 316 stainless steel resists most chemicals but can pit with certain aggressive substances, while polypropylene is chemical-resistant, non-corroding, and lighter. Size and clearance matter too, since the footprint has to fit the space, allow room to work, and sit clear of features such as electrical outlets. Consider the base and working height, so operators can sit or stand comfortably, and weigh the running costs, energy use, filter life, and warranty, rather than the purchase price alone.
Where to site the cabinet
Where you place the cabinet is part of its safety, because movement and air currents nearby disturb the inward airflow it depends on. In the UK, BS 5726 sets out the minimum distances from anything in the lab that could disturb the work. A few examples:
- Cabinet to traffic routes: 1m
- Cabinet to a work bench opposite: 1.5m
- Aperture to the opposing wall: 2m
- Two cabinets facing each other: 3m
- Door openings: 1.5m behind the cabinet, 1m alongside it
Validating and testing a biosafety cabinet
On top of general maintenance, a biosafety cabinet needs regular testing to prove it is still running safely and effectively. To protect the test engineer, the cabinet should be thoroughly decontaminated before any of the following are carried out:
- Airflow testing. The direction of airflow is proved with smoke visualisation, with every point showing an inward flow, and the air velocity and volume are calculated.
- HEPA filter testing. An aerosol generator is used to find any damage or leaks in the filters.
- KI discus test. This potassium iodide test measures how well the cabinet contains a biohazard, dispersing particles inside and measuring how many escape through the cabinet's air curtain, which is a direct measure of operator protection.
- Particle count. A particle count is not always required, but where it is needed it must be done before the KI discus test.
This testing is exactly the kind of work covered by our cleanroom validation service, and the WHO's monograph on biological safety cabinets is a solid free reference on how these devices work and are certified.
How often should a biosafety cabinet be tested?
A biosafety cabinet should be tested at least once a year, and additionally whenever the filters are changed or internal parts are maintained. Because our customers largely run Class 2 cabinets, many prefer to have them tested every six months, which keeps the interval well inside the annual minimum and catches any drift early. Consistent testing sits alongside routine maintenance as the two things that keep a cabinet safe over its working life.
Frequently asked questions
A biosafety cabinet is the primary engineering control used to handle hazardous biological materials safely, using HEPA filtration and controlled airflow to protect the operator, the product, or the environment, depending on its class. It contains the viruses, bacteria, and aerosols that would otherwise escape into the room.
There are three classes: Class 1 protects the operator and environment but not the product, Class 2 protects the operator, product, and environment, and Class 3 is fully enclosed for the highest-risk agents. The class you need is set by the biohazard risk of the materials you handle.
In the UK, biosafety cabinets are covered by BS EN 12469 for performance and by BS 5726 for siting and use, and the performance standard was revised into a new multi-part edition in 2025. The North American equivalent is NSF/ANSI 49, so certification to one does not carry across to the other.
A biosafety cabinet should be tested at least once a year, and also whenever its filters are changed or internal parts are maintained. Many operators running Class 2 cabinets choose a six-monthly interval to catch any loss of performance sooner.
A KI discus test is a potassium iodide operator-protection test that measures how well a cabinet contains a biohazard. Particles are dispersed inside the cabinet, and the number escaping through its air curtain is measured, giving a direct reading of the protection it offers the operator.
By Tony Horsfield, director and CEO of ISO Cleanroom and a registered CTCB(I) cleanroom testing professional.
