Know Your BSC: How to Identify and Use Biological Safety Cabinets on Campus

What is a biological safety cabinet? Biological safety cabinets (BSC) are partial barrier systems that rely on air movement to provide personnel, environmental and product protection. The cabinets themselves have been designed to increase or modify how they protect each element, and are an important safety component of certain research and laboratory environments

On the UW–Madison campus, the vast majority of BSCs were manufactured by The Baker Company of Sanford, Maine. Baker cabinets are considered as one of the best-designed and well-built cabinets in the research community. As renowned and effective as they are—not all cabinets are alike. There are 4 types of BSCs on campus with specified uses for different scenarios. Read on to learn about and quickly identify each type of BSC on campus.

What do the stickers mean?

When looking at a BSC, you may notice a red, white, and black sticker in the upper left-hand corner of the cabinet. These stickers have been placed to help you identify the type of the cabinet, and what procedures may be done inside the HEPA filtered work area.

Class II-A2

The most common type of cabinet on campus is the Class II-A2.

This sticker appears on the Class II-A2 BSC

Class II-A2 biological safety cabinets range in size from 3 to 6 feet in width. Comprised of a stainless steel work area, safety laminated view screen, a motor and 2 HEPA filters, they are the choice of many labs.
Personnel and product protection is provided by a combination of inward and downward airflow.
Environmental protection is provided by exhaust air being discharged through a HEPA filter. Because many of these cabinets discharge the clean air back into the lab, they are not intended to be used with hazardous chemicals.

Class II-A2 Canopy Connected (“FlexAir”)

For the users who need to use chemicals in their research, the Class II-A2 Canopy Connected BSC option is available.

This sticker appears on the Class II-A2 Canopy Connected “FlexAir” BSC

This BSC uses the same A2 cabinet with an optional exhaust transition (and is referred to as a FlexAir).
It connects the exhaust HEPA filtered air to the building exhaust and allows chemical fumes to be exhausted outside the lab and building.

In the event a building exhaust system loses volume, an alarm is sounded at the cabinet allowing the user to stop their work safely. The cabinet will continue to operate but a flap is opened on the front of the FlexAir and HEPA exhaust air is circulated back into the lab. Upon normal building exhaust being reinitiated, the alarm will stop and the front flap closes allowing the user to go back to using small amounts of chemical in the work area.

Class II-B1

In the event that a lab needs to use more chemicals in their research than allowed by Chemical Safety in an A2 model, the BSC for this use is a model referred to as an NCB Class II B1.

This sticker appears on the Class II-B1 BSC

This biological safety cabinet exceeds specifications developed by the National Cancer Institute with features to enhance containment while inhibiting cross contamination and exposure to chemicals, vapors and gases.

The Class II-B1 model is also connected to the building exhaust and features safety alarms for user protection, in addition to a safety feature that completely shuts the cabinet off when a 20% reduction of building exhaust is detected.

Clean Air Device

The final example of the BSC is not a BSC. It is called a Clean Air Device.

This sticker appears on the Clean Air Device

This laminar flow clean bench allows HEPA filtered air to flow across the work surface. This does not protect the user as it only prevents contaminated room air from entering the work area.

A Clean Air Device should never be used when working with infectious material or toxic chemicals.

How are biological safety cabinets certified and repaired?

A team from the UW–Madison Office of Biological Safety, a department of EH&S, takes care of all BSC certification and repair on campus so that PIs, Lab Managers and students can concentrate on research. UW–Madison is one of a few universities in the country that has a dedicated team to certify and repair all biological safety cabinets for the entire campus.

For more information and services please contact the Biological Safety Cabinet Program at or 608-262-1809.

It’s Biosafety and Biosecurity Month 2021! Learn about the latest biological safety updates that impact labs like yours on the UW–Madison campus, and get the poster to help spread the word.

The Office of Biological Safety is a proud member of the American Biological Safety Association (ABSA).