Guide to Selecting a Biosafety Cabinet

A biological safety cabinet—also known as a biosafety cabinet or BSC—provides a ventilated workspace for performing experiments and procedures. In all BSCs, protecting scientists in the lab is the top priority. Some BSCs also protect samples. The right BSC depends on the job.

To select the best BSC for a lab, a scientist needs to know how it will be used, including the biological agents that might be handled. The 6^th edition of Biosafety in Microbiological and Biomedical Laboratories (BMBL) describes the needed biosafety level for specific agents. In brief, this document states:

• Biosafety Level 1 (BSL-1) is needed when working with “defined and characterized strains of viable biological agents that are not known to cause disease in immunocompetent adult humans”
• Biosafety Level 2 (BSL-2) is required with “moderate-risk agents that cause human disease of varying severity by ingestion or through percutaneous or mucous membrane exposure”
• Biosafety Level 3 (BSL-3) is necessary for “agents with a known potential for aerosol transmission, for agents that may cause serious and potentially lethal infections, and that are indigenous or exotic in origin.”
• Biosafety Level 4 (BSL-4) is used when scientists work with exotic agents “that pose a high individual risk of life-threatening disease by infectious aerosols and for which no treatment is available.

To simplify picking the BSL for a lab, turn to Stanford University’s Biosafety Levels for Biological Agents. Just go to this page, search for an agent’s name and then note the required BSL. For example, E. coli is a BSL-2 agent and Tick-Borne Encephalitis Complex requires BSL-4 working conditions. After finding the BSL needed for a project, the type of BSC can be selected.

Image: Any biosafety cabinets requires testing—as shown in this 1964 inspection at the Center for Disease Control and Prevention. Image from CDC/James A. Johnson.

Categories of BSCs

For an overview of BSCs, see Biocompare’s page on Class I, II, & III Biosafety cabinets. Here’s a quick comparison of the BSC categories:

• Class I: These BSCs can be ducted or ductless and protect the user and the lab environment, but not the sample. A Class I BSC can be used for containment in BSL 1, 2, or 3 applications.
• Class II: These BSCs perform the tasks of Class I plus sample protection. They include several subcategories: Type A1, Type A2, Type B1, and Type B2. The distinguishing features of these types, as noted on the Biocompare page, “are their minimum inflow velocities and exhaust systems.”
• Class III: These BSCs, sometimes known as gloveboxes, are completely enclosed and can be used in BSL 1–4 applications.

For more details on BSCs, see the NSF International Standard/American National Standard (NSF/ANSI) 49 – 2019 on Biosafety Cabinetry: Design, Construction, Performance, and Field Certification.

Purchasing pointers

In all applications, a BSC purchase benefits from research plus professional input. As NSF/ANSI 49 – 2019 notes: “A biosafety professional should be consulted prior to a biosafety cabinet (BSC) purchase. Some institutions have BSC purchases approved by the biosafety professional after consultation with the user, architect, and engineer.”

To make the best BSC selection, many factors should be considered. For one thing, the BSC must open enough to provide the access needed for a given application and still keep lab personnel safe, but look carefully when assessing that information. “Question any manufacturer touting both a tested and then a working access opening,” says Seth De Penning, product marketing manager at NuAire.” Why would two such numbers even be reported? As De Penning says: “Think about it—why would you ever use the cabinet at an access height other than the one at which it was tested for biocontainment?” If a BSC is only safe when the sash is open a few centimeters, that’s not the right fit for many—if any—applications.

A BSC purchase decision also requires balance. As De Penning notes: “Recognize the importance of energy efficiency, but take a holistic approach.” He adds, “If the cabinet claims ultra-low energy consumption but has a lower inflow velocity and/or a smaller work access opening, it might be underpowered.” A BSC should make the most of the energy needed to perform the required task. It’s not effective if a BSC improves energy efficiency at the expense of performance, such as creating a more difficult reach into the work zone, a weaker air barrier, or limited thrust to push through an increasingly saturated HEPA filter over the long term. “Think about it like your car: Your hybrid is great for summer driving in the city, but can you tow your trailer to the mountains in the winter?” De Penning asks. “There are tradeoffs.” As an example, he says, “If the cabinet doesn’t have enough thrust to compensate filter saturation, the energy savings may be partially offset by more filter changes that tend to be costly.”

Simplify BSCs by staying basic

As shown by the BSLs and BSC categories and types, it’s easy to get caught up in the complexity of this range of products, but that’s not necessarily productive. “Keep it simple and get back to basics,” De Penning says. “Before considering bells and whistles, consider what adds value in terms of improving protection and continuing to offer that protection cost-effectively and ergonomically over the long-term.”

Just making a BSC different doesn’t make it better. As De Penning puts it: “There is a lot of differentiation for differentiation’s sake, but differentiation only adds value if it helps the cabinet perform its fundamental purpose of helping you perform your work more safely and more effectively than other cabinets in the market.”