How Class II Biosafety Cabinets Have Advanced: From Simple Boxes to Smart Lab Solutions

Class II biosafety cabinets (BSCs) have evolved from their beginnings. The very first cabinets strived to combine the inflow of a Class I BSC or fume hood with the clean downflow of a vertical flow clean bench. There were variations on the theme until the NIH specified its preferred design in 1974. As manufacturers sought to meet those requirements and other users requested the same thing, the basic form of the Class II BSC as we know it came into being.

But just as we can see the similarities and differences when looking at pictures of friends from elementary or high school, we can see how BSCs have really grown up.

From simple boxes to ergonomic workstations: how BSC design has evolved

Most of the first cabinets were boxes. They had straight vertical fronts, and reaching into the work area was like reaching into a storage cubby. Most modern cabinets have slanted fronts to allow users to shift their position as they work in the cabinet. Even as we sit at desks, we lean forward and back, adjusting our positions as we work. This reduces the stress of maintaining the same position for extended periods of time.

Tabletop designs for placement on stands have become more common. This also improves ergonomics as it is possible to adjust the height of the cabinet and even have electric stands.

Smarter, greener, safer: the rise of advanced motors, filters, and monitoring

The first BSCs used AC motors with unusually inefficient fan speed controls. The average cabinet, with a nominal 4-foot width, drew over six hundred watts, which was as much average energy as an entire apartment. In the 2000s, we started seeing the use of electronic or brushless DC motors, which consumed less than half the energy and opened the door to advanced features such as night setback modes and improved flow compensation.

BSCs need filters and airflows. HEPA filters allow BSCs to capture biological hazards and microbial contamination. The inflow air velocity allows the cabinet to prevent the escape of hazards out the front opening, and the downflow air velocity prevents invading contamination from reaching the cabinet’s work surface. But as filters capture particles and load, they resist the flow of air. HEPA filters and air velocity are both needed, but they resist one another. BSC design has always sought to enable air velocity compensation for filter loading with automatic adjustment of fan speeds.

The early BSCs were able to maintain the total flow through the fan within 10 percent even as the filter resistance across the filters increased by 50 percent. In addition to providing greater energy efficiency, advanced DC motors also enable more sophisticated flow compensation. These modern systems can maintain flow to within 1 or 2 percent.

Finally, modern BSCs let us see what is happening. The containment provided by the airflows and the clean air provided by the HEPA filters are not perceivable without special equipment. Early BSCs might have a light to indicate when the fans were on, though you could tell that by the sound. The actual flow and balance of inflow and downflow were impossible to verify. People would put tissue paper in the front opening to indicate containment, but that only showed that air was moving.

Looking ahead: how BSCs are becoming smarter and more user-friendly

Modern BSCs are moving to full-text alarm notifications and even graphical displays. Instead of an audible alarm with a red light showing a problem with airflow, newer cabinets will tell us whether it is inflow or downflow and if they are too high or too low.

Class II BSCs are great tools that improve laboratory safety and reduce contamination. These tools continue to advance and to serve us better. The future is bright!