Protecting Workers and the Environment From Biohazards
Biological safety cabinets (BSCs) are enclosures that protect users from biohazards by cleansing the work space air through HEPA filters. By contrast, laminar flow hoods are designed to protect samples from users. The third major type of safety enclosure, the fume hood, vents work space and laboratory air to the environment, usually without filtering it.
The U.S. Centers for Disease Control and Prevention lists three major classes of BSCs: Class 1 protects the user and environment but not the product; Class 2 protects the user, product, and environment; and Class 3 provides the maximum protection from extremely virulent pathogens.
Within Class 2 are four major categories, A1, A2, B1, and B2, which differ in terms of air flow but not degree of protection. A2-type BSCs make up about 90 percent of all units sold in the United States. Users are not likely to keep track of the sometimes fine distinctions between models, but vendors are more than happy to help match workflows with cabinets.
BSCs are to biologists what fume hoods are to chemists, but the two devices work completely differently. Fume hoods, which protect users from chemicals, vent work space and laboratory air to the outside environment; BSCs remove particulates and aerosolized pathogens from the work area through HEPA filtration, then recirculate or exhaust the purified air. Laboratories always choose BSCs for biologics, and fume hoods for chemicals and radionuclides, because exhaust does not nullify pathogens and HEPA filtration does not remove chemicals.
Most of the time, that is. A2 canopy BSCs are a type of hybrid: designed as BSCs, they exhaust rather than recirculate.
What to look for
According to Brian Garrett, product manager at Labconco (Kansas City, MO), ongoing trends in BSCs include improvements in the user interface, cabinet usability, and ergonomics, and lower operating cost.
Motors that run the air-handling systems of BSCs were traditionally of the PSC (permanently split capacitor) type, which are relatively inexpensive but are energy hogs with a relatively short operating life. PSCs also throw off a lot of heat, which increases air conditioning costs and makes workers uncomfortable during long work sessions.
Today, most labs select either an electronically commutated motor running on direct current or a three-phase AC motor. Both designs cost more than a PSC motor but run more efficiently and have an operating life of about 50,000 hours, compared with 10,000- 15,000 hours for a PSC.
Energy-efficient motors don’t just save money on the electricity bill, says John Peters, assistant marketing director at NuAire (Plymouth, MN). “They improve the product.”
HEPA filtration affects operating costs directly. The more life you can get out of the filters, the lower your operating costs. HEPA usable life is based on the torque or reserve capacity of the blower and the size of the HEPA filter. Safety-conscious purchasers tend to go with powerful blowers, but Mr. Garrett urges users to consider energy efficiency as well and balance the two needs, because “otherwise you’re compromising one in favor of the other.”
Ergonomics plays into purchase decisions for BSCs much more so than for fume hoods. Due to the nature of their work, chemists often set up experiments, close the hood sash, and walk away for hours, while biologists spend many hours glued to BSCs. Mr. Garrett suggests that buyers take special note of a BSC’s height, arm support, heat generated from the cabinet (less is better), and internal/external dimensions. The cabinet should be large enough to accommodate all anticipated reagents and equipment, which users should be able to reach comfortably.
John Peters agrees that ergonomics are a prime consideration when selecting BSCs. He adds to the wish-list factors that enhance seating and posture during long work sessions, cabinet layout, and glare-free lighting.
Controls and feedback should be accessible at all times. Preferably, these should indicate key operating and safety parameters constantly, and in real time. “Users need to know the HEPA filter loading, which tells them if the air coming out of the cabinet is safe, on a moment’s notice and not just once or twice a year,” Mr. Garrett tells Lab Manager Magazine.
Unlike most other lab equipment and instrumentation, options on BSCs are often tailored to specific applications and workflows. “A lot of customization goes into cabinets that benefit end users,” Mr. Peters says, “from features and functions to materials of construction.”
The long-term look
Since BSCs last 15 years or more, customers might be concerned about replacement parts. Some vendors keep these on hand, and parts may be salvaged from used cabinets, but “just-in-time” mentality suggests that critical replacement components like motors will probably not be available much beyond normal service life. But according to Mr. Peters, older units may be difficult to service as standards change, “so users will probably want new products with new technology for ergonomic, safety, and cost-saving features.”
Angelo DePalma holds a Ph.D. in organic chemistry and has worked in the pharmaceutical industry. You can reach him at firstname.lastname@example.org.
Biological Safety Cabinets:
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