BSCs are distinct from other safety enclosures. Fume hoods pull air over the work item and into the environment through a vent, whereas controlled atmosphere glove boxes are completely enclosed, protecting both users and samples through an airtight barrier. A distinguishing component of BSCs is their use of high-efficiency particle air (HEPA) filters, which scrub effluent between 99.5 percent and 99.99 percent of airborne particles, or at least 99.97 percent of particles larger than 3 microns.

Class I BSCs protect personnel and the environment only. Samples are vulnerable because workspace air is swept over them before filtration and venting. Class II cabinets represent a broad category, with varying capabilities that are further subdivided into categories A1, A2, B1 and B2. The main differentiator between Class I and Class II BSCs is that Class II cabinets employ a HEPA-filtered, vertical, unidirectional airflow within the work area. Class III BSCs, which provide the highest level of protection to workers and samples, are reserved for highly contagious or virulent biological samples.

Class II A2 cabinets are by far the most common BSCs in use today, comprising about 95 percent of installations, according to David Phillips, technical applications specialist at Thermo Scientific (Asheville, NC).

An ongoing controversy for specifying certain Class II cabinet types involves NSF Standard 49, which states that Class II A2 and B2 cabinets are designed to handle “minute” amounts of toxic chemicals and radionuclides. “But nobody has defined the term ‘minute’ quantitatively,” admits Phillips, who works on the NSF joint committee that determines BSC specifications.

To satisfy whatever that requirement might be, and to err on the side of caution, most laboratories automatically specify the use of Class II B2 cabinets, which Phillips describes as “complex… and 10 times trickier to run” than Class II A2 cabinets. “A lot of people get stuck with B2s, but half of them should never have been installed. Users would be much better served by canopied A2 cabinets.”

Jim Hunter, senior project engineer at Labconco (Kansas City, MO.), suggests using B-type cabinets in situations where workers are consistently working with volatile toxic agents, isotopes or anticancer drugs that they don’t want coming back into the lab. Otherwise, the associated costs are simply not worth it. “B cabinets cost a lot of money and use a lot of energy,” says Hunter. “Unfortunately, architects assume a B cabinet is always better because it’s more expensive or because the letter ‘B’ comes after ‘A’ in the alphabet. All too often they simply override a customer’s decision on which type of cabinet to purchase.”

An improvement in operating costs and eco-friendliness is energy consumption. Oldermodel BSCs were energy hogs, but today’s units are downright miserly. However, unlike other laboratory products, purchasers of BSCs must perform their own due diligence, as no third-party organizations provide energy-efficiency ratings for cabinets.

Purifier® Cell Logic®

• Scope-Ready™ feature allows a customer-supplied microscope to be integrated into the cabinet
• Pure-Vu™ Seal allows a clear view into the cabinet
• Features a Stand-Still Isolation Platform which reduces vibration up to 300%
• Temp-Zone™ option keeps heated or chilled samples at their ideal temperatures


1300 Series A2 BSC

• Uses a smaller aperture to extend the life of the HEPA filters by 20 percent
• SmartFlow™ airflow compensation system maintains a safe environment for the user
• Low airflow requirements can reduce noise levels to as low as 62 dB(A)
• Requires only 180 watts to operate

Thermo Fisher Scientific


• Uses dual ULPA filters with 99.999% efficiency for particle sizes between 0.1 to 0.3 microns
• Features a raised airflow grille to maintain safety by preventing blockage
• Features a frameless sash for easy cleaning
• ISOCIDE™ antimicrobial coating on all surfaces minimizes contamination


LabGard ES (Energy Saver)

• Features DC/ECM motor to consume less energy, minimize vibration and lower noise output
• Includes HEPEX Zero Leak Airflow System to ensure uniform airflow and proper filter loading
• Made of 16 gauge type 304 stainless steel as a single piece shell, eliminating leaks
• Choice of three control panel options, all with TouchLink LCD touch screen controls