How Class II Biological Safety Cabinets Work

Understanding Class II Biological Safety Cabinets

Selecting a Class II Biological Safety Cabinet (BSC) requires considering multiple factors including, among others, the materials, quantity, and procedures being performed within the cabinet, the facility requirements based on risk assessments, the location of the cabinet within the laboratory itself, the installation requirements of the cabinet, and the mechanical systems exhaust/supply to both the laboratory and the cabinet.

All of NuAire's Class II BSCs, regardless of type (i.e. A2, B1, or B2) provide the same level of product and personnel protection from a biological point of view. The NSF International Listing Program for compliance, standard NSF/ANSI 49*, has subjected each type to the exact same minimum testing procedures and exactly the same pass/fail criteria for all Class II BSCs. NuAire additionally performs a wide range of dynamic biological challenge tests to assure maximium containment performance.

What then is a key difference between the types of class II biological safety cabinets that affect selection?

The amount of air that is recirculated within the cabinet:

  1. Type A2 cabinets recirculate 70%
  2. Type B1 recirculate less than 50%
  3. Type B2 cabinets recirculate 0% (total exhaust)

If it is determined that a process or procedure must be contained in a Class II BSC (due to biohazard risk or cleanliness requirements), the selection of the cabinet, in our opinion, is based solely on the quantity and the volatiles used in the process/procedure within the cabinet. For all Class II BSCs, EXCEPT the NU-435 Total Exhaust Biological Safety Fume Hood, which has been evaluated by UL and classified to the UL 1805 fume hood standard for use with volatiles, NuAire places a bright red warning label on the face of the cabinet concerning the use of flammables, as follows:


NuAire recognizes, however, that some procedures demand the use of volatiles within a standard Class II BSC. If this is a requirement, the use of volatiles should be reviewed through a risk assemesment process with your facility safety personnel. Volatiles can freely pass through HEPA filtration and if used, require the BSC to be exhausted through either a direct or canopy connection depending upon the cabinet class and type.

To aid in the risk assessment process, reference materials can be found in NuAire general bulletins for Biological Safety Cabinets, NSF/ANSI 49 Annex E, Biosafety in Microbiological and Biomedical Laboratory (BMBL most recent version) and other industry publications.

Once again, if you need additional information, copies of relative information, or links to on-line guidelines please see the reference materials section, call us at the number below, or e-mail us.

NuAire is not qualified to provide proper guidance for selecting, recommending laboratory biosafety levels, selection of engineering controls, or facility requirements.

Join the laboratory professionals that have made NuAire Biological Safety Cabinets the most highly regarded biological safety cabinet in the world.