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Class II Biological Safety Cabinet

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The Class II Biosafety Cabinet is mainly used for handing pathogenic biological samples or for applications that require a sterile work zone. A biological safey cabinet is designed to have: an inflow for protecting the operator, an ULPA/HEPA-filtered downflow which creates an ISO Class 3 work surface that prevents cross contamination for protecting the sample, and an ULPA/HEPA-filtered exhaust for protecting the environment. These cabinets are further classified by 2 standards: EN 12469:2000 and NSF 49.

EN 12649

EN 12649

EN 12469: 2000 Biotechnology - Performance criteria for microbiological safety cabinets is the new harmonized European standard for microbiological safety cabinets, published by CEN, the European Committee for Standardization. This standard classifies BSCs into to Class I, Class II, and Class III.



The NSF International (formerly The National Sanitation Foundation) Biological Safety Cabinetry Program was initiated during the 1970s at the request of the regulatory community, including the Centers for Disease Control (CDC), National Institutes of Health (NIH), and the National Cancer Institute (NCI). This standard further classifies Class II Biosafety Cabinets according to subtypes based on air circulation: Class II Type A1, Class II Type A2, Class II Type B1, and Class II Type B2.

Must-have features to consider:

  • Certified to NSF 49, EN 12469
  • Options for side panel construction
  • Choice of multipiece or single-piece worktrays
  • Equipped with DC-ECM blower for 70% energy savings compared to AC motor
  • Offers a broad range of sizes to fit any available laboratory space
  • Has stable and self-compensating airflow, despite building voltage fluctuations & filter loading
  • UV lamp for decontamination
  • Airflow sensor to alert the user if airflow is sufficient for greater safety
  • Alarm for unsafe sash conditions
  • Ergonomically-designed raised arm rest helps prevent grille blocking and create a comfortable working posture
  • Isocide™ powder coat that inhibits microbial growth

Class II Type A2 Airflow Diagram

Class II Type A2

The Class II Type A2 biological safety cabinet is the most common Class II cabinet. It has a plenum from which 30% of air is exhausted, and 70% re-circulated to the work area as the downflow.

Stated from NSF/ ANSI 49:2010, both the Class II Type A1 and Type A2 must have the positively-pressurized contaminated plenum to be surrounded by negative pressure. In case there is a leakage on the positive plenum, the leaking aerosol will be pulled by the negative pressure back to the positive plenum, and it will not leak out.

In the A2 cabinet, about 70% of air from the positive plenum is recirculated as downflow, and the remaining 30% is discharged to the lab through the exhaust filter.

Class II Type B1 Airflow Diagram

Class II Type B1

The Class II Type B1 biological safety cabinet has a common plenum from which 70% of air is exhausted, and 30% re-circulated to the work area as the downflow. This cabinet also have a dedicated exhaust feature that eliminates re-circulation when work is performed towards the back within the interior of the cabinet. Toxic chemicals employed as an adjunct to microbiological processes should only be allowed if they do not interfere with work when re-circulated in the downflow.

Class II Type B2 Airflow Diagram

Class II Type B2

The Class II Type B2 biosafety cabinets are suitable for work with toxic chemicals employed as an adjunct to microbiological processes under all circumstances since no re-circulation occurs. In theory, Type B2 biological safety cabinets may be considered as the safest of all Class II BSCs since the total exhaust feature acts as a fail-safe in the event that the downflow and / or exhaust HEPA filtration systems cease to function normally. However, Class II Type B2 biosafety cabinets require large laboratory spaces due to its installation system and will require elaborate ducting works.

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