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Hoods and Enclosures LabCulture Biological Safety Cabinets

Labculture Class II Type A2 Biological Safety Cabinet

The Class II Type A2 biological safety cabinet is the most common Class II cabinet. It is also the most common safety cabinet of all the different types available. It has a common plenum from which 30% of air is exhausted and 70% is re- circulated to the work area as the downflow. If trace amount of toxic chemicals are employed as an ad- junct to microbiological processes, Type A2 cabinets should be exhaust ducted. Exhaust HEPA filtration only removes air- borne aerosols including biohazards but not chemical fumes. If larger amounts of vaporizing toxic chemicals are used, a Type B2 cabinets should be used instead. Per the newly released NSF/ANSI 47:2010 standards, Class II Type A2 BSCs must have the positively pressurized contaminated plenum to be surrounded by a zone of nega- tive pressurization. This is in case there is a leakage on the positive plenum. The leaking aerosol will be pulled by the negative pressure back into the positive plenum, to insure capture and containment. 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. The main difference between Type A2 and Type B2 cabinet is that Type B2 cabinets must be operated with an exter- nal blower which exhausts air to the external environment via a dedicated ductwork system. This cabinet is not self- balancing. Its own blower can only create down flow and the cabinet relies on an external blower to create flow in the discharge stream. In the Class II Type B2 cabinet all inflow and downflow air is exhausted after HEPA filtration to the external environment without recirculation within the cabinet. Type B2 cabinets are suitable for work with toxic chemicals employed as an ad- junct to microbiological processes. Under all circumstances since no recirculation occurs. In theory, Type B2 cabinets may be considered the safest of all Class II biological safety cabinets since the total exhaust feature acts as a fail-safe in the event that the down flow and/or exhaust HEPA filtration systems cease to function normally. However, Class II Type B2 cabinets are, in practice, more difficult to install, balance and maintain.

Dynamic air barrier, where inflow and downflow converge

Side capture zones

ULPA-filtered air Unfiltered/potentially contaminated air Room air/Inflow air

Labculture Class II Type B2 Biological Safety Cabinet

Dynamic air barrier, where inflow and downflow converge

Side capture zones

ULPA-filtered air Unfiltered/potentially contaminated air Room air/Inflow air

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