Biological Safety Cabinet

A BSC is a device that encloses a workspace in such a way as to protect workers from aerosol exposure to infectious disease agents. Air that contains the infectious material is sterilized, either by heat, ultraviolet light, or, most commonly, by passage through a HEPA filter that removes most particles larger than 0.3 fim in diameter. These cabinets are designated by class according to the degree of biologic containment they afford. Class I cabinets allow room (unsterilized) air to pass into the cabinet and around the area and material within, sterilizing only the air to be exhausted (Figure 4-10). They have negative pressure, are ventilated to the outside, and are usually operated with an open front. Class H cabinets sterilize air that flows over the infectious material, as well as air to be exhausted. The air flows in "sheets," which serve as barriers to particles from outside the cabinet, and direct the flow of contaminated air into the filters (Figure 4-11). Such cabinets are called vertical laminar flow BSCs, Class n cabinets have a variable sash opening through which the operator gains access to the work surface. Depending on their inlet flow velocity and the percent of air that is HEPA-filtered and recirculated, class n cabinets are further differentiated into type A or B. The IIA cabinet is self-contained, and 70% of the air is recirculated. The exhaust air in Class DB cabinets is discharged outside the building. The Class IIB cabinet is selected if radioisotopes, toxic chemicals, or carcinogens will be used. Because they are completely enclosed, with negative pressure, Class in cabinets afford the most protection to the worker. Air coming into and going out of the cabinet is filter sterilized, and the infectious material within is handled with rubber gloves that are attached and sealed to the cabinet (Figure 4-12).

Most hospital clinical microbiology laboratory technologists use Class IIA cabinets. The routine inspection and documentation of adequate function of these cabinets are critical factors in an ongoing quality assurance program. Important to proper operation of laminar flow cabinets is maintenance of an open area for 3 feet (90 cm) from the cabinet during operation of the air-circulating system to ensure that infectious material is directed through the HEPA filter. BSCs

Typical class II biological safety cabinet


Exhaust HEPA filter

Supply HEPA filter--

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Bacterial Vaginosis Facts

Bacterial Vaginosis Facts

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