Biosafety Cabinets (BSCs) are ventilated enclosures for containing biohazard work assigned to Biosafety Levels 1 through 4 as described in the BMBL (CDC, 2009). These enclosures or Primary Engineering Controls (PECs) are categorized into three Classes depending on the type of protection offered. Class II offers three types of protection: Personnel, Product, and Environmental. Within this classification are four types of BSCs. Type A cabinets are internally recirculating cabinets, with Type A1 and Type A2 differing on their minimum intake velocity of air. Type B2 cabinets exhaust 100% of all the air passing through the cabinet to the outdoors. Type B1 cabinets have both recirculation and direct exhausting capabilities. The different styles of BSCs create their protection through the use of HEPA (High Efficiency Particulate Air) filters.