Class II B2 Biosafety cabinets feature downflow air drawn from within the laboratory . No downflow air is drawn from the cabinet exhaust air. All downflow and inflow air is exhausted through a HEPA filter without recirculation within the cabinet. All contaminated ducts and plenums are maintained at negative pressure. The Type B2 Biosafety Cabinet may be used for work with volatile toxic chemicals and radionuclides as required as adjuncts to microbiological studies.