Class II Type A1 BSC Characteristics
二级A1型生物安全柜特性

Exhaust approximately 30% of total air handled and recirculate 70% in cabinet
30%外排，70%内循环

Minimum inflow air velocity is 75 fpm (0.38 m/s) through the front opening

May exhaust HEPA filtered air back into the room or through a canopy (to the outdoors)

Audiovisual alarm required when connected to a building exhaust system

May have contaminated ducts and plenums under positive pressure to the room 
Type A1 cabinets are not suitable for work with volatile toxic chemical and volatile radionuclides.