Biological laboratories use biological safety cabinets to provide double protection for samples and staff when handling infectious experimental materials such as primary cultures, bacterial strains, and diagnostic specimens. According to the design structure of the airflow and isolation barrier, the biological safety cabinets are divided into class I, II, and III.
 
Class Ⅱ biological safety cabinet is currently the most widely used type. The clean air flow through the high-efficiency filter blows down from the top of the safety cabinet vertically, passes through the working area, and is captured before reaching the breathing area of the staff. The airflow will be filtered before emptied. All classⅡbiological safety cabinets can provide protection for workers, the environment and products.
 
Class Ⅱ biological safety cabinets are divided into four types: A1, A2, B1, and B2 according to the proportion of the exhaust airflow to the total flow of the system and the internal design structure. Class Ⅱ B2 biological safety cabinet, also called "full row" type, is an indispensable furniture for PCR laboratory.
 
The parameters of B2 biological safety cabinet are as follows:
1. The minimum flow rate of the airflow into the front window operation port is 0.5m/s.
2. All the downward airflow in the cabinet is supplied from outside the cabinet, that is, the gas discharged from the safety cabinet is no longer recycled.
3. The airflow inside and outside the cabinet is filtered and then discharged into the atmosphere, and it is not allowed to enter the safety cabinet to circulate or flow back to the laboratory.
4. All contaminated parts should be under negative pressure or surrounded by negative pressure area.
 
Class II biological safety cabinets are widely used in medical and health, disease prevention and control, food hygiene, biopharmaceuticals, environmental monitoring, and various biological laboratories. Only a qualified biological safety cabinet that has been tested by a third-party biological safety cabinet can provide better protection for samples and personnel.