Guidance on the selection of biosafety cabinets 1/2

1. Class II biological safety cabinet
Class II biosafety cabinet is also called laminar flow biosafety cabinet. The difference with the industrial level biosafety cabinet is that the entry
After HEPA filtration, the air on the table top is sterile, which not only provides personal protection, but also protects the sample from contamination. Class II biosafety cabinets are divided into Class II A and Class II B, and can be further divided into Class II A ₁, Class II A ∈ Class II B ∈, and Class II B .Class II biosafety is self repressing. 70% of the flowing air can be recycled repeatedly. This kind of biosafety cabinet is suitable for cell or tissue culture and the operation of contacting with pathogens of risk level 2~3. If you wear positive pressure protective clothing, you can be engaged in the operation of contacting infection factors of risk level 4 on the Level II biosafety cabinet.
(1) Class II Type A Biological Safety Cabinet
Class II Type A biological safety cabinet (Figure 1) has a built-in fan to control the laboratory air at 0.38 m/s
The safety cabinet is sucked in at a rate of 6.18 cm from the surface of the worktable, and then downward through the HEPA filter. Half of the cabinet passes through the front exhaust grille, and the other half passes through the rear exhaust grille. All aerosols or droplets generated in the experiment are taken away by the downward airflow. The air flow reaches between the two HEPA filters on the top of the safety cabinet through the exhaust channel. At this time, about 70% of the air is returned to the operation area in the cabinet through the air supply HEPA filter for reuse, and the remaining 30% of the air is discharged to the laboratory for reuse after passing through the exhaust filter, or discharged to the outside through the building's exhaust system.
(2) Exhaust air class II
The external air exhaust of A2 type, B1 type and B2 type biosafety cabinets Grade II A2 type, B1 type and B2 type biosafety cabinets are all changed from Grade II A1 type biosafety cabinets. These biosafety cabinets have their own characteristics (see Table 2), including the speed of absorbing air from the opening, the amount of air recycled on the worktable, the amount of air discharged from the cabinet, the exhaust system of the safety cabinet, and the pressure device. Different types of biosafety cabinets can be used for different experimental purposes (Table 1).
The difference between Class II biosafety cabinets Type A and Type B is that the amount of circulating gas and exhaust gas covering the surface of the workbench is different, and the exhaust system is different. The detailed materials can be obtained from the manufacturer's instructions (Figure 2).
2. Class III biological safety cabinet
The whole environment of Class III biosafety cabinet (Figure 4) is * sealed, and the gas entering is filtered by HEPA and discharged
The outlet gas is filtered by 2-layer HEPA. There is a special system to keep the pressure in the cabinet at 124.5Pa, in a negative pressure state, which can provide personal protection for the operation of pathogens with level 4 risk. During the experiment, 2 operators can stretch their hands into the glove box for operation. A transfer box equipped with HEPA filter exhaust device that can be sterilized is equipped beside the cabinet. There is a box soaked in chemical disinfectant under the cabinet. The safety cabinet can be connected with a double door autoclave to receive sterilized items and remove the used materials from the safety cabinet for sterilization. Several glove boxes can be connected together to increase the working area. Class