1. Class II biological safety cabinet Class II biological safety cabinet is also known as laminar biological safety cabinet. The difference from the industrial biological safety cabinet is that the incoming air is first filtered by HEPA to ensure that the air on the covered surface is sterile, not only providing personal protection, but also protecting the sample from contamination. Class II biosafety cabinets are divided into two types, Class II A and Class II B, and can be further subdivided into Class II A 1 and Class II A 2 Class II B 1 and Class II B2. Level II biosafety is self-inhibiting. 70% of the flowing air can be recycled and reused. This biosafety cabinet is suitable for cell or tissue culture and exposure to Class 2 to 3 hazard class pathogens. If positive pressure protective clothing is worn, it can be used in Class II biosafety cabinets to engage with Class 4 hazard class infection factors.
(1) Class II A type biological safety cabinet Class II A type biological safety cabinet (Fig. 1) has a built-in fan to set the laboratory air to 0.38 m/s.
The rate is drawn into the safety cabinet, passing through the HEPA filter and down, at a distance of 6.18 cm from the surface of the table, half through the front row of style grids and the other half through the rear row of style grids. The aerosols or droplets produced in all experiments were carried away by the downward flow. The airflow passes through the discharge passage to the two HEPA filters at the top of the safety cabinet. At this time, about 70% of the gas is returned to the operating area in the cabinet through the supply HEPA filter, and the remaining 30% of the gas is passed through the exhaust filter. It is then discharged to the laboratory and reused, or discharged to the outside through the building's exhaust system.
(2) Outer Exhaust Class II A2, B1, and B 2 biosafety cabinets Exhaust air Class II A2, B1, and B 2 biosafety cabinets are all changed from Class II A1 biosafety cabinets. These biosafety cabinets have their own characteristics (see Table 2), including the speed of air intake from the opening, the amount of air recirculated on the work surface, the amount of air discharged from the cabinet, the air exhaust system of the safety cabinet, and the pressure device. Other biosafety cabinets can be used for different experimental purposes (Table 1).
The difference between Type A and Type B biosafety cabinets is that the amount of circulating gas and exhaust gas covering the surface of the table is different, and the discharge system is different. Detailed materials can be obtained from the manufacturer's instructions (Figure 2).
2. Class III Biosafety Cabinet Class III Biosafety Cabinet (Figure 4) The entire environment is completely enclosed. The incoming gas is filtered by HEPA and the vented gas is filtered through 2 layers of HEPA. There is a special system that maintains a pressure of 124.5Pa in the cabinet and is under negative pressure, providing the best personal protection for the operation of Class 4 dangerous pathogens. During the experiment, two operators can carry the hand into the glove box for operation. A transfer box with a HEPA filter exhaust unit that can be sterilized is located next to the cabinet. There is a chemical immersion box under the cabinet. The safety cabinet can be connected to the double-door autoclave, accept the sterilized items and remove the used materials from the safety cabinet for sterilization. Several glove boxes can be joined together to increase the work area. Class III biosafety cabinets are suitable for laboratories with Class III or IV biosafety levels.
3. Ventilation connection of biological safety cabinets Class II A1 and A2 type external biological safety cabinets have a "casing type" or "umbrella hood type" connection. The casing is installed on the exhaust duct of the safety cabinet, and the gas discharged from the safety cabinet is introduced into the exhaust system of the building. An opening with a diameter difference of 2.5 cm is left between the casing and the safety cabinet exhaust duct to allow the air in the laboratory to be drawn into the building's exhaust system. The building's ventilation capacity must meet the requirements of the air in the room and cabinet. The casing must be detachable or designed to be operationally tested for the biosafety cabinet. Often, fluctuations in building airflow do not have a significant impact on the function of the casing-connected biosafety cabinet.
Class II B1 and B2 biosafety cabinets are securely connected to the building's exhaust system, or preferably to a dedicated exhaust system, through a rigid pipe, ie without any openings. The exhaust air volume and static pressure of the building exhaust system must be exactly the same as those specified by the manufacturer. Certification of hard-pipe-connected biosafety cabinets is more time consuming than recycling bioreactors that return air to the room or to the casing.
4. Selection of biosafety cabinets When purchasing biosafety cabinets, consideration should be given to whether the bioprotective effects provided are for individual operators or for experimental samples; if protection for operators should be clear for pathogenic microorganisms or for toxic chemicals Or both. If it is for pathogenic microorganisms, the biohazard level of the microorganism should also be emphasized; if it is for toxic chemicals, it can be selected according to the following principles: No volatile or toxic chemical substances are handled in the industrial grade or Class II A biosafety cabinet. Class II B1 biosafety cabinets may only be used for the handling of small quantities of volatile or toxic chemicals. For the operation of certain quantities of volatile or toxic chemicals, Class II B2 biosafety cabinets must be used. Different types of biological safety cabinets have different exhaust characteristics
(1) Class II A type biological safety cabinet Class II A type biological safety cabinet (Fig. 1) has a built-in fan to set the laboratory air to 0.38 m/s.
The rate is drawn into the safety cabinet, passing through the HEPA filter and down, at a distance of 6.18 cm from the surface of the table, half through the front row of style grids and the other half through the rear row of style grids. The aerosols or droplets produced in all experiments were carried away by the downward flow. The airflow passes through the discharge passage to the two HEPA filters at the top of the safety cabinet. At this time, about 70% of the gas is returned to the operating area in the cabinet through the supply HEPA filter, and the remaining 30% of the gas is passed through the exhaust filter. It is then discharged to the laboratory and reused, or discharged to the outside through the building's exhaust system.
(2) Outer Exhaust Class II A2, B1, and B 2 biosafety cabinets Exhaust air Class II A2, B1, and B 2 biosafety cabinets are all changed from Class II A1 biosafety cabinets. These biosafety cabinets have their own characteristics (see Table 2), including the speed of air intake from the opening, the amount of air recirculated on the work surface, the amount of air discharged from the cabinet, the air exhaust system of the safety cabinet, and the pressure device. Other biosafety cabinets can be used for different experimental purposes (Table 1).
The difference between Type A and Type B biosafety cabinets is that the amount of circulating gas and exhaust gas covering the surface of the table is different, and the discharge system is different. Detailed materials can be obtained from the manufacturer's instructions (Figure 2).
2. Class III Biosafety Cabinet Class III Biosafety Cabinet (Figure 4) The entire environment is completely enclosed. The incoming gas is filtered by HEPA and the vented gas is filtered through 2 layers of HEPA. There is a special system that maintains a pressure of 124.5Pa in the cabinet and is under negative pressure, providing the best personal protection for the operation of Class 4 dangerous pathogens. During the experiment, two operators can carry the hand into the glove box for operation. A transfer box with a HEPA filter exhaust unit that can be sterilized is located next to the cabinet. There is a chemical immersion box under the cabinet. The safety cabinet can be connected to the double-door autoclave, accept the sterilized items and remove the used materials from the safety cabinet for sterilization. Several glove boxes can be joined together to increase the work area. Class III biosafety cabinets are suitable for laboratories with Class III or IV biosafety levels.
3. Ventilation connection of biological safety cabinets Class II A1 and A2 type external biological safety cabinets have a "casing type" or "umbrella hood type" connection. The casing is installed on the exhaust duct of the safety cabinet, and the gas discharged from the safety cabinet is introduced into the exhaust system of the building. An opening with a diameter difference of 2.5 cm is left between the casing and the safety cabinet exhaust duct to allow the air in the laboratory to be drawn into the building's exhaust system. The building's ventilation capacity must meet the requirements of the air in the room and cabinet. The casing must be detachable or designed to be operationally tested for the biosafety cabinet. Often, fluctuations in building airflow do not have a significant impact on the function of the casing-connected biosafety cabinet.
Class II B1 and B2 biosafety cabinets are securely connected to the building's exhaust system, or preferably to a dedicated exhaust system, through a rigid pipe, ie without any openings. The exhaust air volume and static pressure of the building exhaust system must be exactly the same as those specified by the manufacturer. Certification of hard-pipe-connected biosafety cabinets is more time consuming than recycling bioreactors that return air to the room or to the casing.
4. Selection of biosafety cabinets When purchasing biosafety cabinets, consideration should be given to whether the bioprotective effects provided are for individual operators or for experimental samples; if protection for operators should be clear for pathogenic microorganisms or for toxic chemicals Or both. If it is for pathogenic microorganisms, the biohazard level of the microorganism should also be emphasized; if it is for toxic chemicals, it can be selected according to the following principles: No volatile or toxic chemical substances are handled in the industrial grade or Class II A biosafety cabinet. Class II B1 biosafety cabinets may only be used for the handling of small quantities of volatile or toxic chemicals. For the operation of certain quantities of volatile or toxic chemicals, Class II B2 biosafety cabinets must be used. Different types of biological safety cabinets have different exhaust characteristics
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