You will encounter several misconceptions about biological safety cabinets

The biological safety cabinet is used to protect the operator, laboratory environment and experimental materials from exposure to the above-mentioned operation process when handling infectious experimental materials such as primary cultures, bacterial strains and diagnostic specimens. Designed for possible infectious aerosols and splashes.
According to the difference in the level of biological safety protection, biological safety cabinets can be divided into three types: first-class, second-class and third-class. Class I biological safety cabinets protect workers and the environment without protecting samples. Its airflow principle is basically the same as that of a laboratory fume hood, except that the exhaust port is equipped with a HEPA filter to filter the external exhaust flow and prevent contamination caused by the diffusion of microbial aerosols. The first-class biological safety cabinet itself has no fan, and relies on the fan in the external ventilation duct to drive the airflow. Since it cannot protect the products in the cabinet, it is rarely used.
Misunderstanding 1: Clean workbench instead of biological safety cabinet
At present, many hospitals are using a large number of medical clean workbenches. Many operators believe that the two types of equipment have the same appearance and similar functions, and believe that the samples they operate are ordinary samples, which are not highly pathogenic. In fact, there are essential differences between the biological safety cabinet and the clean workbench. The clean workbench will blow the purified air through the high-efficiency filter down through the work area to protect the sample. Since the work area is a positive pressure area, the air overflows through the operation window. , which only protects the sample, but does not provide protection for the operator and the environment. If the operation contains any known or potentially pathogenic aerosols, it will bring great hidden dangers to the operator.
The biological safety cabinet is a negative pressure purification workbench, which can prevent the operator and the environment from being exposed to harmful aerosols generated in the laboratory process, and is a cage of infectious microorganisms. Samples, working environment. Therefore, biosafety cabinets should be used in clinical inspection, diagnosis, pathological analysis, preparation of tumor drugs, and related biomedical research institutes and laboratories in hospitals.
Misunderstanding 2: Advancement
Improper selection of biological safety cabinets. According to the structural design, exhaust ratio and protection objects and degrees, biological safety cabinets are divided into Class I, Class II and Class III, of which Class II is further divided into A2 and B2 types. Different levels of biosafety laboratories should use different levels of biosafety cabinets, and appropriate safety cabinets can also be selected according to different types of protection and protection. When operating a small amount of volatile chemical reagents or radionuclides, you can choose a Class II B2 biological safety cabinet; when operating a large amount of volatile chemical reagents or radionuclides, you must use a Class II B2 biological safety cabinet. At present, the most widely used is the Class II A2 type safety cabinet, which can meet the general purpose of the hospital, and is more economical from the perspective of energy saving. In actual work, many units believe that equipment selection should have a certain advance, and often choose B2 type when A2 type can meet the application, causing many problems. The selection of safety cabinets should be mainly considered from the performance of safety cabinets, such as high-efficiency filters, air duct design, alarm devices, negative pressure protection and other indicators to compare the advantages of safety cabinets.
Misunderstanding 3: There are many problems in the installation of safety cabinets
Existing laboratories purchase safety cabinets, and generally vacate a small space in the room to place them. There are many problems. Improper installation positions will cause pollution. There should be 30 cm on both sides and the back of the biological safety cabinet, and enough space at the top of 30-34 cm; in order to reduce airflow disturbance and ensure the normal operation of the safety cabinet, the biological safety cabinet should be placed away from the laboratory entrance, doors and windows, heating, Aisle, avoid the air supply outlet, to avoid the disturbance of the air flow in the cabinet caused by the external air flow. The room where the biosafety cabinet is placed must have sufficient air supply. The exhaust volume of Class II A2 is about 700 to 1200 m3/h, and that of B2 is 1000 to 1600 m3/h. Some models are higher, if there is not enough air Supplementary air supply, the room where the biological safety cabinet is located becomes a high negative pressure state, and the biological safety cabinet cannot work normally. After purchasing a Class II A2 biological safety cabinet, many laboratories believe that it is safer to connect the exhaust duct to the outside than to the indoor. In fact, the exhaust outlet of the biological safety cabinet is equipped with a high-efficiency filter, and the exhausted gas has been proved to be safe and has no impact on the indoor environment; in addition, exhausting the clean air of the indoor comfortable working environment to the outside will greatly increase the operating cost, so , except for experimental objects with high risk of operation or chemical reagents that can produce chemical odors, it is safe and feasible to exhaust air from Class II A2 biological safety cabinets indoors.
Class II A2 type biological safety cabinet adopts hard connection. This connection method has been widely used before. When the A2 type biological safety cabinet uses a closed hard pipe to connect to the exhaust system with an exhaust fan, its safe operation completely depends on the exhaust system. For example, when the speed of exhaust air increases or decreases, the imbalance in the biological safety cabinet will change, which will cause serious consequences of polluting the environment and samples. Class II B2 must be connected to the exhaust system through a hard pipe, and the exhaust air volume and static pressure of the exhaust system must be consistent with the requirements of the safety cabinet. When multiple Class II B-type biological safety cabinets are installed, separate exhaust ducts should be used for each, and exhaust ducts cannot be shared.
Myth 4: With a biological safety cabinet, everything is "OK"
The use and limitations of the safety cabinet should be explained to each operator and operate strictly according to the requirements, such as the use of "self-cleaning" of early startup, reasonable placement of items in the cabinet, and regular maintenance and verification. The biological safety cabinet cannot protect the operator when there is an error in operation or leakage or breakage occurs. The air curtain in front of the biological safety cabinet is very fragile and can easily be disturbed and polluted. During the experiment, the position of the front window could not be opened at will, the operation movement was gentle, and the arm should avoid frequent entry and exit of the safety cabinet to prevent disturbing the airflow. When working in the safety cabinet, opening and closing the door, people walking in the room, and even coughing behind the operator's back will form turbulent flow and increase the amount of microbial aerosol overflow, resulting in laboratory contamination.
Therefore, operators must firmly establish safety awareness, develop good operating habits, prevent illegal operations, strictly follow the microbiology standard operating procedures and biosafety laboratory operating procedures, and use standardized experimental equipment.