Analysis of several misunderstandings of biological safety cabinets and safety problems

Misunderstanding 1: Clean bench instead of biosafety cabinet

After investigations in the province, there are still many still using clean benches. Many operators think that the two devices have the same shape and the same effect. They think that the samples they operate are ordinary samples and do not have high performance. Sick. In fact, there is an essential difference between the biosafety cabinet and the clean workbench. The clean bench will be blown down through the work area through the purifying air of the high-efficiency filter to protect the sample. Since the working area is the positive pressure zone, the airflow overflows through the operating window. It only protects the sample and does not provide protection to the operator and the environment. If the operation contains any known or potentially pathogenic aerosol, it will cause great danger to the operator. The biological safety cabinet is a vacuum cleaning workbench that prevents the operator and the environment from being exposed to harmful aerosols generated during the laboratory. It is a cage for infectious microorganisms, correctly operating the biological safety cabinet, and fully protecting the operator. Sample, working environment. Therefore, biological safety cabinets should be used in clinical tests, diagnosis, pathological analysis, preparation of oncology drugs, and related biomedical research institutes and laboratories.

In 2004, the National Decree No. 424 and the national standard GB19489-2004 clearly pointed out that the biosafety cabinet is the main safety equipment that is indispensable for the protection of workers. Therefore, the situation of replacing the biosafety cabinet with a clean workbench should be changed as soon as possible. Otherwise, it will bring great hidden dangers to the medical staff and experimental researchers. At the same time, for the sake of safety, all medical units and related laboratories should re-evaluate the microbiological risk of the laboratory. If there is potential danger, the original clean workbench should be replaced in time, and the biosafety cabinet should be selected according to different needs.

Misunderstanding 2: Advanced

The biosafety cabinets are not properly selected. According to the structural design, the proportion of ventilation, and the objects and degrees of protection, the biosafety cabinets are divided into Class I, Class II and Class III, and Class II is divided into A2 and B2. Different levels of biosafety laboratories should use different levels of biosafety cabinets, or choose appropriate safety cabinets depending on the type of protection and protection. When operating a small amount of volatile chemical reagents or radionuclides, a Class II B2 biosafety cabinet may be selected; when operating a large number of volatile chemical reagents or radionuclides, a Class II B2 biosafety cabinet must be used. At present, the world wide application is a Class II A2 safety cabinet, which can meet the general purpose, and is also economical from the perspective of energy saving. In actual work, many units believe that equipment selection should have a certain degree of advancement, and often use the B2 type when the A2 type can meet the application, causing many problems. Firstly, the B2 type safety cabinet has a displacement of 1600 cubic meters per hour (the model is different), and the exhaust volume of the ordinary household exhaust fan is about 80 cubic meters per hour. If the room does not have enough replenishment air volume, the safety cabinet cannot work normally. There are many laboratories who have no choice but to open the door to start the machine. This does not meet the requirements of the laboratory. In addition, the indoor air is discharged in large quantities. To ensure that the temperature in the laboratory meets the experimental requirements, the load of the air conditioner and the heater is very large. The laboratory is simply not satisfied, and it also causes waste of energy. Some units are misled by some so-called "new features" when choosing a safety cabinet. For example, the safety front panel with electric front window is a big mistake. Because the safety cabinet is in the absence of a two-way power supply system, if the power supply suddenly fails, the power window cannot be closed, and the leakage of harmful substances will cause pollution; and, whether electric or manual, the operating height is fixed, it can be seen that this electric function does not mean Big and very harmful. The choice of safety cabinet should mainly be considered from the performance of the safety cabinet. For example, the high efficiency filter, air circuit design, alarm device, negative pressure protection and other indicators compare the advantages of the safety cabinet, and should not be misled by the advertisement propaganda.

Misunderstanding 3: There are many problems in the installation of biological safety cabinets

Existing laboratories purchase safety cabinets, usually vacating a small piece of open space in the room, there are many problems, improper installation location, will cause pollution. The sides of the biosafety cabinet should be 30 cm on the sides and the back side, leaving enough space for 30 to 34 cm at the top. To reduce the airflow disturbance and ensure the normal operation of the safety cabinet, the biosafety cabinet should be placed away from the laboratory entrance, doors and windows, and heating. Walk the aisle and avoid the air supply to avoid the disturbance of the airflow inside the cabinet. The room in the bio-safety cabinet must have sufficient air supply volume. The Class II A2 exhaust capacity is about 700-1200 m3/h, and the B2 is 1000-1600 m3/h. Some models are higher, if there is not enough. Supplemental air supply, the room where the biosafety cabinet is located becomes a high negative pressure state, and the biosafety cabinet cannot work normally. After many laboratories purchased the Class II A2 biosafety cabinet, it was considered that the exhaust duct was safer than being discharged indoors. In fact, the biosafety cabinet exhaust outlet has a high-efficiency filter, and the discharged gas is proved to be safe and has no effect on the indoor environment. In addition, the clean air of the indoor comfortable working environment is discharged to the outside, which greatly increases the running cost. In addition to operating dangerous subjects or chemical agents that produce chemical odors, it is safe and feasible to discharge the Class II A2 biosafety cabinets into the room. The Class II A2 biosafety cabinet is hard-wired. This type of connection was previously widely used. When the A2 biosafety cabinet is connected to the exhaust system with an exhaust fan using a closed hard pipe, its safe operation is completely dependent on the exhaust system. If the speed of the exhaust air rises or falls, the imbalance in the biosafety cabinet changes, which will cause serious consequences of polluting the environment and the sample. In the US NSF49:2002 standard, Class II A2 biosafety cabinets are prohibited from using closed pipe connections. If the exhaust body of the Class II A2 safety cabinet is outside, it is recommended that the exhaust duct be connected by a casing. The casing is installed on the exhaust pipe of the biological safety cabinet, and a 2.5 cm gap is reserved between the safety filter and the high efficiency filter of the safety cabinet. The air in the room can also be sucked into the exhaust system of the building. This connection method is * safe connection mode. The airflow balance in the cabinet is independent and the exhaust system. No matter how the exhaust system fluctuates, the airflow balance in the cabinet will not be balanced. affected. Class II B2 must be connected by a rigid pipe to the exhaust system in a sealed manner. The exhaust air volume and static pressure of the exhaust system must be consistent with the requirements of the safety cabinet. When installing multiple Class II B biosafety cabinets, separate exhaust ducts should be used, and the exhaust ducts should not be shared.

Myth 4: There is a biological safety cabinet, everything is "OK"

The use and limitations of the safety cabinet should be explained to each operator, strictly in accordance with the requirements, such as the use of early boot "self-cleaning", the placement of items in the cabinet is reasonable, regular maintenance verification. The biosafety cabinet cannot protect the operator when an operation error or leakage or breakage occurs. The air curtain in front of the biosafety cabinet is fragile and highly susceptible to interference and contamination. In the experiment, the position of the front window cannot be opened at will, the operation is moderate, and the arm avoids frequent access to the safety cabinet to prevent the airflow from being disturbed. When the safety cabinet is working, the switch door, the personnel walking around the room, and even coughing behind the operator will cause turbulence and increase the amount of microbial aerosol spillage, which will cause laboratory pollution. Foreign scholar Oster has reported that the staff used a straw in the safety cabinet to absorb the rickettsia suspension, and the other person was infected with the disease 14 minutes after talking to the cabinet. There are many pollution incidents caused by the violation of operating procedures, inattention, unstable operation, improper operation methods or equipment. A slight improvement in the method of operation or on the equipment, such as withdrawing the needle from the bottle of the rubber stopper, enveloping the mouth of the bottle with an alcohol cotton ball is 99% less than the aerosol that is not produced. Therefore, operators must firmly establish safety awareness, develop good operating habits, eliminate illegal operations, strictly follow microbiological standard operating procedures and biosafety laboratory operating procedures, and use standardized laboratory equipment. Personal protection is the last protection against laboratory aerosol infections. It is usually protected by physical protection and vaccine immunity. Physical protection is mainly for the protection of the respiratory tract and eyes, such as windshields, masks, protective masks, positive pressure helmets and positive Press the overalls and so on. After the biosafety cabinet is put into use, its management is an important task, and it is also a weak link. Due to the unclear responsibility of the equipment personnel and the experimental personnel, it is neglected to manage, which brings great hidden dangers to the laboratory safety. It must be established. The scientific management system is strictly enforced, the responsibility is implemented to the people, and supervision is carried out to ensure the safety of the laboratory.

Myth 5: Biosafety cabinet monitoring becomes blank

Nowadays, biosafety cabinets are widely used in medical and health, disease prevention and control, food hygiene, bio-pharmaceuticals, environmental monitoring, and laboratories at all levels. They are important material foundations for ensuring biosafety and environmental safety, and are classified as “people's livelihood”. category. At present, most users do not know enough about the detection performance of biosafety cabinets. Many users think that as long as the biosafety cabinets can be used, they will continue to be used, which becomes a big hidden danger. However, only a small number of users understand the importance of biosafety cabinets. However, because of the lack of qualified institutions to carry out the testing of biosafety cabinets, it has become powerless. After that, it will not be able to do so. The biosafety cabinet must be re-inspected on site after installation, moving position, after repair, and after replacing the high-efficiency filter. In addition, an annual routine inspection and safety assessment should be performed.