Views: 9 Author: Site Editor Publish Time: 2020-08-28 Origin: Site
According to the differences in the level of biological safety protection, biological safety cabinets can be divided into three types:Class I,Class II and Class III. Class I biological safety cabinet can protect staff and the environment without protecting samples. The air flow principle of the laboratory fume hood is basically the same. The difference is that the exhaust port is equipped with a HEPA filter to filter the external exhaust flow to prevent the spread of microbial aerosols and cause pollution. The first-level biological safety cabinet has no fan, and relies on the fan in the external ventilation pipe to drive the airflow.
Class II biological safety cabinet is currently the most widely used cabinet type. According to the provisions of "The People's Republic of China Pharmaceutical Industry Standard YY0569-2011 Biological Safety Cabinets", Class II biological safety cabinets can be divided into 4 levels according to the inlet air velocity, exhaust mode and circulation mode: Type A1, Type A2, Type B1 And type B2. All Class II biological safety cabinets can provide protection for workers, the environment and products.
The minimum air velocity or the measured average value of the front window of the Class II A1 safety cabinet shall be at least 0.38m/s. 70% of the gas is recirculated to the work area through the HEPA filter, and 30% of the gas is filtered out through the exhaust port.
The minimum airflow velocity or the measured average value of the front window of the Class II A2 safety cabinet should be at least 0.5m/s. 70% of the gas is recycled to the work area through the HEPA filter, and 30% of the gas is filtered out through the exhaust port.
The Class II B biological safety cabinets are all safety cabinets connected to the exhaust system. The fan connected to the exhaust duct of the safety cabinet is connected to the emergency power supply, so that the negative pressure of the safety cabinet can be maintained even when the power is cut off, so as to prevent dangerous gas from leaking out of the laboratory. The minimum air velocity of the front window or the measured average value should be at least 0.5m/s (100fpm).
Class II B1 70% of the gas is removed through the exhaust port HEPA filter, and 30% of the gas is recirculated to the work area through the supply port HEPA filter.
Class II B2 is a 100% full row safety cabinet with no internal circulating air flow. It can provide both biological and chemical safety control. It can operate microbiological experiments with volatile chemicals and volatile nuclear radiation as additives.
Class III biological safety cabinet is designed for laboratories with a biological safety protection level of level 4. The cabinet is completely air-tight, and the staff can operate through the gloves connected to the cabinet, commonly known as the glove box (Golve box). The transfer box of the door enters and exits the safety cabinet to ensure that it is not contaminated, and is suitable for high-risk biological tests, such as SARS and Ebola virus related experiments.
Filters are an important part of the ventilation devices of clean equipment such as biological safety cabinets, ultra-clean workbenches, and fume hoods. ULPA ultra high efficiency filter and HEPA high efficiency filter, these two air filters are specially designed to remove most of the extremely small particle pollutants in the airflow. The two filters may be similar in function, but the performance of the two is quite different. The main difference between the two is that the retention efficiency is different. HEPA filters 0.3μm particles, smoke and microorganisms. The efficiency is more than 99.97%; ULPA's filtration efficiency for 0.1-0.2μm particles, smoke and microorganisms and other dust particles is more than 99.999%, and for 0.3μm particles, it is more than 99.9999%.