All types of biosafety cabinets in Shanghai Xinzhuang use filters in the exhaust and air intakes. The first-class biosafety cabinet itself has no fan, and relies on the fan in the external air duct to drive the airflow. Since it cannot provide protection for the test articles or products, it has been used less frequently.
The secondary biosafety cabinet is currently the most widely used cabinet type. Like Class I biosafety cabinets, Class II biosafety cabinets also have airflow into the front window opening, known as the "inlet airflow", to prevent aerosols that may be generated during microbial operations from escaping from the front window. Unlike Class I biosafety cabinets, the unfiltered intake air stream is captured by the incoming grid before reaching the work area, so the test product is not contaminated by outside air. A unique feature of the Class II biosafety cabinet is that the vertical laminar airflow filtered through the HEPA filter is blown from the top of the safety cabinet and is referred to as the "downward flow." The sinking airflow is continuously blown through the working area of ​​the safety cabinet to protect the test items in the cabinet from external dust or bacteria.
According to the regulations, the secondary biosafety cabinet can be divided into four levels according to the inlet airflow speed, exhaust mode and circulation mode: A1 type, A2 type, B1 type and B2 type. All secondary biosafety cabinets provide protection for workers, the environment and products.
For the test bench, the minimum airflow velocity or the average value of the front window of the A1 safety cabinet of the fume hood should be at least 0.38m/s. 70% of the gas is recirculated through the HEPA filter to the work area and 30% of the gas is filtered through the vent. The minimum airflow velocity or average of the front window of the A2 safety cabinet should be at least 0.5m/s. 70% of the gas is recirculated through the HEPA filter to the work area and 30% of the gas is filtered through the vent. The negative pressure of the A2 safety cabinet surrounds the contaminated area and prevents the leakage of substances in the cabinet.
The Class B B biosafety cabinets are safety cabinets connected to the exhaust system. The fan connected to the exhaust duct of the safety cabinet is connected to the emergency supply power source, and the purpose is to maintain the negative pressure of the safety cabinet under the power failure to prevent dangerous gas leakage such as laboratory. The minimum airflow velocity or average of the front window should be at least 0.5m/s (100fpm). The B1 type 70% gas is removed through the vent HEPA filter and 30% of the gas is recirculated through the supply port HEPA filter to the work area. The B2 is a 100% full-row safety cabinet with no internal circulation airflow and provides both biochemical and chemical safety controls.
The performance of each cabinet type of the second-level biosafety cabinet is designed for the level 4 biosafety level of the third-class biosafety cabinet. It is the safest cabinet with the highest safety protection level in the world. The cabinet is completely airtight, 100% fully exhausted, all gases are not involved in the cycle, the staff is operated by gloves connected to the cabinet, commonly known as glove boxes, and the test products enter and exit the safety cabinet through the double-door transfer box to ensure no pollution. Suitable for high-risk biological tests.
An A2 type secondary biosafety cabinet with an external drain pipe cover can be used under operating conditions that allow for the circulation of chemical gases. The discharge pipe cover is different from the general hard pipe in that it has an intake hole for sucking air; the discharge pipe cover is connected to the outer pipe and then connected to an external fan. The air intake on the drain pipe cover is essential for the A2 type II biosafety cabinet to maintain the balance of intake and sink airflow through the built-in fan. If a sealed external duct is used, the intake air flow will be too strong, which may cause the safety cabinet to protect the product; and the air inlet hole in the discharge duct cover can draw air from the room without affecting the airflow balance in the safety cabinet. This condition applies only to trace amounts of toxic chemicals. All types of biosafety cabinets use filters on the exhaust and air intakes. The first-class biosafety cabinet itself has no fan, and relies on the fan in the external air duct to drive the airflow. Since it cannot provide protection for the test articles or products, it has been used less frequently.
The secondary biosafety cabinet is currently the most widely used cabinet type. Like Class I biosafety cabinets, Class II biosafety cabinets also have airflow into the front window opening, known as the "inlet airflow", to prevent aerosols that may be generated during microbial operations from escaping from the front window. Unlike Class I biosafety cabinets, the unfiltered intake air stream is captured by the incoming grid before reaching the work area, so the test product is not contaminated by outside air. A unique feature of the Class II biosafety cabinet is that the vertical laminar airflow filtered through the HEPA filter is blown from the top of the safety cabinet and is referred to as the "downward flow." The sinking airflow is continuously blown through the working area of ​​the safety cabinet to protect the test items in the cabinet from external dust or bacteria.
According to the regulations, the secondary biosafety cabinet can be divided into four levels according to the inlet airflow speed, exhaust mode and circulation mode: A1 type, A2 type, B1 type and B2 type. All secondary biosafety cabinets provide protection for workers, the environment and products.
For the test bench, the minimum airflow velocity or the average value of the front window of the A1 safety cabinet of the fume hood should be at least 0.38m/s. 70% of the gas is recirculated through the HEPA filter to the work area and 30% of the gas is filtered through the vent. The minimum airflow velocity or average of the front window of the A2 safety cabinet should be at least 0.5m/s. 70% of the gas is recirculated through the HEPA filter to the work area and 30% of the gas is filtered through the vent. The negative pressure of the A2 safety cabinet surrounds the contaminated area and prevents the leakage of substances in the cabinet.
The Class B B biosafety cabinets are safety cabinets connected to the exhaust system. The fan connected to the exhaust duct of the safety cabinet is connected to the emergency supply power source, and the purpose is to maintain the negative pressure of the safety cabinet under the power failure to prevent dangerous gas leakage such as laboratory. The minimum airflow velocity or average of the front window should be at least 0.5m/s (100fpm). The B1 type 70% gas is removed through the vent HEPA filter and 30% of the gas is recirculated through the supply port HEPA filter to the work area. The B2 is a 100% full-row safety cabinet with no internal circulation airflow and provides both biochemical and chemical safety controls.
The performance of each cabinet type of the second-level biosafety cabinet is designed for the level 4 biosafety level of the third-class biosafety cabinet. It is the safest cabinet with the highest safety protection level in the world. The cabinet is completely airtight, 100% fully exhausted, all gases are not involved in the cycle, the staff is operated by gloves connected to the cabinet, commonly known as glove boxes, and the test products enter and exit the safety cabinet through the double-door transfer box to ensure no pollution. Suitable for high-risk biological tests.
An A2 type secondary biosafety cabinet with an external drain pipe cover can be used under operating conditions that allow for the circulation of chemical gases. The discharge pipe cover is different from the general hard pipe in that it has an intake hole for sucking air; the discharge pipe cover is connected to the outer pipe and then connected to an external fan. The air intake on the drain pipe cover is essential for the A2 type II biosafety cabinet to maintain the balance of intake and sink airflow through the built-in fan. If a sealed external duct is used, the intake air flow will be too strong, which may cause the safety cabinet to protect the product; and the air inlet hole in the discharge duct cover can draw air from the room without affecting the airflow balance in the safety cabinet. This condition applies only to trace amounts of toxic chemicals.
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