Difference between Type A and Type B of standard biosafety cabinets

The experimental platform in the Xinzhuang Instrument Biological Safety Cabinet of Shanghai, 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.
If circulating chemical gases are not permitted, a B2 type secondary biosafety cabinet equipped with a rigid tube must be used. Since the B-type safety cabinet is not an independent balancing system, its built-in fan can only produce a downdraft flow, and the safety cabinet relies on an external exhaust fan to make the intake air flow. This type of safety cabinet is complicated to install and maintain, because the external exhaust fan must be balanced with the built-in fan, otherwise it will lead to the failure of the safety performance of the operator or product. 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.
If circulating chemical gases are not permitted, a B2 type secondary biosafety cabinet equipped with a rigid tube must be used. Since the B-type safety cabinet is not an independent balancing system, its built-in fan can only produce a downdraft flow, and the safety cabinet relies on an external exhaust fan to make the intake air flow. This type of safety cabinet is complicated to install and maintain, because the external exhaust fan must be balanced with the built-in fan, otherwise it will lead to the failure of the safety performance of the operator or product.

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