Answer A Few Questions About Biological Safety Cabinets

Answer A Few Questions About Biological Safety Cabinets

Biological safety cabinets can be divided into three categories: first-class, second-class and third-class to meet different biological research and epidemic prevention requirements. It is a common and important equipment in biosafety laboratories, which is different from fume hoods or laminar flow hoods in chemical laboratories. For the selection and use of equipment, users will inevitably encounter various problems. In response to customer feedback and inquiries, the biometer editor will answer several questions about biological safety cabinets:

内页11. How to distinguish different levels of 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.

Biological safety cabinets can be divided into Class I, Class II, and Class III.

Class I biological safety cabinets protect workers and the environment without protecting samples.

The airflow principle is the same as that of a laboratory fume hood, except that the exhaust port is fitted with a HEPA filter. The first-class biological safety cabinet itself has no fan.

Class II biological safety cabinets are the most widely used cabinets at present.

Like Class I biological safety cabinets, Class II biological safety cabinets also have airflow into the front window opening, called “air intake”, to prevent the escape of aerosols that may be generated during microbial manipulation through the front window. Unlike Class I biological safety cabinets, the unfiltered intake air will be captured by the intake grille before reaching the work area, so the test item will not be polluted by the outside air. A unique feature of Class II biological safety cabinets is that the vertical laminar airflow filtered by the HEPA filter is blown down from the top of the cabinet, called “downdraft”. The downdraft air continuously blows through the working area of ​​the safety cabinet to protect the test items in the cabinet from contamination by external dust or bacteria. Therefore, all Class II biological safety cabinets provide protection for workers, the environment, and products.

The Class III biological safety cabinet is designed for the Class 4 laboratory biological safety level and is the safety cabinet with the highest safety protection level currently available.

The cabinet is completely airtight and fully exhausted. All gases do not participate in the circulation. The staff operates through the gloves connected to the cabinet, commonly known as the glove box (Golve box). Contaminated, suitable for high-risk biological experiments.

2. What are the classification and selection of Class II biological safety cabinets?

Class II biological safety cabinets are divided into four types: A1, A2, B1, and B2 according to the proportion of the exhaust airflow to the total system flow and the internal design structure.

The minimum amount or average measured value of the airflow velocity at the front window of the A1 type safety cabinet shall be at least 0.4m/s. 70% of the gas in the safety cabinet is filtered by the air filter and then circulated to the work area, and 30% of the gas is discharged through the air filter at the exhaust port. The polluted air in the safety cabinet can be discharged to the laboratory after being filtered by the air filter or discharged to the atmosphere through the exhaust duct through the external exhaust interface of the safety cabinet.

The minimum amount or average measured value of the airflow velocity at the front window of the A2 type safety cabinet shall be at least 0.5m/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 polluted air in the safety cabinet can be discharged to the laboratory after being filtered by the air filter or discharged to the atmosphere through the exhaust duct through the external exhaust interface of the safety cabinet. The negative pressure of the safety cabinet is designed to surround the polluted area, preventing the leakage of substances in the cabinet.

The minimum flow rate of the air flowing into the operation port of the front window of the B1 type biological safety cabinet is 0.50m/s, 30% of the gas in the cabinet is filtered through the air filter and then recycled, and 70% of the gas is filtered through the exhaust port HEPA filter and then passed through A dedicated air duct discharges into the atmosphere. All biologically contaminated parts should be kept under negative pressure, or surrounded by negative pressure channels and negative pressure ventilation systems.

The minimum flow rate of the air flowing into the operation port of the front window of the B2 type biological safety cabinet is 0.5m/s. The air in the cabinet is filtered and discharged into the atmosphere, and it is not allowed to enter the safety cabinet for circulation or return to the laboratory, which can provide biological and chemical safety control at the same time. All contaminated parts should be in a negative pressure state or surrounded by a negative pressure area.

内页23. What are the main indicators of biological safety cabinet testing?

Biological safety cabinet testing mainly includes physical testing and biological testing, which can be divided into secondary testing and subsequent testing according to the nature of testing. In addition to the annual routine inspection of biosafety cabinets, on-site biosafety cabinet inspections must also be performed in one of the following situations, such as after installation, after moving, after maintenance, and after changing filters.

4. What are the precautions for using biological safety cabinets?

1. Pay attention to the self-cleaning cycle of the safety cabinet. When opening and closing the safety cabinet, let the safety cabinet run a self-cleaning cycle of 3-5 minutes. This self-cleaning procedure removes airborne contaminants that may be present in the work area of ​​the cabinet.

2. Ensure that the front window of the safety cabinet is at the correct rated operating height when the safety cabinet is working.

3. Ultra-clean workbench ≠ biological safety cabinet. The clean bench looks very similar to the biological safety cabinet, but the clean bench only protects the samples in the work area from the external environment, and does not protect the operator.

4. Do not use biological safety cabinets to handle toxic, flammable, explosive and other materials.

5. The use of open flames should be avoided. The thermal effect of the open flame will interfere with the stability of the airflow in the operating area of ​​the biological safety cabinet, and the heat of the flame will affect the life of the filter. If it must be used, ready-to-use sterilizers or micro-contact burners can be selected as required.

6. Dress correctly to provide the necessary protection during operation. When performing high-risk operations, such as biosafety level 2+ to 3 operations, use a long, open-back gown and two pairs of gloves, and ensure that the outer glove covers the opening of the gown. No exposed skin.

7. Operate in a safe area. Never block the ventilation grills in the front and rear of the work area. Try to work in the center of the work area.

8. Follow the operation principle from clean area to polluted area. The work area of ​​the biological safety cabinet should be divided into three areas in turn: the clean area, the work area and the contaminated area. Biohazardous waste bags should be placed in the contaminated area; experimental instruments and samples should be placed in the work area; and experimental supplies should be placed in the clean area. Experimental operations on the work surface should be carried out in the direction from the clean area to the contaminated area.

9. Do not place too many items in the biological safety cabinet, otherwise it will affect the airflow and safety performance of the safety cabinet.

10. Reasonably choose the installation location of the biological safety cabinet. External airflow disturbances such as doors and windows, air conditioning vents, personnel aisles, and other laboratory airflow disturbance devices (safety cabinets, fume hoods, etc.) should be kept as far away as possible.

11. UV lamps are generally not required in biological safety cabinets. If UV lamps are used, they should be cleaned weekly to remove dust and dirt that may interfere with their germicidal effectiveness.

12. Before and after the use of the safety cabinet, please follow the procedures to sterilize the surface of the safety cabinet. Use an appropriate disinfectant, such as a 70% isopropyl alcohol solvent, to wipe down the work area surfaces of the safety cabinet, including the near-term grills front and rear.

5. How to judge that the filter needs to be changed?

内页31. When the airflow pattern is changed. Through testing, it is found that the vertical airflow (downward airflow) has dead ends and backflow, and there is smoke leaking out of the cabinet, or when the smoke entering the cabinet escapes.

2. If the accumulative running time of the fan on the control panel reaches 10,000 hours, it is usually necessary to replace the filter, but it is not necessary, and the cleanliness of the use environment and usage habits should also be considered.

3. The wind speed becomes smaller. When it is found that the cleanliness index is normal, the flow rate of the descending airflow or the inflow airflow becomes small; or during the operation of the equipment, if the equipment emits an audible and visual alarm and it is caused by the low flow rate of the descending airflow or the inflow airflow (the displayed value in the display window is low, respectively). According to the design requirements), it means that the filter is clogged very seriously, the fan speed has reached the maximum value, and the system cannot reach the specified wind speed value no matter how it is adjusted, and the filter must be replaced at this time.

4. The pressure sensor alarms. When the pressure indicator shows a value greater than 170Pa, the alarm system will alarm.

5. Check the integrity of the filter and find a leak.

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Established in 2011, Biometer Co., Ltd. has been focusing on one-stop-shop solutions for research, development and marketing of medical equipment and laboratory equipment products for various fields covering government departments, scientific research institutions, colleges, biomedicine, advanced material, chemical industry, environment, food, electronics and electrical appliances, etc. for more than 10 years. Our products include laboratory equipment, sterilizer and disinfection equipment, laboratory safety protection product, cold chain product, medical equipment, general analytical equipment, measuring equipment, physical test equipment etc. We also provide sterilizers and autoclaves of different models to meet the diversified requirements of customers.

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  • Post time: Jun-22-2022