First, the biological safety cabinet
The biosafety cabinet provides both sample and staff protection. The filtered clean air stream is blown from the top of the safety cabinet and passed through the work area and captured before the worker's breathing zone. The airflow will be filtered before it is vented. Normally the filtered air will be discharged back to the laboratory or discharged outside through the exhaust duct.
Biosafety cabinets for each biosafety level
Biosafety cabinets can be divided into three categories: primary, secondary and tertiary to meet different biological research and epidemic prevention requirements. The primary biosafety cabinet protects the worker and the environment without protecting the sample. The airflow principle is the same as for a laboratory fume hood, except that the vent is fitted with a HEPA filter. All types of biosafety cabinets use HEPA filters in the exhaust and air intakes. The first-class biological safety cabinet itself has no fan, and relies on the fan in the external ventilation pipe to drive the airflow. Since it cannot protect the sample in the cabinet , it has been used less frequently.
The secondary biosafety cabinet is currently used in a wide range of cabinet types. According to the NSF49 regulations, the secondary biosafety cabinet can be divided into four different models according to the inlet airflow speed, exhaust mode and circulation mode: A1 type, A2 (formerly B3) type, B1 and B2 type. All secondary biosafety cabinets provide protection for workers, the environment and samples.
The airflow speed of the A1 type safety cabinet front window 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 front airflow speed of the A2 type 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 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 front window airflow velocity zui small amount or measured average value 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 three-level biosafety cabinet is designed for the level 4 laboratory biosafety level. The cabinet is completely airtight. The staff is operated by the gloves connected to the cabinet. It is commonly called the glove box and the test product passes through the double door. The transfer box enters and exits the safety cabinet to ensure it is free from contamination and is suitable for high-risk biological testing.
Performance ratio of each cabinet type of secondary biosafety cabinet
Second, the international certification standards for biological safety cabinets
In May 2000, the European Committee for Standardization (CEN) promulgated the European standard EN12469:2000 for biosafety cabinets, which officially replaced the standards for biosafety cabinets in EU member states such as German DIN 12950, ​​British BS5726 and French NF X-44-201. Become the unified standard for biosafety cabinets in the EU region.
NSF49 has been around since the 1970s and is recognized as the current standard for biosafety cabinets. In 2002, ANSI/NSF49 was officially recognized by the American National Standards Institute (ANSI) and became the unified standard for US biosafety cabinets.
NSF/ANSI49 and EN12469 are the world's most international biosafety cabinet certifications. These two standards have detailed descriptions and requirements for safety cabinet performance classification and safety performance testing. Safety cabinet standards play an important role in regulating the safety cabinet market and protecting researchers.
Third, the introduction of biosafety level
Biosafety level P1
The substances used for the experimental studies are all known, all of which are well known and have proven to be non-microbial substances that do not cause disease. The study was conducted on a public bench by a routine procedure. No special protection measures are required. Operators are only trained in basic laboratory testing procedures and are usually guided by scientific personnel, and the presence of a biosafety cabinet is not required in such an environment.
Biosafety level P2
The substances used in the experimental studies are known to be moderately dangerous and related to certain common diseases in humans. The operator must be trained in the relevant research and guided by a professional scientific researcher. Prepare for pre-treatment of substances that are prone to contamination or that may cause pollution. Some procedures that may involve or produce harmful biological substances should be carried out in a biosafety cabinet. Under these conditions, the secondary biosafety cabinet is used.
Biosafety level P3
The substances to be tested are generally local or foreign substances that may cause illness or life-threatening by respiratory infection. We need to protect all operators in the surrounding environment from exposure to these potentially hazardous materials. It is usually necessary to use a secondary or tertiary biosafety cabinet.
Biosafety level P4
The substances tested in the study are some very dangerous and deadly toxic substances that can be transmitted through the air and are not currently treated with effective vaccines or treatments. Operators must be trained in conducting this very high-risk substance study and should be familiar with the prevention of these high-risk substances in related operations, protective facilities, laboratory design, etc. It must also be guided by researchers who are very experienced in this field of study. The access to the laboratory should be strictly controlled. The laboratory must be built or built separately in a separate room in a building that is separate from anywhere else, and a detailed operational manual for the study is required for reference. A tertiary safety cabinet is required in such an experimental study.
Fourth, how to choose a biological safety cabinet:
Q: Do I need to buy a biosafety cabinet or a clean bench?
A: The ultra-clean workbench provides protection for the sample and does not provide protection for the operator and the environment; the biosafety cabinet in a broad sense provides protection for the operator, the environment and the sample. So, from the protection you need, you can get the right choice;
Q: Which type of protection level biosafety cabinet should I buy?
A: Generally speaking, unless you need to do some research on unknown bacteria and viruses and living organisms, you need to use a three-level biological safety cabinet. The secondary biological safety cabinet can basically meet our normal working needs. For experiments that do not contain samples of toxic, radioactive, volatile irritating solvents, the A1/A2 (formerly B3) type biosafety cabinet has already met the requirements for use. For hospital system procurement, because the virus and strain types are complex, and the experimental conditions Large changes, it is recommended to use B2 full-row biosafety cabinet;
Q: How to judge the quality of a biosafety cabinet
A: The biosafety cabinet is mainly used for biohazard protection, so the protection consideration for the operator is the main basis for judging the quality of the product. The core technology of the secondary biosafety cabinet is the filter membrane (including membrane material, membrane retention efficiency, membrane life), and the design of the wind tunnel (including the balance of the front operating surface, the settlement wind speed and the uniformity of the wind speed, the inlet air velocity). , vertical settlement pattern of wind), alarm setting (good biosafety cabinet should include low wind speed alarm, alarm for wrong position of front window, UV interlocking device, B2 full-row model also needs external fan interlock) and negative pressure protection (including side wall negative pressure, back negative pressure, top negative pressure). Therefore, the comparison of the above indicators can be used to know the advantages and disadvantages of the biological safety cabinet;
Q: Why is the balance of the front operating surface an important indicator of a biosafety cabinet?
A: There is an open front operating surface in the secondary biosafety cabinet, which is easy to operate and also brings a possibility of pollution. If the balance is not good, pollution in this area will occur, and normal access to the outside world will not be possible. The operation room pollution sample and the operation of the outdoor leakage pollution operator protection, thus there is a substantial deviation from the design concept of the biological safety cabinet, so the balance problem of the secondary biological safety cabinet in the front operation surface is critical;
Q: Why does the alarm device need a low wind speed alarm?
A: In Europe and the United States, according to the standards of Europe and the United States, each biosafety cabinet is recommended to do a primary technical indicator check. When we buy back the biosafety cabinet and use it for a while, the biosafety cabinet is still in the normal protection of the operator, the environment and the sample. As an operating user, we have no way of knowing it, and once it settles due to the accumulation of the membrane. If the wind speed is reduced, sample contamination may occur. If the wind speed decreases, it may cause people to be contaminated. In the existing national conditions, it is difficult for us to do the annual technical inspection, because there is no small cost, so the low wind speed alarm is very important;
Q: The biosafety cabinet has an electric front window, is it very convenient and very good?
A: Wrong! In Europe and the United States, a biohazard laboratory often needs to be equipped with a dual power supply system to avoid leakage of biohazardous substances in the event of a power system failure. At home, such laboratory configurations are difficult to obtain. Therefore, once the electric front window is powered off during the experiment, it will cause great danger and cause irreparable damage! Moreover, whether it is an electric front window or a manual front window, it is fixed in height during operation, so on the biological safety cabinet, the electric front window is of little significance and dangerous, and it can be said that there is no harm;
Q: What is the meaning of the side wall negative pressure of the biosafety cabinet?
A: The biosafety cabinets are different in Europe and America. The requirements on the side walls are different. The products in the Americas are stainless steel sidewalls, and the negative pressure chamber is required to avoid the leakage of the sidewalls. European products basically use glass sidewalls, no sidewalls. Do negative pressure protection. Since the operating chamber inside the cabinet is positively pressurized, if there is damage to the housing and the presence of a leak, an outward leak will occur. Therefore, the formation of negative pressure protection on the side wall and the back plate can effectively reduce the possibility of leakage;
Q: How to protect the negative pressure protection cavity from contamination and cross-contamination
A: A good design will be further cleaned and disinfected after a period of work. If there is no such design, the operator needs to continue to open the cabinet for a certain period of time to discharge pollutants after the end of the experimental operation. .
Q: What accessories do we need to order?
A: Generally, some electrical equipment is needed in the cabinet, then the splash-proof power socket in the cabinet is needed, and because the domestic use of European instruments is relatively popular, in view of the inconsistency between the grounding of the European power cord and the socket in China, Will generate a certain amount of static electricity on the European instrument, static electricity will affect the vertical settlement of the wind in the biosafety cabinet, there will be a certain adsorption, so if possible, configure a European splash-proof power outlet. Since the pollution inside the cabinet operation room is not very large, the large pollution of the Zui is in the negative pressure protection chamber, so the UV lamp system can be considered to be selected to achieve better sterilization and disinfection functions. Separately designed safety cabinets need to be equipped with brackets;
In addition to understanding the various performance indicators of the safety cabinet, the way to identify the safety performance of the safety cabinet is to know whether the safety cabinet you purchased has obtained the following major international safety cabinet certifications:
EN12469 (European Biosafety Cabinet Uniform Standard)
NSF49 (US Biosafety Cabinet Standard - Level 2 Biosafety Cabinet)
AS2252.2 (Australian Biosafety Cabinet Standard - Secondary Biosafety Cabinet) JIS K3800 (Japan Biosafety Cabinet Standard)
While seeking product certification from the manufacturer, users may be aware of the following:
1. When a manufacturer claims that its own safety cabinet meets an international standard, it may require proof of it - an independent test report signed by a legal certification body;
2. Some standards may not be directly related to the safety performance of safety cabinets. For example, biosafety cabinet manufacturers claim to obtain ISO9001 quality certification, and ISO9001 does not test the safety cabinet performance of the above international safety cabinet standards;
3. Certification must be tested and promulgated by an independent, legal safety cabinet certification body;
Fifth, the main precautions in the operation of biological safety cabinets:
1. Slow moving principle: In order to avoid affecting the normal wind path state, the hand should be moved as gently as possible during operation in the cabinet.
2, the principle of parallel placement: In order to avoid the phenomenon of cross-contamination between items and articles, the items placed in the cabinet should be placed horizontally as far as possible to avoid cross-contamination during the return air. At the same time, avoid blocking the back air return grille and affecting the normal wind path.
3, to avoid the vibration principle: the cabinet should try to avoid the use of vibration instruments (such as centrifuges, vortex oscillators, etc.), because the vibration will make the particulate matter accumulated on the filter film shake off, resulting in reduced cleanliness inside the operating room, while If the balance of the front operating surface fails, it will also cause the safety cabinet to pollute the operator.
4. Principle of movement in different sample cabinets: When two or more items in the cabinet need to be moved, the principle of moving low-pollution items to highly polluting items must be followed to avoid the occurrence of highly polluting items in the interior of the cabinet during the movement. Large area pollution
5, the use of open fire principles: try not to use open flames in the cabinet! Because fine particle impurities generated during open flame use will be carried into the filter area, these high temperature impurities will damage the filter. When it is unavoidable that it is necessary to use it, it is advisable to use a Bunsen burner with a low flame.
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