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劲威全体员工 All staff of Jinwei
生物安全柜的工作原理：
生物安全柜的工作原理主要是将柜内空气向外抽吸，使柜内保持负压状态，通过垂直气流来保护工作人员；外界空气经高效空气过滤器( high-efficiency particulate air filter, HEPA过滤器)过滤后进入安全柜内，以避免处理样品被污染；柜内的空气也需经过HEPA过滤器过滤后再排放到大气中，以保护环境。
生物安全柜的结构
生物安全柜一般由箱体和支架两部分组成。箱体部分主要包括以下结构：
1. 空气过滤系统
空气过滤系统是保证本设备性能最主要的系统，它由驱动风机、风道、循环空气过滤器和外排空气过滤器组成。其最主要的功能是不断地使洁净空气进入工作室，使工作区的下沉气流(垂直气流)流速不小于0.3m/s，保证工作区内的洁净度达到100级。同时使外排气流也被净化，防止污染环境。
该系统的核心部件为HEPA过滤器，其采用特殊防火材料为框架，框内用波纹状的铝片分隔成栅状，里面填充乳化玻璃纤维亚微粒，其过滤效率可达到99.99%~100%。进风口的预过滤罩或预过滤器，使空气预过滤净化后再进入HEPA过滤器中，可延长HEPA过滤器的使用寿命。
2. 外排风箱系统
外排风箱系统由外排风箱壳体、风机和排风管道组成。外排风机提供排气的动力，将工作室内不洁净的空气抽出，并由外排过滤器净化而起到保护样品和柜内实验物品的作用，由于外排作用，工作室内为负压，防止工作区空气外逸，起到保护操作者的目的。
3. 滑动前窗驱动系统
滑动前窗驱动系统由前玻璃门、门电机、牵引机构、传动轴和限位开关等组成，主要作用是驱动或牵引各个门轴，使设备在运行过程中，前玻璃门处于正常位置。
4. 照明光源和紫外光源位于玻璃门内侧以保证工作室内有一定的亮度和用于工作室内的台面及空气的消毒。
5.控制面板上有电源、紫外灯、照明灯、风机开关、控制前玻璃门移动等装置，主要作用是设定及显示系统状态。
生物安全柜的分级
按照NSF49标准，生物安全等级1级(P1)的媒质是指普通无害细菌、病毒等微生物；生物安全等级2级(P2)的媒质是指一般性可致病细菌、病毒等微生物；生物安全等级3级(P3)的媒质是指烈性/致命细菌、病毒等微生物，但感染后可治愈；生物安全等级4级(P4)的媒质是指烈性/致命细菌、病毒等微生物，感染后不易治愈。此标准将生物安全柜分为Ⅰ、Ⅱ、Ⅲ级，可适用于不同生物安全等级媒质的操作。
生物安全实验室选用生物安全柜的原则
当实验室级别为一级时一般无须使用生物安全柜，或使用Ⅰ级生物安全柜。实验室级别为二级时，当可能产生微生物气溶胶或出现溅出的操作时，可使用Ⅰ级生物安全柜；当处理感染性材料时，应使用部分或全部排风的Ⅱ级生物安全柜；若涉及处理化学致癌剂、放射性物质和挥发性溶媒，则只能使用Ⅱ-B级全排风(B2型)生物安全柜。实验室级别为三级时，应使用Ⅱ级或Ⅲ级生物安全柜；所有涉及感染材料的操作，应使用全排风型Ⅱ-B级(B2型)或Ⅲ级生物安全柜。实验室级别为四级时，应使用Ⅲ级全排风生物安全柜。当人员穿着正压防护服时，可使用Ⅱ-B级生物安全柜。
生物安全柜的安装
1. 生物安全柜在运输过程中不得侧置、冲击、碰撞，且不能受雨雪的直接侵袭及日光暴晒。
2. 生物安全柜的工作环境为10~30℃ ,相对湿度为<75%。
3. 设备应安装在不能移动的水平面上。
4. 设备必须安装在靠近固定电源插座处，在没有连接外排系统的情况下，其顶部距离房间顶部障碍物至少200mm距离，后面与墙面间隔至少300mm距离，以利于外排气流畅通和安全柜的维护。
5. 为了防止气流干扰，要求不得将设备安装在人员往来的通道中，并且不得使生物安全柜滑动前窗操作口正对实验室的门窗或靠门窗太近，应远离人员活动，物品流动及可能会扰乱气流的地方。
6. 在高海拔地区使用，安装后必须重新校正风速。
生物安全柜的使用
1. 接通电源。
2. 穿好洁净的实验工作服，清洁双手，用70%的酒精或其他消毒剂全面擦拭安全柜内的工作平台。
3. 将实验物品按要求摆放到安全柜内。
4. 关闭玻璃门，打开电源开关，必要时应开启紫外灯对实验物品表面进行消毒。
5. 消毒完毕后，设置到安全柜工作状态，打开玻璃门，使机器正常运转。
6. 设备完成自净过程并运行稳定后即可使用。
7. 完成工作，取出废弃物后，用70%的酒精擦拭柜内工作平台。维持气流循环一段时间，以便将工作区污染物质排出。
8. 关闭玻璃门，关闭日光灯，打开紫外灯进行柜内消毒。
9. 消毒完毕后，关闭电源。
注意事项：
1. 为了避免物品间的交叉污染，整个工作过程中所需要的物品应在工作开始前一字排开放置在安全柜中，以便在工作完成前没有任何物品需要经过空气流隔层拿出或放入，特别注意：前排和后排的回风格栅上不能放置物品，以防止堵塞回风格栅，影响气流循环。
2. 在开始工作前及完成工作后，需维持气流循环一段时间，完成安全柜的自净过程，每次试验结束应对柜内进行清洁和消毒。
3. 操作过程中，尽量减少双臂进出次数，双臂进出安全柜时动作应该缓慢，避免影响正常的气流平衡。
4. 柜内物品移动应按低污染向高污染移动原则，柜内实验操作应按从清洁区到污染区的方向进行。操作前可用消毒剂浸湿的毛巾垫底，以便吸收可能溅出的液滴。
5. 尽量避免将离心机、振荡器等仪器安置在安全柜内，以免仪器震动时滤膜上的颗粒物质抖落，导致柜内洁净度下降；同时这些仪器散热排风口气流可能影响柜内的气流平衡。
6. 安全柜内不能使用明火，防止燃烧过程中产生的高温细小颗粒杂质带入滤膜而损伤滤膜。
生物安全柜的维护
为了保障生物安全柜的安全性，应定期对安全柜进行维护和保养：
1. 每次使用前后应对安全柜工作区进行清洁和消毒。
2. HEPA过滤器的使用寿命到期后，应由接受过生物安全柜专门培训的专业人员更换。
3. WHO颁布的实验室生物安全手册、美国生物安全柜标准NSF49和中国食品药品监督管理局生物安全柜标准YY0569都要求有下列情况之一者，应对生物安全柜进行安全检测：安装完毕投入使用前；一年一度的常规检测；当安全柜移位后；更换HEPA过滤器和内部部件维修后。
安全检测包括以下几个方面：
1. 进气流流向和风速检测：进气流流向采用发烟法或丝线法在工作断面检测，检测位置包括工作窗口的四周边缘和中间区域；进气流风速采用风速计测量工作窗口断面风速。
2. 下沉气流风速和均匀度检测：采用风速仪均匀布点测量截面风速。
3. 工作区洁净度检测：采用尘埃粒子计时器在工作区检测。
4. 噪声检测：生物安全柜前面板水平中心向外300mm，且高于工作台面380mm处用声级测量噪声。
5. 光照度检测：沿工作台面长度方向中心线每隔30cm设置一个测量点。
6. 箱体漏泄检测：给安全柜密封并增压到500Pa，30分钟后在测试区连接压力计或压力传感器系统用压力衰减法进行检测，或用肥皂泡法检测 。
Working principle of biosafety cabinet:
The working principle of biosafety cabinet is to draw air out of the cabinet, keep the negative pressure state in the cabinet, and protect the staff by vertical air flow; The external air is filtered by high efficiency special air filter (HEPA filter) and then enters the safety cabinet to avoid the pollution of the treated samples; The air in the cabinet also needs to be filtered by HEPA filter before being discharged into the atmosphere to protect the environment.
Structure of biosafety cabinet
Biosafety cabinet is generally composed of box and support. The box part mainly includes the following structures:
1. air filtration system
Air filtration system is the most important system to ensure the performance of the equipment, which consists of driving fan, air duct, circulating air filter and external air filter. The main function of the system is to keep clean air into the workshop, and make the flow rate of downdraft (vertical air flow) in the work area not less than 0.3m/s, so as to ensure the cleanliness of the working area reaches 100. At the same time, the external exhaust flow is also purified to prevent pollution of the environment.
The core part of the system is HEPA filter, which adopts special fire-proof material as frame, and the corrugated aluminum sheet is used to separate it into grid shape. The filter efficiency can reach 99.99% - 100% with the emulsion glass fiber sub particles. The pre filter cover or pre filter of air inlet can make the air pre filter clean before entering HEPA filter, which can prolong the service life of HEPA filter.
2. external exhaust air box system
The outer exhaust air box system consists of the outer exhaust box shell, fan and exhaust duct. The exhaust fan provides the power to exhaust, draws out the unclean air in the workshop, and purifies it by the external filter to protect the sample and the experimental articles in the cabinet. Due to the external discharge, the working room is negative pressure to prevent the air escaping from the working area, and plays the purpose of protecting the operator.
3. sliding front window drive system
Sliding front window drive system consists of front glass door, door motor, traction mechanism, transmission shaft and limit switch, etc. the main function is to drive or pull each door shaft, so that the front glass door is in normal position during the operation of the equipment.
4. the lighting source and ultraviolet light source are located inside the glass door to ensure certain brightness in the studio and disinfect the worktable and air in the studio.
5. the control panel is equipped with power supply, UV lamp, lighting lamp, fan switch, front glass door movement and other devices, which mainly functions as setting and displaying system status.
Classification of biosafety cabinets
According to nsf49 standard, medium with biosafety level 1 (P1) refers to ordinary harmless bacteria, viruses and other microorganisms; Medium with Biosafety Level 2 (P2) refers to the general pathogenic bacteria, viruses and other microorganisms; The medium of level 3 (P3) of biosafety is a strong / lethal bacteria, virus and other microorganisms, but it can be cured after infection; The medium of biosafety grade 4 (P4) refers to the strong / lethal bacteria, viruses and other microorganisms, which are not easy to cure after infection. The biosafety cabinet is divided into grade I, Ⅱ and III, which can be used for the operation of medium of different biosafety levels.
Principles of biosafety laboratory selection of biosafety cabinet
When the laboratory level is level I, it is not necessary to use biosafety cabinet or class I biosafety cabinet. When the laboratory level is level 2, the class I biosafety cabinet can be used when microbial aerosol or splashing operation is possible; When dealing with infectious materials, the class II biosafety cabinet with partial or all exhaust air shall be used; If it involves the treatment of chemical carcinogens, radioactive substances and volatile solvents, only class II-B full exhaust air (type B2) biosafety cabinet can be used. When the laboratory level is level 3, the class II or class III biosafety cabinet shall be used; All operations involving infected materials shall be equipped with full exhaust type II-B (type B2) or class III biosafety cabinet. When the laboratory level is level 4, class III full exhaust biosafety cabinet shall be used. When the personnel wear positive pressure protective clothing, class II-B biosafety cabinet can be used.
Installation of biosafety cabinet
1. the biosafety cabinet shall not be placed, impacted or collided in the transportation process, and shall not be directly affected by rain and snow and exposed to sunlight.
2. the working environment of biosafety cabinet is 10-30 ℃, and the relative humidity is less than 75%.
3. the equipment shall be installed on the level which cannot be moved.
4. the equipment must be installed near the fixed power socket. Without connecting the external drainage system, the top of the equipment must be at least 200mm away from the obstacles at the top of the room and at least 300mm from the wall at the back to facilitate the smooth flow of the exhaust air and the maintenance of the safety cabinet.
5. in order to prevent air flow interference, it is required that the equipment shall not be installed in the passage of personnel communication, and the operating port of the front window of biosafety cabinet shall not be located too close to the door and window of the laboratory, and it shall be away from personnel activities, articles flow and places that may disturb the air flow.
6. when used in high altitude areas, the wind speed must be corrected again after installation.
Use of biosafety cabinet
1. turn on the power.
2. wear clean experimental work clothes, clean hands, and wipe the working platform in the safety cabinet with 70% alcohol or other disinfectant.
3. put the experimental items in the safety cabinet as required.
4. close the glass door and open the power switch. If necessary, the UV lamp shall be turned on to sterilize the surface of the test article.
5. after disinfection, set to the working state of safety cabinet, open the glass door, and make the machine operate normally.
6. the equipment can be used after the self purification process is completed and the operation is stable.
7. finish the work, after taking out the waste, wipe the working platform inside the cabinet with 70% alcohol. Maintain the air flow circulation for a period of time in order to discharge the pollutants from the work area.
8. close the glass door, close the fluorescent lamp, turn on the UV lamp for disinfection in the cabinet.
9. after disinfection, turn off the power supply.
matters needing attention:
1. in order to avoid cross contamination between articles, the items needed in the whole work process shall be arranged in the safety cabinet one word before the work starts, so that no items need to be taken out or put into the air flow partition before the completion of the work. Special attention: the return air grill in the front and rear cannot be placed on the air return grid to prevent blocking the air return grid and affecting the air circulation.
2. before and after the work, the air flow cycle shall be maintained for a period of time to complete the self purification process of the safety cabinet. The cabinet shall be cleaned and sterilized at the end of each test.
3. during operation, the number of arms in and out shall be minimized. When the two arms enter and exit the safety cabinet, the action shall be slow to avoid affecting the normal air flow balance.
4. the moving of the objects in the cabinet shall be in accordance with the principle of low pollution to high pollution, and the laboratory operation in the cabinet shall be conducted in the direction from clean area to pollution area. Before operation, use disinfectant soaked towel to cushion the bottom to absorb the droplets that may splash.
5. try to avoid placing centrifuges, oscillators and other instruments in the safety cabinet to avoid the particles on the filter film shake off when the instrument vibrates, resulting in the decrease of the cleanliness in the cabinet; At the same time, the air flow of the cooling and exhaust air of these instruments may affect the air balance in the cabinet.
6. open fire cannot be used in the safety cabinet to prevent the high temperature and fine particles impurities generated during combustion from being brought into the filter membrane and damage the filter membrane.
Maintenance of biosafety cabinet
In order to ensure the safety of biosafety cabinet, the safety cabinet shall be maintained and maintained regularly:
1. before and after each use, the working area of the safety cabinet shall be cleaned and sterilized.
2. after the service life of HEPA filter expires, it shall be replaced by professional trained by biosafety cabinet.
3. the laboratory biosafety manual issued by who, the American biosafety cabinet standard nsf49 and the biosafety cabinet standard of China food and Drug Administration yy0569 all require that the biosafety cabinet be tested for safety if any of the following conditions are required: before installation is completed and put into use; Annual routine testing; When the safety cabinet is displaced; After replacing HEPA filter and internal components for repair.
Safety inspection includes the following aspects:
1. air flow direction and wind speed detection: the inlet flow direction is detected in the working section by the method of smoke or silk line, and the detection position includes the surrounding edge and middle area of the working window; The wind speed of intake flow is measured by anemometer in the section of the working window.
2. detection of wind speed and uniformity of downdraft: adopt anemometer to evenly distribute points to measure the cross-section wind speed.
3. cleanliness detection of working area: dust particle timer is used to detect in the working area.
4. noise detection: the horizontal center of the front panel of biosafety cabinet is 300mm outward, and the noise is measured with sound level at 380mm higher than the working table.
5. illuminance detection: set a measuring point every 30cm along the center line of the length of the worktable.
6. leakage detection of the box: seal and pressurize the safety cabinet to 500pa. After 30 minutes, connect the pressure gauge or pressure sensor system in the test area to detect by pressure attenuation method or by soap bubble method.
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