Comprehensive Guide to the Use and Selection of Laboratory Biosafety Cabinets

As a guaranteeThe core equipment of the triple safety of personnel, samples, and environment, the biosafety cabinet is not an upgraded version of an ordinary fume hood. Especially in laboratories with biosafety level two or above, it is a 'safety barrier'. Today, we will comprehensively dismantle the core logic, usage standards, and selection techniques of biosafety cabinets to help you maintain the bottom line of laboratory safety.01Many practitioners tend to fall into the misconception of "the one that can exhaust is the safety cabinet" and even use ordinary fume hoods instead of biological safety cabinets to handle dangerous samples. But the core difference between the two lies in the "direction of protection", and misuse may lead to fatal risks: ordinary fume hoods only guarantee "environmental safety" and exhaust harmful gases through ventilation, which cannot protect operators or avoid sample contamination; Biosafety Cabinet: Achieving triple protection of "personnel, samples, and environment", it can filter pollutants exhaled by operators to prevent sample contamination, and filter aerosols generated during the treatment process before discharge to avoid environmental diffusion.02The "protective password" biosafety cabinet can achieve triple protection, relying on three core technology systems, and every detail is related to security:

01#Efficient airflow control system: building a solid 'invisible protective wall'#This is the "core defense line" of the biosafety cabinet, which blocks the pollution path through precise airflow design: vertical laminar air supply: topHEPAHigh efficiency filter (filtration efficiency ≥99.995%@0.3Mm）Generate uniform vertical laminar flow, forming a "clean protection zone" to avoid sample contamination by pollutants in the environment; Negative pressure surround design: The safety cabinet maintains a negative pressure state inside (different levels of negative pressure have different values, level II)A2The type is usually-10Pa±3Pa）To prevent internal aerosol leakage into the operating area; Airflow circulation filtration: Aerosols generated during the operation process are sucked in through the front suction port, first through a pre filter, and then throughHEPAFilter filtration, clean air can either be recycled or discharged outdoors to avoid polluting the environment.02#Efficient filtration system: making pollutants "nowhere to hide"#The filtration system is the "heart" of the biosafety cabinet, directly determining the protective effect. The core components include two-stage filters: pre filter: intercepts large particles of dust, hair and other impurities, and protects the backendHEPAFilter, extend its service life, it is recommended to3-6Replace once a month;HEPAEfficient filter: core filtering component, for0.3MmThe filtration efficiency of particles is ≥99.995%It can effectively intercept viruses, bacteria, and other microorganisms. Based on the frequency of use, it is recommended to1-2Conduct integrity testing once a year（PAOScan and replace immediately if it fails. It is worth noting that the biosafety cabinet will be equipped with a "filter failure alarm" function, which will immediately sound and light an alarm when the filtration efficiency drops to the threshold to avoid safety hazards.03#Intelligent security monitoring: real-time protection of security boundaries#To avoid risks caused by operational errors, the biosafety cabinet is equipped with multiple intelligent monitoring functions: airflow speed monitoring: real-time monitoring of air supply and exhaust speeds, deviation from set values (usually air supply)0.38m/s±0.02m/s）Immediately report to the police; UV disinfection linkage: The UV lamp can only be turned on when the cabinet door is closed to a safe height to avoid UV leakage and injury to operators; Cabinet door height warning: The opening height of the cabinet door exceeds the safety threshold (usually ≤20cm）At this time, it automatically prompts and reduces the air volume to prevent aerosol leakage.03Press' level 'to select the right one! Biosafety cabinets are mainly divided into Level I and Level II according to their protection level and structure（A1TheA2TheB1TheB2Type III, Class III, and other types are suitable for different scenarios. Choosing the wrong type may lead to safety hazards or resource waste

01Level II Biosafety Cabinet: The "main model" is suitable for operating with biological safety level II and III pathogens, and is also the choice of most laboratoriesA2Type andB2Widely applicable: Level IIA2Type: capable of handling pathogenic bacteria and viruses (such as influenza virus, Escherichia coli),70%Air circulation utilization,30%Exhaust, no need for external exhaust ducts, flexible installation, suitable for conventional microbiology laboratories and pharmaceutical R&D workshops; Level IIB2Type: Fully ventilated design,100%The air flow is filtered and discharged out of the room, which is suitable for processing highly pathogenic and volatile toxic reagents, such as COVID-19, pestis pestis and other samples processed by CDC.02Level I biosafety cabinet: The basic protection "entry-level model" only guarantees "personnel and environmental safety" and cannot protect samples from contamination. It is suitable for handling low-risk pathogens of biosafety levels I and II, such as ordinary bacterial isolation and cultivation, and has gradually been replaced by Level II biosafety cabinets.03Level III Biosafety Cabinet: "Protection" for High Risk Scenarios Sample Processing: After sampling is completed, immediately label the culture medium information (location, time, operator) and cultivate (bacteria) as required37℃/48h, mold28℃/5To avoid pollution caused by prolonged exposure; Even if the biological safety cabinet is selected correctly, improper operation may still lead to safety accidents. Based on practical laboratory cases, the following eight taboos must be avoided:

taboo1When operating, the height of the cabinet door exceeds the safety threshold (usually ≤)20cm）Causing turbulence in airflow and aerosol leakage; taboo2Inserting the ultraviolet lamp into the arm without turning it off can cause ozone irritation to the respiratory tract, and ultraviolet radiation can damage the skin and eyes; taboo3Using open flames (such as alcohol lamps) inside the safety cabinet can disrupt airflow stability and potentially ignite filter materials; taboo4Samples and consumables are placed too densely, blocking the air intake and affecting airflow circulation, resulting in local pollution; taboo5During the operation, quickly swing the arm to disrupt the laminar airflow and introduce external pollutants into the operating area; taboo6Long term failure to replace filters, failure to conduct integrity testing, and continued use even after a decrease in filtration efficiency; taboo7Wipe the inner wall of the safety cabinet with ordinary cleaning agents, which may contaminate the sample with residual chemical substances and corrode the equipment; taboo8After the experiment, no disinfection treatment was carried out, resulting in the growth of residual pathogens and causing cross contamination.

Equipment cleaning: After each use, rinse the sampling tube with purified water to remove residual culture medium, clean the micropores of the collection head with sterile cotton swabs, air dry and store; Long term maintenance: Conduct a comprehensive performance calibration once a year, including flow accuracy, impact efficiency, etc; Put on a dust cover when storing and place in a dry and ventilated environment (humidity)≤60%）Avoid direct sunlight.

Industry reminder: Biosafety cabinets are mandatory calibration equipment and must be certified by qualified institutions before being put into use. They must be calibrated at least once a year thereafter, and core indicators include airflow velocity, negative pressure valueHEPAEquipment that fails the inspection of filter integrity is strictly prohibited from use.