Air Distribution Structure and Product Safety
● As a working platform, the blind zone of downdraft around the inner wall of the operating cabin poses a potential product contamination risk. In theory, after the downdraft is filtered by a HEPA filter with an accuracy of 0.3 μm, the air purification quality in the operating platform of the biosafety cabinet can meet the requirements of sterility under empty conditions. However, due to the downdraft blind zone formed around the side wall of the platform, it provides a physical space for the aerosols to stay. In addition, the thermal radiation effect of lighting further exacerbates this situation, creating physical conditions for aerosols to rise in the blind space.
Under normal circumstances, when the work platform is fully covered by downward airflow, the aerosols formed during operations are captured by the negative pressure system along with the descending airflow. However, the existing purification air quality of the work platform is only level 5@0.5μm, primarily due to the presence of airflow blind spots around it. The 0.5μm threshold particle is a representative particle diameter in the bacterial particle group, and the upper limit of the count value for level 5@0.5μm particle size is 3516.76pc/m3. For biosafety cabinets with air volumes between 1000m3/h and 2500m3/h, the risk of product contamination is particularly significant.
It is worth noting that there is no clear separation between this air blind area and the working space. Therefore, once the aerosol in the blind zone is introduced into the working space by the downdraft, the risk of product contamination will increase significantly.
● In the working platform, we observed a significant decline in air quality near the table space and around the blind area, which constituted a direct pollution hazard to the product. After analysis, this phenomenon is due to the fact that the downdraft of class ii biosafety cabinet adopts the forward and backward return air mode, thus forming a clear division of the forward and backward air flow in the space. At the bottom of the airflow division line, because the downdraft bends to both sides during the flow process, a void area of downdraft is formed near the mesa space, which leads to a large amount of aerosol accumulation in this area. This specific airflow pattern significantly increases the risk of contamination of the product.
● During the design process of the Guard A2 Biosafety Cabinet, in order to ensure that its airflow organizational structure fully meets the standards of biological aseptic applications, we adopted a series of rigorous technical means. Firstly, we achieved the downdraft design with full-area coverage, effectively eliminating the physical conditions of aerosol retention and laying a solid foundation for the construction of an aseptic environment. Secondly, we particularly applied zero leakage technology at the junction of the HEPA filter frame and the cabinet to further guarantee the purity of the air quality of the operating platform. Finally, we introduced the countertop air return design to ensure the vertical correction of the downdraft, so as to effectively eliminate the air void effect near the countertop space. Through this series of carefully planned and implemented measures, the Guard A2 Biosafety Cabinet successfully meets the biological aseptic operation requirements of Level 3 @ 0.3 μm, providing reliable product safety guarantee for aseptic application fields such as the bioindustry.
3A2C Technology
The unique 3A2C technology of the Guard A2 series biosafety cabinet integrates cutting-edge technologies such as automatic identification of power and air volume, static pressure relations, automatic sensing of air flow and static pressure changes, and automatic speed regulation. The technology is designed to effectively address the excessive drop in total air flow in biosafety cabinets when total static pressure increases, and significantly reduce the potential risk to personnel and products due to system airflow fluctuations.
"3A" represents three automatic functions: automatic identification, automatic induction and automatic speed regulation; The "2C" refers to two conservation principles: the total gas flow of the system conservation and the flow velocity vector conservation. The application of this technology has made a major breakthrough in the key technology of the Guard A2 series biosafety cabinet in the primary isolation barrier of the biological laboratory.
When the total flow rate of the system decreases excessively, the key is that the inflow velocity vector decreases by 10%. In this state, the inflow airflow velocity vector may be below the minimum velocity requirement (0.5 m / s), resulting in insufficient inflow airflow vector to combat microbial aerosol escape, thereby increasing the risk of human contamination due to reduced barrier capacity.
After in-depth research, we realized the importance of effectively containing the system's airflow fluctuations, especially in terms of potential threats to personnel safety. In the case of 20% reduction in gas flow, the isolation barrier capacity of the system will be significantly reduced to the level of IIA1, unable to meet the requirements of personnel protection in pathogenic microorganism operations. At this time, the isolation barrier capacity caused by the sudden change of air velocity is seriously insufficient, which will greatly increase the risk of personnel pollution.
It is worth noting that although the potential hazards brought by the fluctuation of air flow volume have emerged, the industry and laboratories have not fully recognized its hazardous nature and failed to take effective prevention and control measures against this risk pattern. Especially for the A2 system, it currently only has the alarm prompt function and still lacks the inherent technical means for risk control.
Through the data analysis, it is found that the risk of airflow fluctuation may have occurred before the alarm. This finding may explain the unexplained contamination of clinical medical examiners during the COVID-19 epidemic. Therefore, the fluctuation of air flow rate has become a key technical problem that restricts the performance of primary isolation barrier in biological laboratory.
Currently, in biosafety cabinet applications, airflow fluctuations are usually only detected after the system alarms. In order to ensure the safety of laboratory personnel, it is urgent to conduct in-depth research and development of the "constant wind speed" technology of the system to effectively deal with safety risks.
The total gas flow rate of the system decreases with the increase of static pressure, which is a natural phenomenon that kinetic energy transforms into static pressure energy, and conforms to Bernoulli's theorem. The 3A core technology of the Guard A2 series biological safety cabinet achieves precise control and stability of system kinetic energy by expanding the static pressure range, ensuring that the system's airflow velocity vector change approaches zero within the static pressure design range, thereby optimizing system performance and improving stability