Definition
Purification bench usually refers to an air purification equipment that provides a local dust-free and sterile operating environment. Its core function is to form a space within the operating area with a higher cleanliness level relative to the external environment through a specific airflow organization and filtration system to meet the strict cleanliness requirements of experimental samples or operating processes. It is a common form of vertical flow or horizontal flow clean bench, which is widely used in various experiments and production links where particulate or microbial contamination needs to be avoided.
Principle
The basic operating principle of the purification bench is based on aerodynamics and efficient filtration technology. The internal fan of the equipment draws in ambient air, and after pre-filtration by the primary filter, it is pressed into the hydrostatic chamber by the fan and finally filtered through the high-efficiency air filter. Filtered clean air passes through the operating area at a uniform cross-sectional wind speed (e.g. vertically downward or horizontally oriented) to create a stable one-way flow (laminar flow). This airflow is able to carry out the particles generated in the operating area and expel them through exhaust vents or by exchanging with external air, thus maintaining a high level of cleanliness in the operating area. The airflow mode can be mainly divided into two designs: vertical flow and horizontal flow.
Main technical parameters and measurement methods
Key technical parameters to evaluate the performance of a purification bench include cleanliness, airflow velocity, noise, vibration, and filter integrity. The measurement of these parameters requires reference to relevant domestic and foreign standards, such as the Chinese national standard GB/T 16292-2010, the US federal standard FS 209E, or the relevant parts of the ISO 14644 series of standards of the International Organization for Standardization.
Cleanliness is typically measured by multi-point sampling in the operating area by a particle counter and is rated as the number of particles of a specific particle size (e.g., ≥0.5 μm) per volume of air. The airflow velocity is measured and averaged using a calibrated thermal or impeller anemometer on the flow sharing network or operating area section downstream of the HEPC. The noise level should be measured with a sound level meter at a specified distance in front of the device. Vibration measurement should be carried out by placing the vibration tester in a key position on the workbench. The integrity of the HEPA filter can be verified by upstream dust generation (e.g., PAO, DOP, etc.) and downstream scanning for leak detection using an aerosol photometer.
Performance Factors
The performance of a purification bench is affected by a variety of factors. Operator activities, such as frequent entry and exit or rapid movement of the arm, can interfere with one-way airflow, potentially leading to contaminant entrainment. If the equipment or items placed in the workbench are too large or improperly placed, they will form airflow dead angles and affect the cleanliness uniformity. The installation position of the workbench itself is also crucial, and should be avoided near doorways, vents, and other airflow disturbances or dust sources. In addition, the performance of high-efficiency filters gradually deteriorates with the use of time, and regular performance testing and timely replacement are the basis for maintaining their effectiveness. Infrequent cleaning or replacement of the pre-filter can also accelerate the load and loss of the HEPA.
Applications
The application fields of purification workbenches are very wide. In the field of biomedicine, it is commonly used in aseptic operations such as cell culture, microbial inoculation, and vaccine preparation. In the precision electronics industry, it provides a dust-free environment for the assembly and inspection of semiconductor components and integrated circuits. In the field of optics, the cleaning and assembly of precision lenses and laser components also depend on the clean space they provide. In addition, purification benches are also standard in food microbiology testing, pharmaceutical dispensing, and some materials science experiments that are sensitive to particulate contamination.
Key points to consider in selection
When choosing a purification bench, systematic considerations are required. First, the airflow mode should be determined according to the main type of operation: vertical flow provides better operator protection and is suitable for handling hazardous samples; Horizontal flow provides more direct sample protection for routine aseptic operations. Secondly, it is necessary to clarify the cleanliness level required for the process and select equipment equipped with the corresponding level of high-efficiency filter (e.g. H14 level) accordingly. The size of the operating space needs to meet the needs of experimental equipment placement and operation range. The operating noise and vibration levels of the equipment should be within acceptable limits, especially for sensitive experiments. Additionally, consider the energy consumption of the equipment, ease of maintenance (e.g., filter replacement methods), safety features (e.g., UV lamp interlocks, wind speed alarms), and compatibility with the existing laboratory infrastructure. It is recommended to refer to the technical data provided by the manufacturer that meets the relevant standards for a comprehensive comparison.