In the air purification system of a cleanroom, the pleated high-efficiency filter (HEPA) achieves terminal air purification through the full-process coordination of “pre-treatment + core filtration + airflow control + sealing guarantee”. The specific path is as follows:
First, rely on the “preprocessing protection” of pre-filtering. Terminal purification is not achieved by HEPA alone. Its front end is connected to primary and medium-efficiency filters to form a “three-stage filtration chain” : the primary filter first removes large particles with a diameter of more than 5μm in the air (such as dust and hair), while the medium-efficiency filter intercepts medium particles with a diameter of 1-5μm (such as pollen and fiber debris). This step can prevent large particles from clogging the precision filter paper of the HEPA, reserve core filtration capacity for terminal deep purification, and at the same time extend the service life of the HEPA.
Secondly, the “high-efficiency filter carrier” relying on its own structure. As the core of terminal purification, the structural design of HEPA directly determines the purification effect First, the filter paper is made of glass fiber or synthetic fiber. The fibers interweave to form a filter layer with extremely small pores, which can precisely capture tiny particles larger than 0.3μm (such as suspended dust and microbial spores), with a filtration efficiency of over 99.97%, meeting the requirements of clean rooms for the removal of fine pollutants. Second, metal or paper partitions divide the filter paper into uniform “V-shaped” air flow channels. This not only avoids uneven air flow caused by the stacking of filter paper but also guides the air to pass through the filter paper at a constant speed, ensuring that every inch of the filtration area fully participates in the purification and preventing local air flow from being too fast and causing particles to penetrate.
Furthermore, through the “deep purification synergy” of multiple filtration mechanisms. During the terminal purification process, HEPA works together through multiple physical effects: for particles with diameters larger than the pore size of the filter paper, it directly blocks them through the “interception effect”; For medium and large-sized particles moving with the airflow, they are captured by using the “inertial impact effect” (when the airflow turns, the particles collide with the filter paper due to inertia). For extremely small particles (such as those below 0.1μm), they are adsorbed through the “diffusion effect” (when particles come into contact with the filter paper fibers during Brownian motion). These mechanisms work in synergy to comprehensively remove tiny particles and microorganisms from the air, achieving deep purification of terminal air.
Finally, rely on the “leak-proof guarantee” of the sealing design. Terminal purification must eliminate the risk of “unfiltered air leakage” : At the connection points between HEPA and the supply air ducts, as well as the frames at the entrance of the clean room, elastic sealant or gaskets will be used to closely adhere to prevent air from bypassing the filters through the gaps and directly entering the clean room. In some high-demand scenarios, “integrity tests” (such as aerosol scanning) will also be conducted after installation to detect any leakage points and ensure that the air output by the terminal is 100% HEPA filtered, ultimately meeting the air cleanliness requirements of different grades from Class 1 to Class 100 in cleanrooms.
