High-efficiency particulate filters are exchanged every year for air purifier manufacturers. HEPA network is also called high-efficiency particulate filter (US-level DOE-STD-3025-2007 is a 0.3 micron removal rate of 99.97% for HEPA network). When you apply high-efficiency particulate filter for a few months, you can turn off mechanical extraction. Net, observe whether the outside of the filter can become dirty and discolored. If the filter is full of dust, you can use a vacuum cleaner to remove the gray outside the filter. Since a large amount of harmful substances such as dust accumulate on the outside of the filter, the filter will not be able to achieve the desired effect, and it will also affect the malfunction of the machine. Air purifier manufacturers look forward to every user's emotional choice.