The Mi Air Purifier Filter (Antibacterial) is coated with an antibacterial layer which can quickly and effectively kills the bacteria and dust mites. The primary filter can intercept large particles. The filter easily absorbs methanal and PM 2.5 particles in the air. It has a quadruple purification effect and excellently purifies the air. The filter can be used for up to a year. The Mi App will remind you when the filter needs replacing.