1) PP filter to collect big dust particles and to prolong the lifetime of HEPA;
2) HEPA to filter the floating particles and pollen with small wind resistance;
3) Cold catalyst filter to decompose the harmful gasses in the air;
be effective under the ambient temperpature, requiring no illumination.
4) Activated carbon filter to eliminate unpleasant odors.
5) Built-in ionizer to release negative ions (3.86x106 ions/m3 concentrated)