Anti-formaldehyde = The Xiaomi air purifier filter can effectively absorb PM2.5 particles, dust mites. Covered with the special antibacterial layer, it can kill the bacteria. The activated carbon can eliminate the pollutants and odours in the air. Is a filter that filters more than the S1.

S1= Captures up to 99% of dust, pollen, dander, mould spores etc. less. So it is a standard filter without chichi.