The Xiaomi Smart Air Purifier 4 Compact Filter Offers You A High-Quality Three-Layer High-Efficiency Filtration System To Protect Your Health. The All-In-One Powerful Filter Gives You Layers Of Purification For A Much Cleaner Air Output. This Filtration System Consists Of A Primary Filter, Xiaomi’s High-Efficiency Filter And A High-Quality Activated Carbon Filter That Work Together To Purify Your Air And Keep You Healthy