home air purifier 1.Pre-filter+HEPA+Active carbon+N-ion 2. ... ,Highly efficient,4-Stage air filtration system: Pre-filter + HEPA + Active carbon + N-ion.Eliminate airborne small ... way in, three-way out.Pre-filter---Collect large dust particles HEPA filter---Purification efficiency is 99.97% ... smoke,food smells,and other malodor.Nano filter---superoxide ions.Utilizing the strong oxidation strength ...