Our Windmill Air Purifier 3-in-1 Filter features a Medical-Grade HEPA (H13) Filter, an Activated Carbon Filter, and a Pre-Filter that helps protect your air from 99.97% of small airborne pollutants (including some particles as small as 0.1 microns). The filter typically lasts about 6 months and needs to be replaced to be effective. This is compatible with The Air Purifier (not The Air Purifier Max).