The filter will collect up to 99.97% particles as small as 0.3 um in size such as carbon dust, bacteria, legionella, combustion smoke, milled flour, welding fumes, pollen, bacteria, pet dander and mold spores. With normal usage, it is recommended that you change this filter every 12 months to keep your ventilation system running smoothly while ensuring you get the fresh indoor air you deserve. The set includes one replacement HEPA filter.