Respro Techno masks have replaceable combination filters. With Dynamic Activated Charcoal Cloth DACC/HEPA style particle filter media, Respro Techno Replacment Mask filters trap smoke, odors, exhaust fumes, perfume, fragrance and common particles like dust, pollen, dirt and mold spores. Filters trap particles less than 1 micron in size and larger. Simply replace these mask filters when breathing becomes difficult or there is a noticeable change in performance. Average filter lifespan is 50-60 hours of use. For extended storage periods, the filter should be removed from the shell and allowed to dry before storing. All used filters should be discarded. Two replacement filters per pack. *Fits all Respro Techno and Sportsa medium masks.