Filter removes at least 99.427% of airborne particles*.
Filter is removable and also machine washable. It is rated for 2 to 5 day use in normal average pollution environments. The length of use between washes is a personal matter and up to each individual.
*Independent test results reveal that the average efficiency rating of PNH Reusable Fabric Face Masks with a filter is 99.427% for particles ranging in size 0.1 to .03 microns.