Made from Filtrete 2200 pleated filters. Limit one per mask kit. Limit 3 per finished masks.These are considered to be disposable as washing is not recommended. That being said, I cannot give a recommended time frame per use of each filter, especially due to the following statement: PLEASE NOTE THAT THIS IS NOT THE INTENDED USE OF AIR FILTERS. I CANNOT ATTEST TO THE EFFECTIVENESS OR SAFETY OF THEIR USE IN THIS MANNER. PELASE DO YOUR RESEARCH AND USE AT YOUR OWN DISCRETION.