airnex 10pcs pm 2.5 activated charcoal filter mask inserts - 5 layers protection pm2.5 mask filter insert - pm 2.5 filter mask replacement - filtros para mascarillas airnex ✅ <b>duration of filters</b><br> duration time of filters depends on the pollution level and the frequency of usage. <br> generally speaking, to protect yourself from pollution or any airborne contaminant, we recommend to replace your filter every 2-3 days (if you are using it for several hours a day) or 18-24 hours of total use.<br> if you use it in a particularly dusty environment (eg. doing woodworking, gardening, etc) would be better to replace your mask with a new filter after you finish that activity.<br>