This filter is a PM2.5 (2.5 micron, particulate matter) 5-layer, activated carbon filter, which is used (inside a mask) to protect your mouth and face from dust, haze, allergies, smoke, pollution, ash, poller, hazardous chemicals and heavy metal particles. Replace the filter after one week of use, when any physical damage occurs to the filters or anytime the filter becomes damp or moist.