Dirty air is drawn into the air purifier through the inlet grill. Some of the units have a washable pre-filter that traps larger airborne particles. Air then passes through the carbon filter with help reduce odors and captures larger particles. After passing through the carbon filter, the air then passes through the HEPA filter made of tightly woven fibers. Some units have electronic ionizers which further assist in particle removal. The fan then redistributes the filtered air throughout the room.