Puredry PD 20L Replacement Carbon Filter Set of 3 This high performance activated carbon filter removes odors, smoke, chemicals and more from the air entering the dehumidifier. A must for allergy and asthma sufferers, this filter is lab tested to trap 99.97% of harmful airborne particles, bacteria, germs and pollutants. The filter must be changed every 3-4 months, depending on the pollutants in the application area. Provide in airtight package 3 pieces, can ensure one year use. Dimensions Height, Length, Width 24*11.4*0.3 cm