This filter combines the low resistance, high dust holding capacity of a pleated filter with the odor removing abilities of activated carbon. The base filtration medium is polyester synthetic fiber. It has a generous 100% add-on of activated carbon by weight. (Weight of activated carbon equals the weight of the media to which it is adhered.) As odor producing gases come in contact with the activated carbon in the filter, they are adsorbed...trapped and held in millions of microscopic carbon pores.