Honeywell HAC-504 Humidifier Replacement Filter, Filter A Filter Removes Minerals & Pollutants From Water Inhibit Growth and Migration of Mold and Bacteria Replacement Wicking Filter Pads Protec treated filter inhibits up to 99% of mold growth Antimicrobial treatment helps prevent the growth and migration of mold, fungus and bacteria on the filter Updated model of the HAC-504AW, the HAC504V1 now features a new optimized filter design that maximizes moisture output.