Two-Stages of odor protection: the CPZ filter is designed to assist in the removal of strong, powerful odors found in new carpeting, flooring, paint, etc. Each element of the CPZ filter helps to adsorb gases, odors and VOC's. The carbon pre-filter is included to help capture large airborne particles* as well as help with the removal of common household odors. For use in Honeywell Models 17250, 41200, and 61200 CPZ filter should be replaced every 18 months Carbon Prefilter should be replaced every 1-3 months