Honeywell Household Odor & VOC Reducing K Type Air Purifier Pre-filter, 2 count; Take your pet pal’s air purifier up a notch with Honeywell Household Odor & VOC Reducing K Type Air Purifier Pre-filters. These potassium permanganate calcite pre-filters are designed to deodorize the air, reduce animal odors and absorb household gases and fumes. They include a cutting template and are crafted to trap flying pet fur, dust, lint, fibers and harmful volatile organic compounds (VOCs). You should replace your pre-filter every three months for the best performance.