Honeywell Household Odor & Gas Reducing Pre-filters are ideal for capturing harmful gasses such as ammonia and other volatile organic compounds. Pre-Filters also perform exceptionally well in deodorizing the air and reducing odors with an activated carbon and zeolite. Absorbing common household gasses and fumes, Pre-Filters will capture larger particles such as dirt, lint, fibers and pet fur. It is recommended that you replace your filter every 3 months. This package includes 2 pre-filters. It should be noted that Tower air purifiers require 2 filters. Establish an unrivaled breathing experience for you and your loved ones with Honeywell and their second to none series of Filters.