Intellipure's proprietary 6-stage VOC adsorption pre-filter is designed to remove harmful gases, odors, and more from your space.  It contains a proprietary blend of materials, including potassium permanganate, zeolite and carbon. Based on typical use, we recommend replacing this filter every 3-6 months. Please visit our FAQ page for directions on how to replace your filters. Contains (1) pre-filter replacement per package.