Regular filter changes in the Airfresh Clean 400 air purifier ensure consistently clean air. The replaceable filter is the main component of the 4-stage cleaning system and removes 99.95% of particles such as allergens, viruses, and pollutants from your indoor air. Larger dust particles and hair are removed from the air by a pre-filter, a high-quality HEPA filter reduces pollen, bacteria, and fine particles, while an activated carbon filter neutralizes unpleasant odors and gases. To maintain high cleaning performance, the filter change indicator on your air purifier will signal after approximately 4,000 hours of operation that the filter needs to be replaced. It can be quickly and easily removed and reinserted.