The HEPA Filter in the AP-1008CH air purifier is designed to remove 99.95% of particles as small as 0.3 micron. It helps to remove tobacco smoke, virus, germs and micro-dust. The special design of the HEPA pleating allows for a higher volume of airflow. Because the HEPA filter has been treated with Nano Silver and Cathechin, it is anti-bacterial. It is recommended that the HEPA Filter be replaced every 12-24 months.