This true HEPA Filter captures 99.97% of airborne particles as small as 0.3 microns, including pollen, dirt and cigarette smoke. It provides built-in shielding from the foul smell on the True HEPA filter. Compatible with Fellowes AeraMax 300 Air Purifier. With normal usage, it is recommended that you change your filter every 12 months to keep your air purifier running at peak performance. A filter change indicator on your Fellowes AeraMax hundred Air Purifier conveniently notifies you when it's time to replace your True HEPA filter.