True HEPA Filter for Fellowes 190 Air Purifiers, 10.31 x 13.37 Captures 99.97% of airborne particles as small as 0.3 microns. AeraSafe™ antimicrobial treatment provides built-in protection from the growth of odor causing bacteria, mildew, and fungi on the filter. Compatible with AeraMax® Air Purifiers. Indicator notifies you when it's time to change filter. With normal usage, it is recommended that you change your filter every 12 months.