Product description Replacement HEPA filters for Aironic ® BD-AP40 Filter Lasts about 9 to 12 Months Measures 9-1/2"W x 10-1/4"L x 1"D Includes One replacement Aironic ® True HEPA filter PP filter: Traps particles over 20um in the air, thus extend the life time of HEPA filter. The HEPA filter: Traps particles over 0.3um in the air (Allergens, pollen, dust, smoke, pet dander, etc.) Activated carbon filter: Absorbs smoke and odours True HEPA filter eliminates more than 99.7% of micro sized airborne pollutants larger than 0.3 micron. Also includes pre-filter, cold catalyst filter and activated carbon filter. dimensions are 23.5cm by 22.5cm Advanced multi-layer 4 filter system purifies indoor pollutants including bacteria, harmful gases, viruses, animal dander, unpleasant odours, fungi, cigarette smoke and pollen.