The Blue Pure 311 Combination Particle + Carbon filter protects against both gaseous and particulate contaminates. Advanced polypropylene filter media removes particle pollutants from your indoor air, such as pollen, dust, and pet dander. At the same time, a layer of activated carbon mesh traps light household odors from pets, cooking, smoke, and more. The 360-degree design allows the filter surface area to be over 13 square feet in size.