Genuine Blueair Replacement filter compatible with Blue Pure 311 Auto air purifier. The 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. Unlike look-a-likes, authentic Blueair replacement filters are designed to maintain premium performance over time and ensures your warranty remains intact. For optimal performance, replace the filter about once every six months when used 24 hours a day. The twist-and-change filter is easily removed and replaced and is recyclable at the end of its service life. Please check your local recycling facilities for availability.