12''x40'' Funk Filter Carbon Air Filter12''x40'' Funk Filter Carbon Air Filter. 1700 CFM Funk Filters consist of an aluminum housing packed with a high performance virgin activated carbon. These are available in a wide range of sizes making them ideal for smaller tents and large commercial greenhouse applications. They remove 99. 5% of all odors and most other airborne particles to keep your plants safe. The granular carbon has a 1050 mg g iodine number providing more surface area and thus