Only the Van Ness Zeolite Air Filter offers a real solution - Zeolite, a natural mineral which actually removes ammonia odors from the air. The patented system of air purification, Zeolite-coated filter pads soak up ammonia gas on contact. Enjoy true odor control with the Van Ness Zeolite Air Filter, the all natural ammonia remover that absorbs urine odor before it leaves the box. The replacement filter works with Van Ness Enclosed Litter pans.