The new PETKIT PURA AIR Smart Odour Eliminator , eliminates smells on the spot. With built-in infrared sensors, it automatically releases negative ions, and deodorants to effectively eliminate odours, bacteria, and formaldehyde when pets enter the effective area. Natural scent extract from 20 different plants, makes it non-toxic and refreshing. One filter set can last up to 90 days. For the best result, place the PURA AIR Smart Odour Eliminator around the PETKIT cat litter box series, or the PETKIT PURA dog training tray.