It is recommended to change the Carbon filter in your air purifier every 3 months, so the Leitz TruSens Z-1000 Replacement Carbon Layer - 3 pack, is a must. Filter replacement is essential for your air purifier to perform at its best. The activated carbon layer removes certain gases and odours from the air. The carbon pre-filter not only captures odours and gases, but it also offers the first level of defence against dust and pet hair.. Replacement Carbon Filters. Pack of 3. Compatible with Leitz TruSens Z-1000 Small Air Purifier. For best results, replace carbon filter layer every 3 months. Change indicator light is displayed on purifier when filter needs to be replaced *Please note that this product is delivered direct from our supplier and may take a little longer to arrive