The Meaco Deluxe 202 Calcium Carbonate Water Filter is attached to the water tank cap. The filter can be regenerated at any time by placing the filter in water that is 5% salt for 24 hours. 

The Calcium Carbonate Filter will need replacing when white dust deposits (limescale) start to form around the humidifier. They come in a pack of 3

If the plastic bag around the filters has been opened, this product cannot be returned for health and safety reasons.