For a nearly maintenance-free and hygienic operation. The Venta Hygienedisk is an accessory for the following air washers: Professional AW902 and AH902. It contains a silver-coated ion exchange granulate for water softening. This prevents hard lime deposits in the water basin. The addition of hygiene agents and water softeners becomes unnecessary. It descalers the water. Low maintenance effort. Easy to replace. Made in Germany. Note: Depending on water hardness, water quality, device usage duration, and daily evaporation performance, the Hygienedisk should be replaced at least every 3 months.