The Stadler Form V-010 Viktor room air purifier replacement filter pack is designed to be used with the Stadler Form Viktor room air purifier. The Viktor room air purifier creates the purest air possible in your home. Every 6 months or so, depending on air quality, the preliminary filter and activated carbon filter in your air purifier must be replaced. Inside the Stadler Form V-010 Viktor room air purifier replacement filter pack, the preliminary filter retains large particles such as pet hair, pollen and dust. It protects successive filters against large objects and optimizes their function. The activated carbon filter adsorbs gases and odors from the air, eliminating unpleasant odors such as fish, cheese and smoke.