Abstract: A method and a device for air filtration, whereby air is drawn from the surroundings of a house through air filters including at least a portion of the wall of the house and is blown out to the surroundings in cleaned condition. Air is drawn through at least two different parallel coupled filter units, which clean the air in a corresponding number of ways. Predetermined fractions of total drawn-in air passes through the respective different filter units and thus are subjected to corresponding cleaning by the different filter units being adjusted to each other with respect to pressure drop. The differently cleaned fractions are mixed before exhaust.