Abstract: A filter for gases, particularly for ventilation, is provided with elongated flow channels (3) which are at least partly formed by superimposing material layers (1) between which the flow channels (3) are formed so that their starting ends are open to a gas inlet (A) and their terminal ends are open to a gas outlet (B), wherein the gas flow between the starting ends and the terminal ends in the channels (3) is arranged parallel to the planes of the material layers (1), and the layers contain an adsorbent in which impurities are adsorbed from the flow in the channels (3). The material layers have, on top of each other, at least one support layer (1a) and a porous adsorbent layer (1b) kept in place by the support layer (1a). The channels (3) are formed between spacers (2) which contain porous adsorbent material, constitute elevated areas on the material layers (1), and keep them separate at the channels (3).