A computer-implemented method and device includes obtaining a first electrical signal on a basis of an interaction between one or more odor substances in a gas and at least one first odor sensor, filtering at least one predetermined odor group out of the gas and obtaining a filtered gas, wherein the odor group comprises at least one odor substance that is to be filtered out, obtaining a second electrical signal on the basis of an interaction between one or more odor substances in the filtered gas and the first odor sensor and/or at least one second odor sensor, determining a difference between the first and second electrical signals, and assigning this difference to the odor group.