A two-stage process is provided for purifying off-gases from a high-pressure melamine plant. The series of slice measurement sequences is designed to allow a separation of a first material from a second material that has a defined chemical shift relative to said first material, and the position of a measurement slice with measurement data for the first material is spatially shifted relative to the position of a measurement slice with measurement data for the second material. The knowledge database simulates a human inspiration source that is influenced by sensibility by classifying externally collected knowledge data depending on the degrees of correlation with the emotion states, and accumulates the knowledge data.