The present invention relates to a method for purifying process waste gases by introducing them into a waste gas purification system that includes a reaction chamber and by post-treating the reaction products that leave the reaction chamber in a washing or sorbtion chamber with an associated washing agent circuit. The type and amount of harmful substances in the process waste gas are continuously measured before the waste gases enter the waste gas purification system. In addition, the type and amount of harmful substances in the reaction products that leave the waste gas purification system are simultaneously determined directly at the exit of the system and the measuring signals are used to regulate the operating parameters of the waste gas purification system.