A process for producing a chalcogen-containing compound semiconductor includes providing at least one substrate coated with a precursor for the chalcogen-containing compound semiconductor in a process chamber; heat treating the at least one coated substrate in the process chamber, wherein during a heat treatment, a gas atmosphere comprising at least one gaseous chalcogen compound is provided in the process chamber; removing the gas atmosphere present after the heat treatment of the at least one coated substrate as a waste gas from the process chamber; cooling the waste gas in a gas processor, wherein a plurality of gaseous chalcogen compounds-present in the waste gas after the heat treatment of the at least one coated substrate are separated in time and space from one another from the waste gas by respective conversion into a liquid or solid form. Further provided is a device designed to carry out the process.