A combination exhaust gas post treatment/muffler device in the exhaust gas section of an internal combustion engine is provided. The exhaust gas post treatment within the muffler, which forms sulfuric acid, takes place in at least one exhaust gas post treatment/muffler module, and only that housing thereof through which flows exhaust gas that is to be cleaned is produced from ferritic or austenitic stainless steel, thus making it possible to produce the outer walls of the muffler, as well as any inner element thereof, such as a transverse wall, that is disposed externally of the exhaust gas post treatment/muffler module of unalloyed sheet steel that is coated with aluminum or some other material.