NOVELTY - Device comprises: a closable preparation chamber (2.2) with catalyst and temperature adjustment device; functionally integrated process gas compressor (2.3); equipment (2.4) for measuring inflow of treatment media of process gas, where the equipment is connected functionally to treatment chamber (1.1) of industrial furnace (1), to preparation chamber, and to process gas compressor; and switching unit for controlling and adjusting at least one parameter of process gas to be prepared in preparation chamber.    USE - The device is useful for preparing process gases (claimed) for heat treatments of metallic material/workpiece in industrial furnaces.    ADVANTAGE - The device: performs heat treatment process in an efficient and environmentally friendly manner; avoids streaks or inconsistencies in the heating chamber which are normally seen when natural gas is introduced into the chamber; and prevents undesirable local over-carburization, which are caused by unbalanced carburization due to the methane dissociation.    DETAILED DESCRIPTION - Device comprises: a closable preparation chamber (2.2) with catalyst and temperature adjustment device for preparing a process gas; a functionally integrated process gas compressor (2.3); equipment (2.4) for measuring the inflow of treatment media of the process gas, where the equipment is connected functionally to the treatment chamber (1.1) of a industrial furnace (1), to the preparation chamber, and to the process gas compressor; and a switching unit for controlling and adjusting at least one parameter of the process gas to be prepared in preparation chamber for the purpose of feeding the treatment media, feeding the prepared process gas into treatment chamber of the industrial furnace, and the carbon activity (C level), and extracting at least one of the treatment media.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view an industrial furnace operated using the device.    Industrial furnace (1)    Treatment chamber (1.1)    Preparation chamber (2.2)    Process gas compressor (2.3)    Equipment (2.4)