neglectable rest amounts of helium remain at that time the valve 21 is closed and the cooled metal articles are transported out of the cooling chamber 10 then being ready for the cooling of next batch of metal articles the compressor 25 continues to evacuate the buffer tank 23 until a pressure of 1 bar has been reached then also the valve 24 is closed thus it is both during the evacuation by means of the buffer tank 23 and in particular during the following 34 lifting 34 of the remaining helium essential that the outlet member 19 is arranged in the upper part of the cooling chamber 10 to enable the utilization of the smaller weight of the helium compared to the nitrogen the upper limiting wall of the cooling chamber 10 may possibly be inclined or have a conical or pyramidal shape the outlet member 19 being arranged at the highest point of location the purification process for the gas used during the cooling functions according to the following the gas mixture from the cooling chamber 10 is pressurized by means of the compressor 25 to a pressure of approximately 30 bar and transported through the filter 26 protecting the subsequent purification columns 29 30 against possible oil residues or the like from the compressor 25 the valves 28 and 34 are now closed whereas the valves 27 and 33 are open thus the gas mixture will be supplied from below through the purification column 29 the nitrogen present.