an automotive radiator made by the combination assembly of aluminum tubes and thin plates ( of a weight of 1 . 4 kg , and of dimensions of 600mm × 400mm × 36mm ) was coated , for the purpose of machine processing and assembly , by a light oil lubricant , ignition point of which is 83 ° c . ( coc ), upper and lower explosing limits of which are assumedly 7 volume % and 0 . 6 volume %, and density of which is 0 . 79 g / cm2 . unless the lubricant which is an oily substance , is removed , abutments between the aluminum tubes and thin plates can not be brazed . therefore , the oily substances were removed in accordance with this invention method , before the radiator was subjected to a brazing operation . the method was carried out by means of a belt conveyor type continuous furnace which is illustrated in fig1 . in the drawing , numeral 1 indicates a tunnel - like heating chamber surrounded by heat - insulation materials . the chamber has at its both ends an inlet and outlet , and metallic mesh belt 5 circulating therethrough . the above - mentioned radiator assembly 2 was carried upon the belt and traveled through the heating chamber . the heating chamber was heated by a burner 3 which is as mentioned above for burning a fuel gas and for generating a reductive gas . the burning of the fuel gas is made in a plurality of closed radiant tubes for radiantly and indirectly heating the heating chamber . from a heat - source 7 to the burner 3 , there was sent a propane gas mixed with air . the combustion of gas in the burner was controlled so that both of isolated oxygen and carbon monoxide remaining in a combustion exhaust gas were maintained as low as possible . the exhaust gas was sent through a pipe 6 to a refinery column 11 in which the gas was cooled and dehydrated . thereafter , the gas which is neither flammable nor explosive , was recycled to the heating chamber as its heating atmosphere . numeral 4 indicates agitators for making a chamber temperature even through the heating chamber . the heating atmosphere in the heating chamber 1 which contains oily substances evaporated from the radiator assemblies , was partially led outside of the chamber through an exhaust tube 12 , and to a gas and liquid separator 8 . the liquidous oil substances separated by the separator 8 were returned through a pipe 9 and reused as a heat - source . on the other hand , the gas separated by the separator was recycled through a pipe 10 to the refinery column 11 through which it was sent to the heating chamber as its atmosphere . numerals 13 indicate pilot flames for safely burning out flammable substances which are contained in a gas dissipated about the inlet and outlet of the heating chamber . the atmosphere within the heating chamber 1 was kept at 180 ° c ., and the radiator assemblies 2 were passed therethrough in 15 minutes , whereby oily substances of 66 g were removed per each assemblies . these radiator assemblies , oily substances of which had been removed , were subjected to a separate brazing operation . the brazing was made satisfactorily . in fig2 in which the parts same to those illustrated in fig1 are represented by same numerals , burners 3 in this example 2 are however not of closed radiant types but are open to the heating chamber 1 . accordingly , combustion exhaust gas which has been produced by the burners 3 by burning a combination gas of air and propane sent from heat - source 7 is released to the heating chamber to make a heating atmosphere together with another gas released to the chamber through pipe openings 19 which will be described below more in detail . the heating atmosphere which is kept at 180 ° c . and through which the above - mentioned automotive radiator assemblies are passed , heats them and evaporates oily substances from them . and , the heating atmosphere which thus contains the oily substances , are led via an exhaust fan to a combustion chamber 14 in which a combination gas of propane and air sent from the heat source 7 is burnt by a burner 21 to about 400 ° to 700 ° c . into this burning gas , there is sent the above - mentioned heating atmosphere , whereby its oily substances are burnt out . a part of the combustion exhaust gas thus produced in the combustion chamber 14 is released to air by an opening 16 in order to keep a pressure in the combustion chamber constant , and its major part is led through an opening 15 and a pipe 18 to the above - mentioned pipe openings 19 so that it is reused as the heating atmosphere . before returning to the heating chamber the combustion exhaust gas which has been heated to 400 ° to 700 ° c ., it has to be cooled down to about 180 ° c . which is a working temperature of the heating chamber 1 . the exhaust gas is cooled down by sucking into the gas from a pipe 17 an atmospheric air of room temperature at such amount that when it is recycled into the heating chamber , a density of oily substances contained in the heating atmosphere in the chamber as a whole shall not exceed its low explosion limit of 0 . 6 %. in fact , the density was kept about 0 . 06 % in this example . or , alternatively , the gas is cooled by a heat exchanger 20 , cooling medium of which is an atmospheric air of room temperature . the air cooling medium which has been heated up , can be utilized as an air additive in the combustion chamber 14 . in this example 2 too , oily substances were satisfactorily removed , and the automotive radiator assemblies were brazed well .