10 includes at least one preferably two to five and in the embodiment shown here two modular treatment chambers 12 13 arranged one after the other in a row the interior of the housing 10 is subdivided by the treatment chambers 12 13 into two fields arranged one after the other the housing 10 is not subdivided and surrounds all treatment chambers 12 13 a circulating device or in other words a device for guiding wet steam in a circulation which is identified as a circulating process is provided in each treatment chambers 12 13 it has a circulating fan 14 each treatment chamber also has a heating device which is not shown in fig2 and nozzle boxes 15 with nozzle openings directed toward the product web 1 in one treatment chamber 12 13 several for example two nozzle boxes 15 can be arranged above and below the product web 1 transversely over the product web the nozzle openings are preferably formed as slots a transporting device has guiding rollers 16 17 in the inlet lock 9 and guiding rollers 18 19 20 in and downstream of the outlet lock 11 in addition the transporting device has a roller conveyor with two guiding rollers 21 22 and a pulling roller 23 in the region in which the both treatment chambers 12 13 abut against one another the roller conveyor thus extends over the half of the transporting path of the product web 1 from the inlet slot 27 in the front wall 26 to the outlet slot 29 in the rear wall 28 the both guiding rollers 21 22 have identical sizes and are arranged close to each other at the same height the arrangement of the guiding rollers 21 22 the last guiding.