line comprising 3 fibering machines 1 2 3 placed in the same row these fibering machines 1 2 3 consist for example of centrifuges rotating at great speed provided at their periphery with a large number of orifices by which the molten material preferably glass escapes in the form of filaments which then are drawn into fibers by a concentric gas stream parallel to the axis of the centrifuge emitted at high temperature and speed by an annular burner optionally other fibering devices well known in the art can be used which all make possible the forming of a core of fibers centered on an axis cores formed by the drawing gases and especially the gases induced in a very large amount the reception of fibers intended to separate the latter from the gases is obtained by a gas permeable endless belt 4 given continuously a hood 5 laterally delimits the collecting zone of the fibers the suction of the gases is obtained by independent boxes 6 under partial vacuum a box 6 is joined here to each fibering machine 1 hood 5 is closed in as airtight a way as possible and for this purpose is provided at the output with a press roller 7 optionally assuring a certain traction on the felt to help extract it from the hood according to the invention a collecting zone zi delimited below by endless belt 4 corresponds to each fibering machine 34 i 34 i 1 2 3 these zones zi are increasing with their index and therefore are all the larger as they are close to the output a reception has been proposed comprising as many.