relatively small resistance to an exhaust stream flowing through the clearances thus pressure loss of exhaust is small the dusts contained in the exhaust come into contact with the porous dielectric material forming walls of a narrow and bended passageway and are mechanically collected charged by the adherence of ions created due to the slipping or a high voltage between electrodes and collected and retained by the porous dielectric material by the electric field formed between electrodes as is known the electric field formed between electrodes is produced not only in portions where the electrodes are opposed each other but bulges towards both sides thereof and also greatly bulges externally of the porous dielectric material therefore as shown in fig8 the electrodes can be copper wires 23 23 39 instead of foils 1 in the present invention the filter element 2 is merely forced into the bag and spread fully over the passage such as an exhaust duct by its own resilient force therefore the dust collector can be easily installed irrespective of the size and section of the existing gas passage 2 since both sides of each of the electrodes are covered with the porous dielectric material even if the filter element 2 is randomly packed there occurs no possible short circuiting between the electrodes and handling thereof is extremely easy 3 despite that the filter element is forced in a complicated shape it is in the form of a narrow strip and therefore one terminal for application of voltage will suffice thus the whole construction of the.