by charging the dust positive to thus cause electric repulsion between the fibers and the dust in a dust removal step in this case a dust collecting effect is enhanced by charging a dust collector itself and or air negative because of electric attracitve action of the collector and air hereinafter the present invention will be explained in more detail by away of experimental examples that follow to which examples the invention is in no way limited as was illustrated by fig1 about 12 g of bedding feathers 1 were wrapped in a polyester net 2 and those were surrounded by a negative ion generator 3 those were placed in a vinyl bag 4 and an inlet 5 was fastened to isolate the external atmosphere electric power was supplied to generate negative ions with which the feathers were charged for one month as a negative ion generator 34 ion roll tradename manufactured by rakkasan co ltd 34 generators having an output of 1 5 w and 0 2 w were served for comparison a similar experiment was carried out with the exception that the feathers were not subjected to the treatment by the negative ion generator after one month as shown by fig2 g of treated and non treated feathers were placed in 500 ml conical flasks 6 respectively which were sealed with silicone rubber corks 8 having a.