a gas inlet port a gas chamber connected to the gas inlet port and a reaction agent passage defined in the gas chamber by a louver device in an intermediate portion and a lower portion having a regulatable discharge device the reaction agent passage of the intermediate portion is communicated with a lower end of the reaction agent storage portion form a single column of reation agent the regulatable discharge device regulates the moving speed of granular reaction agent supplied through the reaction agent supply port and allows it to move down by gravity to fill the single reaction agent column while filtering and adsorbing dust and toxic substances contained in upwardly moving gas therethrough application_number US 75847591 A description in order to clarify the principle of the present invention some experiments conducted by the inventors will be described first with reference to fig5 to 7 and then embodiments of the present invention will be described in detail in fig5 which shows an apparatus used in these experiment it includes a first dust collector 71 a second dust collector 72 series connected to the first dust collector 71 filter material 73 filter material supply tanks 74 and 75 a filter material discharge tank.