PURPOSE: To permit the collection of gas smoke from a plurality of generating sources efficiently by a method wherein the opening degree of a plurality of control dampers for preventing the leakage of gas smoke is regulated by remote control from the operating chamber of a ceiling crane.

CONSTITUTION: The remote control panels of all control dampers are installed in a ceiling crane. The operating chamber of the crane is in a high place and, therefore, a plurality of generating sources can be seen therefrom whereby gas smoke can be sucked most efficiently by operating the control dampers. When operators in charge of a furnace are not waiting upon charging mat into a converter, for example, one series of operations of not only the regulation of the opening degrees of respective dampers but also the opening and closing of a mat charging port, the setting of a traversing hood and the like can be effected from the operating chamber of the crane by remote control. According to this method, the leakage of sulfur dioxide gas smoke can be prevented perfectly.