A method is provided for surveillance and balancing of coal dust supply through channels to coal furnaces. Data is gathered from results of automatic sample collections of coal dust particles conveyed by air current in circular channels from a coal crusher to a coal furnace. Data is processed for generating control parameters for a cross-section area regulating draught control unit in each of the respective channels. Each control parameter is adapted to control a respective draught control unit to change cross-section of the channel in size and direction for reducing differences in coal dust conveyance of channels. A completely or practically constant surveillance and balancing of coal dust supply in two or more channels to a coal furnace can be made automatically, resulting in reduced emission and/or improved fuel economy. A collector and a draught control unit apparatus for carrying out the method is also provided.