Abstract: A combination of a horizontal-flow electrostatic precipitator having a first inlet for a gas to be cleaned, the first inlet having a reactangular configuration lying substantially in a vertical plane and a diverting and distributing device for feeding vertically downwardly arriving gas to the first inlet, the device having a downwardly divergent diffuser provided with a second inlet for receiving the gas and being disposed adjacent the first inlet. A housing constructed to define a downwardly convergent inlet passageway connected to the diffuser receives the gas therefrom, the housing being open laterally in the direction of the first inlet and in flow communication therewith over the entire cross-section thereof, with structure forming a preliminary dust-accumulating bin below the housing and connected thereto.