Removal of soot or dust deposits in a duct involves providing suction heads at the inlet and outlet of the duct. The positions of the suction heads can be changed. Also claimed is the equipment used in this method. Suction heads at inlet and outlet may move independently or synchronously at the same or at different pressures. Items in the duct, for which this system was particularly designed, are honeycomb or plate catalysts or heat exchangers. A controller moves the suction heads in a two-dimensional co-ordinate path. Clearly, flexible hoses connect the heads to the suction side of a common fan. Valves in these hoses permit variations in the suction at each head. Alternatively, attachments to the heads allow variation of pressure and throughput.
