an arrangement is provided for cleaning pipelines and especially ventilation pipes and ducts in buildings , and includes a nozzle connected to a supply conduit through which a pressurized medium can flow . the arrangement includes a nozzle opening directed back toward the supply conduit . the nozzle opening is in the form of a large continuous annular gap which extends along the periphery of the nozzle and is connected to the supply conduit and the source of a pressurized medium . the gap directs the medium toward the inner walls of the pipe or duct and effects a cleaning of the inner walls . the nozzle is moved into the pipe or duct as a result of reaction forces generated from discharge of the pressurized medium through the nozzle opening .