Abstract: A method and apparatus for minimizing disturbances caused by depositions on a feeding apparatus for a combustion or gasification plant. Secondary air is fed via perforated tubes 13 which by affecting the emission levels of the process with longer or shorter time intervals are inserted and withdrawn from the chamber, while being cleaned from slag, dust and other deposits outside the chamber by wire brushes 21. The combustion process may continue by using the remaining tubes while one or more are being cleaned.