A method for gasifying carbon-containing materials in which the material for gasification and oxygen, usually in the form of air, are supplied to a gas generator where the gasification takes place in a fixed bed reactor. The product gas is drawn off via a product gas line and introduced into a hot gas filter. A filter, preferably provided with filter candles, removes solids such as particles not yet gasified, ash and foreign bodies, while clean gas passes through and is taken off via a clean gas line. An outlet is provided in the bottom region of the hot gas filter to remove residual solids. The hot gas filter is supplied through a line with oxygen, preferably in the form of air, in its middle height region, between the filter bottom and the outlet.