The invention relates to a method for producing sulfuric acid, wherein, in a production mode of the method, sulfur is oxidized in a first oxidation stage in order to produce sulfur dioxide and wherein the sulfur dioxide is catalytically oxidized in a second oxidation stage in order to produce sulfur trioxide. The sulfur trioxide is absorbed in at least one absorption stage. In the production mode, process gases are discharged from the absorption stage that is last in the flow direction. In a stand-by mode of the method, at least one heating stage for heating the processes gases is activated. The process gases exiting the absorption stage are conducted to the heating stage, and the processes gases are circulated through the heating stage, the second oxidation stage, and the absorption stage.