A method for operating a power plant is disclosed. The power plant comprises a power machine and a flue gas flow path following downstream of the power machine. A flue gas flow path is scavenged with fresh air before the flue gas flow path is acted upon with flue gas. To carry out the scavenging operation, air is extracted from a pressure accumulator and the air is introduced into the flue gas flow path downstream of the power machine. The power machine can be an exhaust gas heat exchanger.