The invention relates to a heat exchanger, especially a regenerative heat exchanger, which comprises a storage heater arranged as a rotor; the rotor is kept to be able to rotate around the central rotation axis, and at least one air volume flow of heat energy passing through the rotor is transferred to at least another one air volume flow passing through the rotor. The heat exchanger also comprises at least one surrounding seal for sealing the circumference of the rotor; for improving the sealing of the heat exchanger, the surrounding seal is mounted on a surrounding shield of the rotor from outside by sealing mode, preferably located at the region on a working surface side of the rotor; wherein the surrounding seal is disposed flexibly in the region.