Abstract: A circulation fan for circulating air in the baking muffle of an oven in which a conductive connection is made between the drive shaft and the back wall of the baking muffle whereby the RF energy passing outward over the surface of the drive shaft is short-circuited via the back wall of the baking muffle. The conductive connection is in the form of a spring element, e.g. a clamping member or a disk spring, whereby manufacturing and operational variations are compensated for. If the portion of the drive shaft located outside the baking muffle is roughened and/or covered with an electrically poorly conducting coating, further damping of the escaping RF energy is obtained.