the invention concerns a device for heating plastics profile sections , in particular for heating pvc profile sections , the device comprising a box for holding the profile section . said box has a support plate , side panels and a lid , as well as means for feeding hot air to one end face of the profile section so that it can flow internally and externally past the profile section . efficient operation is attained in that a return duct is provided for returning and reheating the air when it has flowed through or around the profile section in order to form a closed air circuit .