Abstract: A method and device for thermal activation of tube-shaped packaging sleeves made of cardboard/plastic composite material, wherein a hot gas is applied to the tube-shaped packaging sleeve by a heating device in order to produce the base or the head of the packaging. To achieve even heating for the activation of the contact surfaces with production using simple construction, wherein the energy required for the activation process is used as completely as possible for the heating of the surfaces to be activated, the heating device is placed into effective contact with the surfaces to be activated by the heating device being moved inside the tube-shaped packaging sleeves for activation. The heating device has at least one nozzle element with an outlet opening, the external shape of which nozzle element corresponds to the internal shape of the end of the tube-shaped packaging sleeve to be activated.