is described in detail fig5 illustrates a situation in which the occupant qualifying means has determined a small vehicle occupant the control means in this case does not confirm the activating unit 24 so that the tensile means 22 is not released due to the shortened length of the tensile means 22 at the end of the deploying operation the latter exerts a tensile force f on the flap 20 at the connecting point in the outer portion 30 cf fig2 and 3 this force defined by the deployment of the upper portion of the knee airbag 10 is so strong that the seam 26 tears the force transmission via the tensile means 22 is optimal thanks to the acute angle u03b1 to the effect that the flap 20 is efficiently peeled off the airbag sheath 14 by the tensile means 22 by the partial detachment of the flap 20 from the airbag sheath 14 the upper portion of the knee airbag 10 can completely deploy with the tensile means 22 keeping the flap 20 away from the exhaust orifices 18 thus the exhaust orifices 18 are released and gas can escape from the knee airbag 10 the internal pressure of the knee airbag 10 is thus reduced so that the impact of the knees of the small vehicle occupant on the fully inflated knee airbag 10 is dampened fig6 illustrates the same situation as fig5 however in the event that the occupant qualifying means has established a normally sized or tall vehicle occupant in this case the control means actuates the activating.