Abstract: A check valve is provided with first and second housing components that are telescoped together to define a valve housing having an inlet, an outlet and a valve chamber therebetween. The valving element is disposed in the valve chamber for movement between a first position where the valving element seals the inlet to the valve chamber and a second position where the valving element permits flow from the inlet, through the valve chamber and to the outlet. A disk spring has a central support secured to the valving element and an outer support secured between the first and second components of the housing. The disk spring is disposed to bias the valving element into a closed position. However, sufficient gas forces in the inlet will overcome the forces of the spring and open the valve. The spring is asymmetrical to prevent noise attributable to fluttering of the valving element and to achieve a more rapid opening response.