a flap - type pressure relief valve particularly intended for relieving overpressure conditions in a vehicle passenger compartment includes a frame having an integral peripheral sealing gasket that is formed on the frame by being injection molded directly thereto . the frame is molded from a relatively rigid plastic and the gasket is molded from a plastic that is significantly more resilient and flexible but selected to permanently bond to the plastic of the frame when brought into contact therewith under injection molding conditions .