to allow for easier opening of a refrigerator door , a pressure relief system is provided to relieve a pressure differential or vacuum that develops due to operation and use of the refrigerator . the pressure relief system includes a check valve having an orifice with a flexible membrane . an insulation portion of the pressure relief valve , which is foamed into the cabinet , spans from the fresh food compartment to a top of the cabinet and directs air towards the rear cabinet liner for moisture condensing measures . the pressure relief assembly also includes an adapter which mounts to the cabinet top and provides a mounting surface for an air return assembly .