Body relief valve flap

A valve for use in ventilation of the passenger compartment of a motor vehicle comprises a housing defining a plurality of through flow passages with separate flap valve elements pivotally mounted adjacent each through flow passage. The valve elements are adapted in a first position to overlie the associated through flow passage for blocking flow, but when pivoted toward a second position, they open to permit flow. The flap valve elements are each pivotally mounted by separate hinges which act to bias the valve elements toward the first position with a preselected force. The hinges on separate ones of the flap valve elements are arranged to provide different preselected biasing forces such that the number of valve elements moving toward the open position at any point in time depends upon the then current level of pressure of fluid on the upstream side of the valve.