An occupant protection apparatus comprises an inflatable airbag with a panel, the panel including a first vent opening that permits inflation fluid to escape out of the airbag; and a valve sheet including a second vent opening movable relative to the first vent opening, the valve sheet having opposite ends that are each fixed to a surface of the airbag. One end of the valve sheet moves with the panel during inflation of the airbag to move the second vent opening relative to the first vent opening. The apparatus also includes a valve guide or envelope to guide movement of the valve sheet relative to the panel, the valve sheet is capable of sliding between the valve guide and the panel. Both ends of the valve sheet remain fixed to the panel during and after inflation of the airbag. The valve sheet includes a tear tab to temporarily retain the valve sheet to the panel.