An airbag includes an outer shell defining an interior, at least one vent opening structured to enable fluid communication between the interior and an exterior of the airbag, and a divider dividing the airbag interior into an upper chamber and a lower chamber. The divider is deflectable in a first direction toward the lower chamber and in a second direction toward the upper chamber. A vent cover is coupled to the at least one vent opening and to the divider so as to close over and restrict a flow of gas through the at least one vent opening when the divider is deflected in the first direction, and so as to permit the vent cover to open so as to enable an unobstructed flow of gas through the at least one vent opening when the divider is deflected in the second direction.