Airbag having a pressure responsive vent

An airbag comprising:

• a fabric enclosure;
• a vent in the fabric enclosure;
• and
• a flexible membrane fastened around part of a periphery of the membrane to an inner surface of the fabric enclosure adjacent to the vent to define a flow passage having a free end through which inflation gas is vented to atmosphere during inflation of the airbag, the airbag having a pre-deployment condition wherein a tongue portion of the membrane extending away from the free end overlies an inner surface of the fabric enclosure and a distal end of the tongue extends past an end of the vent closest to the free end, the distal end being unrestrained against movement away from contact with the inner surface of the fabric enclosure such that the membrane is movable to an aspiration position wherein the tongue is spaced from the inner surface of the fabric enclosure, and the membrane is alternatively movable to a venting position wherein internal pressure causes the membrane to extend outwardly through the vent;
• wherein a first distance from the distal end of the tongue to a closest end of the vent is shorter than a second distance from the distal end of the tongue to a closest end of fastening between the periphery of the membrane and the fabric enclosure.