An air bag includes a wall defining an interior in which a gas is received to inflate the air bag, and at least one vent opening through the wall and a vent valve carried by the wall. The vent valve has at least one valve opening, and the vent valve is moveable between a first position where the valve opening is aligned with at least one vent opening and a second position where the valve opening is at least partially misaligned with at least one vent opening to at least partially close the vent opening. The vent valve is in its first position until deployment of the air bag beyond a threshold which moves the vent valve to its second position.