An air bag (12) is inflatable by inflation fluid. A support member (20) has a first vent opening (44) for enabling flow of inflation fluid away from the bag (12).
A vent member (46) is movable relative to the first vent opening (44) between a first condition in which the vent member does not close the opening that enables flow of inflation fluid away from the bag (12) and a second condition in which the vent member at least partially blocks the flow of inflation fluid through the opening and away from the bag. A tether (50) has a first portion (52) connected for movement with the bag (12) as the bag is deployed. The tether (50) is associated with the vent member (46) and causes it to move relative to the opening (44) from the first condition to the second condition as the bag (12) is deployed.