Air bag vent with tether

An apparatus for helping to protect an occupant of a vehicle includes an inflatable vehicle occupant protection device that is inflatable to an inflated condition for helping to protect the vehicle occupant. The protection device includes a panel of material that helps define an inflatable volume of the protection device. The panel includes a vent opening that has an open condition for venting inflation fluid from the inflatable volume. The vent opening is in the open condition during initial deployment of the protection device. A channel encircles the vent opening. The channel is at least partially defined by a peripheral portion of the panel that extends along a periphery of the vent opening. A tether has a portion that extends through the channel. The tether draws together the peripheral portion of the panel to reduce the size of the vent opening when the protection device deploys a predetermined distance toward the inflated condition.