Curtain air bag including inflatable perimeter gas channel

This application relates to air bag assemblies for use in protection of vehicle passengers during a collision event and more particularly to a curtain air bag assembly adapted for rapid inflated deployment away from a storage position for coverage across an extended region between an occupant and a side portion of a vehicle interior. An air bag restraint system for a transportation vehicle. The restraint system includes an inflatable curtain having a gas inlet, an upper edge, a lower edge and a perimeter. A gas emitting inflator is in fluid communication with the gas inlet. The inflatable curtain includes an inflatable flow channel in fluid communication with the gas inlet. The inflatable flow channel extends at least partially around the inflatable curtain in a path such that at least a potion of the inflation gas is communicated through the inflatable flow channel and along the lower edge.