A gas distributor distributes a gas across a surface of a substrate processing chamber. The gas distributor has a hub, a baffle extending radially outward from the hub, a first set of vanes and a second set of vanes. In one version, the hub has a gas inlet and a gas outlet. The baffle has an opposing first and second surfaces. First vanes are on the first surface of the baffle and direct gas across chamber surfaces. In one version, the first vanes comprise arcuate plates that curve and taper outward from the hub. Second vanes are on the second surface of the baffle and direct gas across the second surface of the baffle. In one version, a gas feed-through tube in the hub can allow a gas to bypass the first and second set of vanes.