Provided are gas distribution apparatus with a delivery channel having an inlet end, an outlet end and a plurality of apertures spaced along the length. The inlet end is connectable to an inlet gas source and the outlet end is connectible with a vacuum source. Also provided are gas distribution apparatus with spiral delivery channels, intertwined spiral delivery channels, splitting delivery channels, merging delivery channels and shaped delivery channels in which an inlet end and outlet end are configured for rapid exchange of gas within the delivery channels.