A method and apparatus for supplying a gas mixture to a load lock chamber is described. In one embodiment, the apparatus supplies a gas mixture to a pair of process chambers, comprising a first ozone generator to provide a first gas mixture to a first process chamber, a second ozone generator to provide a second gas mixture to a second process chamber, a first gas source coupled to the first ozone generator via a first mass flow controller and a first gas line, and coupled to the second ozone generator via a second mass flow controller and a second gas line, and a second gas source coupled to the first ozone generator via a third mass flow controller and a third gas line and coupled to the second ozone generator via fourth mass flow controller and a fourth gas line.