Embodiments of process chambers are provided herein. In some embodiments, a process chamber includes: a chamber wall defining an inner volume within the process chamber; a substrate support disposed in the inner volume having a support surface to support a substrate, wherein the inner volume includes a processing volume disposed above the support surface and a non-processing volume disposed at least partially below the support surface; a gas supply plenum fluidly coupled to the processing volume via a gas supply channel disposed above the support surface; a pumping plenum fluidly coupled to the processing volume via an exhaust channel disposed above the support surface; and a sealing apparatus configured to fluidly isolate the processing volume from the non-processing volume when the substrate support is in a processing position, wherein the processing volume and the non-processing volume are fluidly coupled when the substrate support is in a non-processing position.