Apparatus, systems, and methods for processing workpieces are provided. In one example implementation, a hydrogen gas mixed with an inert gas can be reacted with an oxygen gas to oxidize a workpiece at atmospheric pressure. A chemical reaction of a hydrogen gas with an oxygen gas facilitated by a hot workpiece surface can positively affect an oxidation process. A reaction speed of the chemical reaction can be slowed down by mixing the hydrogen gas with an inert gas. Such mixture can effectively reduce a partial pressure of the hydrogen gas. As such, the oxidation process can be carried out at atmospheric pressure, thereby, in an atmospheric thermal processing chamber.