Disclosed is a method for treating a gas stream rich in hydrogen sulfide by providing one or more feed gas streams rich in hydrogen sulfide into a Claus reaction furnace, providing air into the Claus reaction furnace, providing supplemental oxygen into the Claus reaction furnace, and providing steam to the Claus reaction furnace, where the steam is in addition to any steam that may be present in gases that are recycled to the Claus reaction furnace. The components are then reacted at a temperature above about 2400.degree. F. and at a pressure sufficient to cause hydrogen sulfide to be converted into sulfur.