Abstract: An endothermic-base type heat treating furnace atmosphere is produced in an external generator by a partial oxidation between air and alcohol (e.g. ethanol). An alcohol-rich mixture is prepared and reacted at an elevated temperature to form a product gas comprising carbon monoxide, nitrogen, hydrogen, carbon dioxide, methane and water. The product gas is quickly cooled and any water that condenses is removed. The generator product gas is then introduced into a furnace within which it usually undergoes further reaction to provide a suitable nonoxidizing heat treating atmosphere. In one aspect of this invention, the generator gas is used for carburizing ferrous metal workpieces without additional increase of the carbon potential.