Abstract: The invention concerns a process for detecting water leaks in smelting furnaces (2; 4) or in metal or alloy treatment plants, comprising the following steps: (i) providing at least one smelting furnace (2; 4), or at least one metal or alloy treatment plant provided with a water cooling system (5) and being connected to a process fume exhaust system; (ii) mixing in the cooling water a tracer chemical which is volatile in the event of water leakage together with the exhaust gases and which is suitable to be detected by an analysis system of the exhaust gases; and (iii) detecting said tracer chemical contained in the exhaust gases by said analysis system comprised in said process fume exhaust plant, wherein said tracer chemical is deuterated water. The invention further refers to a Plant for the production of metals or alloys.