Method and device for detecting a leakage in the area of at least one cooling device of a furnace and a furnace

A method for detecting a coolant leakage in an area of at least one cooling device of a furnace, said at least one cooling device containing a liquid coolant, the method comprising:

• introducing liquid coolant from a furnace cooling device into a furnace chamber of the furnace;
• continuously removing a stream of exhaust gas from the furnace chamber over a period of time Z, the removal comprising the following steps:
• dividing off a partial exhaust gas stream from the stream of exhaust gas during a period of time Z;
• condensing vaporous constituents contained in the partial exhaust gas stream and determining a stream of condensate thus obtained;
• comparing the stream of condensate obtained with a condensate-stream limit value and
• indicating a coolant leakage from the furnace cooling device into a furnace chamber of the furnace if the stream of condensate exceeds the condensate-stream limit value.