A shaft furnace, in particular a blast furnace, includes a metal jacket defining the furnace outer wall and a protective layer protecting the inner surface of the outer wall. At least one condition monitoring probe is arranged inside within the protective layer to monitor the latter. The condition monitoring probe is connected to a wireless module arranged outside the outer wall to transmit condition monitoring data. The wireless module is located inside a casing mounted to the outer surface of the metal jacket. The condition monitoring probe includes one or more conductive loops positioned at predetermined depths below the front face of the cooling plate body, or of the refractory lining, so that wear of the body, resp. refractory, can be detected by a change of an electrical characteristic of the loop(s) due to abrasion.