The article focuses on analysis of application features of means for thermal monitoring for diagnostics of electric contacts overheating. Analysis results are systematized for identifying signs of such a fire-prone process as occurrence of large contact intermediate resistances. It is proved the possibility of application of overheating indicators based on thermo-bimetallic sensitive elements. Thermo-bimetallic indicators are used for the detection of defective electrical contacts during holding preventive measures dedicated to electric service.