Method for detecting at least one property of an intumescent paint , with which a structural part of a building structure is coated, wherein the method comprises the following steps a) providing a device for detecting at least one property of an intumescent paint , with which a structural part of a building structure is coated, wherein the device comprises: - at least one housing , wherein the housing has at least one test opening , which is designed to separate a test area , coated with the intumescent paint , on the structural part of the building structure from other regions of the structural part ; - at least one heat source , wherein the heat source is arranged inside the housing and wherein the heat source is designed to supply thermal energy to the test area ; and - at least one sensor , wherein the sensor is designed to detect a change in a property of the intumescent paint that is induced by the thermal energy; b) fastening the device onto the structural part of the building structure in such a way that the test opening of the housing separates a test area , coated with the intumescent paint , on the structural part of the building structure from other regions of the structural part ; c) supplying thermal energy at the test area by means of the heat source ; and d) detecting at least one change in a property of the intumescent paint , induced by the thermal energy, by means of the sensor . a) providing a device for detecting at least one property of an intumescent paint , with which a structural part of a building structure is coated, wherein the device comprises: - at least one housing , wherein the housing has at least one test opening , which is designed to separate a test area , coated with the intumescent paint , on the structural part of the building structure from other regions of the structural part ; - at least one heat source , wherein the heat source is arranged inside the housing and wherein the heat source is designed to supply thermal energy to the test area ; and - at least one sensor , wherein the sensor is designed to detect a change in a property of the intumescent paint that is induced by the thermal energy; - at least one housing , wherein the housing has at least one test opening , which is designed to separate a test area , coated with the intumescent paint , on the structural part of the building structure from other regions of the structural part ; - at least one heat source , wherein the heat source is arranged inside the housing and wherein the heat source is designed to supply thermal energy to the test area ; and - at least one sensor , wherein the sensor is designed to detect a change in a property of the intumescent paint that is induced by the thermal energy; b) fastening the device onto the structural part of the building structure in such a way that the test opening of the housing separates a test area , coated with the intumescent paint , on the structural part of the building structure from other regions of the structural part ; c) supplying thermal energy at the test area by means of the heat source ; and d) detecting at least one change in a property of the intumescent paint , induced by the thermal energy, by means of the sensor . <EOS>