When a forest fire hits a mountainous area, the life of an overhead transmission line is affected by the heat, extinguishing water, chemicals, and dust. The life of a wire depends on the combination of these elements. Generally, how a conductor wire is affected by forest fire can be analyzed only when the forest fire is accurately modeled and its effects identified. In Korea, however, there are few studies that were conducted based on a forest fire model for transmission lines. There have not been any results from analyzing actual test specimens that were exposed to forest fire. In this study, an artificial dust experiment device was designed and used in the tests because the deterioration characteristics from a forest fire and dust cannot be directly analyzed. The device is set to show field conditions. ACSR 410 mm2 were used as test specimens. These wires are commonly used for overhead transmission lines in Korea and now are used to analyze tensile strength. In addition, the transmission line samples were collected from the field where a forest fire occurred. They were then compared with the experiment data to estimate their degree of deterioration.