The investigations of the turbulence in the flow are one of the most expensive, thus the improvement of existing ones and the research related to the new methods are in continual development. The multidisciplinary approach led to the application of the infrared thermography in the turbulent boundary layer observations with the endpoint goal of energy and cost savings in its early stages. This work presents the use of the industrial type infrared thermography for identification of the turbulent zones in the free convective flow, so far the less investigated problem related to convection heat transfer. It was shown that the transient spot temperature difference, measured on the complex geometry of the real-scale coal ventilation mill, of the Thermal plant “Kostolac B”, by an infrared camera, is a good parameter for identification of the most influenced positions by turbulence. The defined fields with maximal transient temperature difference are in accordance with theory and values calculated by numerical simulations for clean geometry, confirming the assumptions. The described method is also convenient for use in cases when the other methods are not applicable because of the complex geometry, unapproachable, or for the other similar reasons. The results from this work would support the more precise measurements with the research type infrared camera, the other methods for measurements.