This diploma thesis deals with the process of monitoring flow and extent of a fire, which was generated inside of electrical appliance by using a thermal imaging camera. The theoretical part of this document includes an overview of heat transfer methods and puts emphasize on heat transfer, classification of thermal imaging systems and an overview of possibilities to apply thermography in practice. The practical part contains a description of the measured object and the description of the hot-air heater inside which the fire was caused due to the induced technical failure. The temperature of the surface was measured by using a thermal imaging camera. Furthermore, the observation of the experiment was recorded with a digital camera. In the heating coil area, the maximum temperature reached 572.7 ° C. Moreover, the highest temperature at the surface of the plastic cover reached 127 ° C.