Diploma thesis mediates view of the use of infrared inspections in detecting hidden danger of fire as a tool for discovering hidden fire hazard in practice firefihters. The aim of this thesis is to demonstrate the importance of thermal imaging cameras in practice firefighters. The thesis is divided into four chapters. In the first chapter we explained the rise and spread of fire. The second chapter is devoted to the various laws applicable to thermal imaging diagnostics, the principle of operation of the thermal imager and introduces us to its versatility in practice. The third chapter introduces us using the thermal imager in the Fire and Rescue Service of the Slovak Republic. The fourth chapter describes the objectives of the thesis. In the fifth chapter we thermovision camera practical measurements verify the acquired knowledge to simulated fire. Finally, we evaluated the measurement.