This diploma thesis deals with the evaluation of chimney bodies and the detection of causes of fire. In the case of fire protection it's most important to find out possible cause of the fire and consequently to avoid fire influence. The thesis describes the legislation of the Slovak Republic in the area of detecting the causes of fires. It also describes the technical conditions and requirements for fire safety in the installation and operation of fuel appliances. As well as the conditions for the construction of central heating, chimneys, flue gas ducts and the periods of their cleaning and inspection. The statistics in the diploma thesis points to the most frequent percentages of fires from the point of view of chimney sweeps as well as financial damages caused by these fires in the territory of the Slovak Republic in the last 10 years. In the thesis there are described individual legislative bases, procedures for measurements of chimney sweepers and appliances, analytical methods, collection and registration of samples and their subsequent examination.