The aim of the bachelor thesis was to examine the issue of non-linear spread of fire indoors. The work is mainly focused on the factors of the development of internal fire and its causes. The thesis also describes various scenarios of internal fires that can occur under certain conditions. It is divided into 6 chapters, while the first chapter is focused on the characteristics of the course and parameters of the internal fire. In the second chapter we focused on the possibility of modelling the Backdraft phenomenon itself. The practical part of this bachelor thesis contains an experimental test of a fire in a scale model of a house, where we simulated the occurrence of Backdraft. In this part of the work there is a detailed process of modelling the Backdraft phenomenon- a description of the construction of a scale model of the house, the conditions necessary for the occurrence of this phenomenon, or the presence of individual combustible materials. The thesis also contains photo documentation, for a better idea of the experiment. In conclusion, we focused on the tactics of conducting the intervention in the event of an internal fire.