The diploma thesis is focused on the impact of fuels and ventilation for selected smoke characteristics at internal fires. The aim of the thesis was to recapitulate basic physical and chemical smoke characteristics in the theoretical part based on literary research. We described the impact of ventilation and fuel properties on smoke characteristics at internal fires. In the experimental part of the diploma thesis, we designed our own calculation procedure for the selected smoke parameters using the Microsoft Excel spreadsheet. It is easy instalation specific values that can easily calculate the resulting value before prepared formula in the program. This calculation procedure can serve not only for teaching but also practical use. This calculation procedure can be used for pedagogical purposes but also in practice.