Products of petroleum refining classified as flammable liquids, are often misused deliberately as accelerants to start intentional fires. Gasoline is the most widely used accelerant in arson cases among petroleum distillates. The aim of diploma thesis was to follow influence of weathering in gasoline samples and to monitor the factors of temperature and time as quantities that affect it. The work use data from experiments of other authors who dealt with the weathering of gasoline at different temperatures and on different materials. In some cases accelerant was prepared artificially as a simplified version of the original gasoline sample. The influence of temperature (25 °C to 600 °C), used material whereon petrol was applied on (synthetic and natural fabrics) and the determination time of accelerant (0 to 4 hours) was observed. Analysis of the samples by GC-MS showed, that toluene and lower alkylbenzenes are the most volatile components of gasoline and subject to weathering at room temperature. On the other hand, less volatile compounds, such as higher alkylbenzenes and naphthalenes, can be detected up to 200 °C. In polyester and wool samples, gasoline residues was not detected two hours after their combustion. The fast arrival of fire investigators or use of portable analytical detectors by the intervening units may prevent the accelerator samples from being degraded by the process of weathering.