A series of experiments was carried out in order to study whether various fire-fighting substances influenced the detection of traces of accelerants in samples taken from a fire scene. The experiments consisted in the following: piles made up of typical flat furnishing materials were set on fire by means of a specific flammable liquid and then extinguished by a defined fire-fighting agent. Samples recovered from the fire scene were then subjected to chromatographic analysis. The obtained results suggest that the application of extinguishing foam is linked to the introduction of substances into the samples which might be detected in the process of analysis. The presence of these compounds does not hinder the identification of the accelerant, provided the person conducting the analysis knows how to interpret the obtained results correctly.