Fire debris analysis is a specialty of fire investigation and forensic sciences that is based on objective science and subjective evaluation. Objective science is used in the analytical scheme until chromatographic or masschromatographic data are generated. Then comes the most diffi cult part of the analysis: the interpretation of the results. Even though many efforts have been made to render the interpretation of the data as objective as possible (standards are available, for example), the fi nal call whether an ignitable liquid is present or not, rests on the evaluation of the criminalist and remains subjective. Furthermore, it will probably continue to remain so forever. As such, the importance of the fi re debris analyst’s skills does not lie so much in his/her ability to operate a gas chromatograph-mass spectrometer, but rather in his/her capacity to determine if a set of peaks and valleys exhibited by a sample resembles closely enough those of a reference ignitable liquid. Although training in interpretation must heavily rely on practical exercises, the theoretical base must be obtained through the reading of scientifi c articles and books.