B100 and B20 were found to contain various fatty acid methyl esters (FAMEs) that could be observed and identified by using a typical fire debris column and gas chromatography/mass spectrometry (GC-MS) temperature program. The extraction of B100 and B20 from fire debris using passive headspace concentration is not optimal because of its reduced efficiency in extracting heavier components and the phenomena of competitive adsorption; however, a subsequent solvent wash with pentane of a sample suspected of containing biodiesel allows for the detection and identification of FAMEs present in burned substrates. The study found that E85 was readily extracted from debris by using passive headspace concentration, and it was easily recognized with the use of a fire debris GC-MS method configured to detect light oxygenated compounds. Upon evaporation of E85, the ethanol remains the primary component in the total ion chromatogram (TIC), while the gasoline evaporates in the expected manner. In addition, the mode of extinguishment has a substantial influence on the retention of ethanol in a fire debris sample and may impact the analyst’s ability to determine the presence of an E85 fuel used as an ignitable liquid. Water has a detrimental effect on the presence of ethanol in E85 samples in fire debris. Typical fire-debris instrumental conditions were used to analyze the samples. 2 tables, 7 figures, and 12 references