Introduction. Liquefied hydrocarbon gases (LHG) are widely used in various fields. The main components of LHG are: propane, isobutane and n-butane, which are not only combustible, but also explosive gases capable of detonation combustion. The detection of LHG in the air is a very urgent task in expert studies. To determine the component composition of various flammable liquids, for the purpose of their identification, chromatographs equipped with a capillary quartz column with a phase that allows detecting saturated hydrocarbons of the homologous series from pentane to pentatetracontane inclusive are used in the Forensic Expertise Institutions of Federal Fire Service of EMERCOM of Russia. However, it is not possible to analyze the component composition of lighter hydrocarbons according to the previously proposed and used in expert practice method for detecting and studying flammable liquids/high liquids under these conditions. To solve the problem of unification of the use of the instrumental base for the detection of residues of flammable liquids, liquid liquids and light hydrocarbons, new chromatography conditions were selected using the existing equipment set. Goals and objectives. The aim of the study is to select the analysis conditions for detecting the remains of liquefied hydrocarbon gases after explosions of steam-air mixtures on the basis of the instrumental gas chromatographic complex in service with the Forensic Expertise Institutions of Federal Fire Service of EMERCOM of Russia. Research methods. To detect and determine the composition of residues of combustible components during explosions of vapor-gas-air mixtures, a hardware-software instrumental complex based on a gas-liquid chromatograph equipped with a flame ionization detector, a ZB-50 capillary column, and an attachment from a two-stage thermal desorber was used. Results and its discussion. In the course of the study, the optimal conditions for conducting gas chromatographic analysis were defined and selected in order to detect liquefied hydrocarbon gases. Recommended pressures are given for various carrier gases. It is shown that, by varying the pressure and inlet temperature, light hydrocarbons propane, butane, isobutane is fairly well separated on a gas-liquid chromatograph with a flame ionization detector and on a ZB-50 capillary column 30 meters long. Conclusion. The research shows that the problem of combining a hardware-software instrumental complex based on a gas chromatograph with an attachment from a two-stage thermal desorber used for the analysis of two groups of substances (liquefied hydrocarbons and flammable liquids, gas liquids) is solved by varying the pressure and temperature of the input. Keywords: gas-liquid chromatography, thermal desorption, liquefied petroleum gases, light hydrocarbons, air-fuel mixtures, vapor-gas-air mixtures, explosion, fire examination.

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