Three different compositions of polymer composite materials have determined percolation critical parameters and volatile organic compound (VOC) sensing abilities and it affecting factors are investigated in doctoral thesis. In all composite compositions ethylene vinyl acetate copolymer is used as matrix material. In first composition carbon black nanoparticles are used, but in second – short multiwalled carbon nanotubes. In third composition both previously mentioned nanoparticels were used. From all three elaborated compositions for further investigation was applied composite with highest sensing abilities. Also, there is investigated various fuel vapour sensing effect and fuel contents analysed in order to explain sensing effect. Researched if adding extra toluene and benzene influence sensing abilities. In literature review is investigated VOC and its dangerousness, how it is possible to detect VOC and what privileges polymer composites have. Likewise, it is reviewed about polymer composite sensing effect theoretical aspects and reviewed commercially available VOC and fuel vapour detectors. Doctoral thesis is written in Latvian language it contains 100 pages, 65 figures, 8 tables, 151 references and 3 annexes.