Journal of Kones. Combustion Engines, VoIB, No 1-2, 2001 COMPARISON OF EMISSION RATES OF MONOCYCLIC AROMATIC HYDROCARBONS IN EXHAUST GASES FROM SELECTED TYPES OF CARS DURING THE NEDC DRIVING TEST Magdalena UK, Jan KONIECZYNSKI Silesian Technical University, Department of Air Protection, Akademicka 2,44-100 Gliwice, Poland Phone: +48322371290, Fax: +48322371290, e-mail: magzak@polsl.gliwice.pl KnysztofKLEJNOWSKI Institute ofEnvironmental Engineering of the Polish Academy of Science MiCune-Skiodawskiej 34,41-819 Zabrze, Poland Phone: +48322716481, Fax: +48322717470, e-mail: klej@ipis.zabrze.pl Piotr BIELACZYC BOSMAL Automotive Research and Development Centre Sarni Stok 93, 43-300 Bielsko-Biala, Poland; Phone: +48338130598, Fax: +4833813560, e-mail: piotr.bielaczyc@bosmal.com.pl Abstract. An increase in unleaded gasoline consumption causes growth of enussion of monocyclic aromatic hydrocarbons (MAlIs) such as benzene and its a1ky1ated derivatives: toluene, ethylbenzene, isopropylbezene, and trimethylbenzenes (TMB). These compounds are highly toxic in both, direct and indirect effects on living organisms. This paper describes the applied method of measurements and presents results of a study on benzene and its homologues in car exhaust, obtained during driving test performed on a chassis dynamometer at Emission Testing Laboratory at the BOSMAL Automotive Research and Development Centre in Bielsko - Boo. Examples of some MAHs emission factors are reported. Effects of the use of a catalytic converter (TWC) and temperature conditioning of cars on MAHs emissions from examined vehicles were assessed. Results of determination of MAHs content in various types of gasolines and in diesel fuel arealsopresented. 1. Introduction A growing number of motor vehicles enhancesthe problem of air pollution and confirms a convictionthat the traffic is a great environmental problemto big cities. The atmospheric air contamination with organic compounds emitted by cars has become a subject of growing social concern in recent years. This concern results from changes in hitherto existing perception of the vehicularemissionsas emissions of inorganic substances. Monocyclic aromatic hydrocarbons, such as benzene and its alkylderivatives: toluene, m-, p-, o-xylenes, ethylbenzene, isopropylbezene, 1,2,4- and 1,3,5-trimethylbenzene, are of a special significance among all organic compounds. These hydrocarbons belong to the group of volatile organic compounds (VOCs). The term "volatile organic compounds" is attributed to all these aromatic compounds which can form photochemical ozone in presence of nitrogen oxides and solar energy [1]. A comparison of profiles of MAHs concentration in car exhaus and in the ambient air in a vicinity of roads indicates motor vehicles as the main source of these pollutants in the neighbourhood of communication arteries [2]. 348