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Sulphuric acid, H2SO4, has been identified to play major role in atmospheric new particleformation and in subsequent particle growth. The oxidation of sulfur dioxide (SO2) tosulfur trioxide (SO3) initiated by the reaction with the hydroxyl radicals (OH) isassumed to be the dominant formation pathway of sulfuric acid (H2SO4) in thetroposphere. It has been suggested in the recent years that the reactions of CriegeeIntermediates (CIs) with SO2 may also contribute to the H2SO4 formation, althoughthe significance of this pathway compared to the reaction of OH with SO2 is stillunder discussion. As the ozonolysis of anthropogenic and biogenic terpenes emittedinto the atmosphere may represent an important source of OH and CIs a betterunderstanding of the ozonolysis mechanism in relation to the H2SO4 formation isrequired. In this study, we present the results obtained during the investigation of the ozonolysis ofseveral unsaturated volatile organic compounds, including tetramethylethylene, α-pinene andlimonene, using a newly constructed large atmospheric simulation chamber, HELIOS(ICARE-CNRS, Orléans, France). The HELIOS facility consists of a large outdoorsimulation chamber (volume of 90 m3) equipped with a wide range of in-situ on-line andoff-line analytical instrumentation (FTIR, PTR-TOF-MS, GC-MS, CIMS (OH and H2SO4),SMPS, Figaero-API-TOF-CIMS, HCHO monitor and others). The results of kinetic andmechanistic studies of the reactions of different CIs with SO2 induced by the ozonolysis ofthe studied VOCs under different conditions will be presented. The H2SO4 loss on the Teflonchamber wall and by the aerosol uptake were characterized using direct H2SO4 and particlemeasurements. Keywords: ozonolysis, Criegee Intermediate, sulfur dioxide, sulfuric acid, HELIOS [ABSTRACT FROM AUTHOR]