Urban air pollution involves complex mixtures of gases and particulate matter whose molecular-level composition and gas-particle partitioning remain poorly characterized, limiting our understanding of secondary organic aerosol (SOA) formation. We address this gap using controlled atmospheric simulations combined with detailed molecular characterization.</p> <p>Two distinct urban atmospheric scenarios were simulated in the CESAM smog chamber: a standard urban (traffic emissions and biogenic precursors) and a biomass burning enhanced. Both scenarios were aged under controlled irradiation with NOx to simulate tropospheric photochemistry.</p> <p>PM<sub>1</sub> concentrations reached 15 ± 7 µg.m<sup>-3</sup> for the standard scenario and 63 ± 24 µg.m<sup>-3</sup> for the biomass burning scenario, with organic aerosol fractions of approximately 17 % and 40 %, respectively. Gas-phase analysis via proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF-MS) identified 23 volatile organic compounds (VOCs), dominated by oxygenated species (74–77 %). Particle-phase molecular analysis using ultrahigh-performance liquid chromatography electrospray ionization ion mobility quadrupole time-of-flight mass spectrometry (UPLC/ESI-IMS-QTOFMS) revealed 32 distinct compounds. The biomass burning scenario showed elevated source-specific tracers, including a levoglucosan isomer, nitrophenolic compounds (e.g., 3-methyl-4-nitrocatechol, 4-nitroguaiacol), and oxidized aromatics. Volatility distributions estimated via group contribution methods placed most compounds in the semi-volatile, low-volatility, and extremely low-volatility organic compound ranges (C* < 300 µg m<sup>-3</sup>), indicating substantial functionalization and partitioning.</p> <p>These results demonstrate the capacity of simulation chambers to generate reproducible urban aerosol analogues with distinct source-specific molecular signatures and well-characterized volatility distributions. This detailed molecular speciation provides a robust basis for process-oriented model evaluation and opens perspectives for systematic investigations of SOA formation pathways under controlled urban photochemical conditions.