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A variety of tools are used to simulate atmospheric aging, including smogchambers and flow reactors. Traditional, large-scale smog chambers ageemissions over the course of hours to days, whereas flow reactors rapidlyage emissions using high oxidant concentrations to reach higher degrees ofoxygenation than typically attained in smog chamber experiments. Theatmospheric relevance of the products generated under such rapid oxidationwarrants further study. However, no previously published studies havecompared the yields and chemical composition of products generated in flowreactors and smog chambers from the same starting mixture.  The yields and composition of the organic aerosol formed from thephoto-oxidation of α-pinene and of wood-combustion emissions in asmog chamber (SC) and two flow reactors: a potential aerosol mass reactor(PAM) and a micro-smog chamber (MSC), were determined using aerosol massspectrometry. Reactants were sampled from the SC and aged in the MSC and the PAMusing a range of hydroxyl radical (OH) concentrations and thenphoto-chemically aged in the SC.  The chemical composition, as well as the maximum yields and emissionfactors, of the products in both the α-pinene and wood-combustionsystems determined with the PAM and the SC agreed reasonably well. High OHexposures have been shown previously to lower yields by breakingcarbon–carbon bonds and forming higher volatility species, which residelargely in the gas phase; however, fragmentation in the PAM was notobserved. The yields determined using the PAM for the α-pinenesystem were slightly lower than in the SC, possibly from increased walllosses of gas phase  species due to the higher surface area to volume ratiosin the PAM, even when offset with better isolation of the sampled flow fromthe walls. The α-pinene SOA results for the MSC were not directlycomparable, as particles were smaller than the optimal AMS transmissionrange. The higher supersaturation in the flow reactors resulted in morenucleation than in the SC. For the wood-combustion system, emission factorsmeasured from the MSC were typically lower than those measured from the SC.Lower emission factors in the MSC may have been due to considerablenucleation mode particles formed in the MSC which were not detected by theAMS or due to condensational loss of gases to the walls inside or after theMSC. More comprehensive coverage of the potential particle size range isneeded in future SOA measurements to improve our understanding of thedifferences in yields when comparing the MSC to the SC. The PAM and the SCagreed within measurement uncertainties in terms of yields andcomposition for the systems and conditions studied here and this agreementsupports the continued use of the PAM to study atmospheric aging

Inter-comparison of laboratory smog chamber and flow reactor systems on organic aerosol yield and composition