A scanning mobility particle sizer

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The formation of secondary organic aerosols is a major source of particulate matter (such as smog) in the atmosphere. Secondary organic aerosols are generated by the oxidation of volatile organic compounds and can affect visibility, climate, and human and ecological health. We have recently constructed a photoreaction chamber ("smog chamber") to simulate atmospheric conditions and to study the reactions that lead to aerosol formation. A unique feature of our instrument is the availability of a mid-infrared semiconductor laser based trace gas sensing system. This sensor allows us to monitor the concentrations of reactants, for example, BTEX compounds (benzene, toluene, ethylbenzene, xylene) in real time. We have also succeeded in detecting product species during the ultra-violet light induced oxidation reactions.