A smog chamber arrangement is presented for the study of aerosol forming photoreactions and is tested by first determinations of aerosol residence times. The automatic monitor for sulphuric acid and sulphate of the TU Berlin has been used for sensitive measurements of sulphuric acid and other particulate sulphur aerosols under the condition of a smog chamber. The formation of both compounds is observed in irradiation experiments with the biogenic hydrocarbon alpha-pinene in a NOx photosmog in the presence of SO2. The sulphur balance is dependent on the photochemical conditions, and 10 to 30% of the sulphur have been recovered. Since there are no inorganic cations present further characterization of the particulate sulphur is necessary.