We have studied the possibility of continuous particulate monitoring, by an optical system, on the filters of a two-stage streaker sampler. The streaker deposits, collected for PIXE analysis, have been examined off-line by measuring the attenuation of a light beam. The optical analysis provides, in a few minutes, an estimate of hourly total mass concentrations, over a one week period, for both stages, very useful as a selection for further PIXE irradiation. We describe the set-up and the calibration procedures, where PIXE plays a fundamental role in resolving different aerosol compositions and in validating the prototype performance. The results obtained over 2 weeks of operation and the comparison with the aerosol component determined via PIXE analysis, are also discussed.