Abstract
Optical instruments are very often used on populations of particles and on single particles because of the very fast, or real-time, response. Nevertheless, the response depends on optical size and properties that are not the parameters of interest. In industrial and environmental hygiene, the aerodynamic size, above approximately 0.5 μm, is generally the ruling parameter; it may therefore be of interest to calibrate the optical signal in terms of aerodynamic size distributions.
In this work several light-scattering portable instruments have been operated as area monitors, connected with a data acquisition system and a personal computer to build an accurate statistical trend of the signal and averages. A PERSPEC (personal spectrometer) was also run to draw ambient air through the light-scattering cell and sample the same aerosol as the one generating the light-scattering signal, with the cell aperture becoming the system inlet, which is fairly close to an “inhalable” aperture. The PERSPEC collects the “inhalable” fraction on a filter with aerodynamic size separation; the filter can be cut and the extrathoracic, thoracic, and respirable fractions can be assessed. In addition, the tracheobronchial fraction is available as the difference between the thoracic and the respirable fractions. As long as the material and operations are not changed, it can be assumed that the aerosol in each position remains constant; therefore, the light-scattering signal can be correlated with the size distribution properties as measured by the PERSPEC samplers. In this way, the light-scattering instrument can be interpreted in terms of concentrations of single fractions or combinations of fractions. If more detailed information is sought, a much higher resolution in the aerodynamic selection and in the light-scattering channel is possible. Prodi, V.; Belosi, F.; Agostini, S.; Bettazzi, G.: Aerodynamic Calibration of Optical Instruments. Appl. Occup. Environ. Hyg. 8(4):356-359; 1993.