[Specific surface factor of dust particles and preliminary selection of silica dusts]

The results of particles analysis of three kinds of silica dust by means of miscroscopy and sedimentation in Andreasen's pipette served as a base for the determination of factor phi specific for particle surface. This factor is expressed as a ratio of the mean projected diameter (dp) to the aerodynamic diameter (d). The formula of the factor is: (formula: see text). The value of factor phi for tested silica dusts ranges from 2.0 to 2.6 (mean value--2.3), while the variability coefficient is 13.5%. Taking into account the value of factor phi determined by experiment and the value of dispersion of silica dust particles, the expected permeability of the selector (elutriator) and the deposition of dust in lungs were calculated.