Quantitative assessment of the effect of surface deposition and coagulation on the dynamics of submicrometer particles indoors

Abstract

Exposure to airborne particles indoors depends on particle concentration, which is affected by air filtration, ventilation, and particle dynamics. The aim of this work was quantitative assessment of the effects of coagulation, surface deposition, and ventilation on the submicrometer particle concentration indoors. The assessment was obtained from measured particle loss rate and deposition velocity parameters. The experiments were conducted in an experimental chamber for three different types of aerosols: environmental tobacco smoke, petrol smoke, and ambient air aerosols. Particle number concentration and size distribution were measured in the size range between 0.017 and 0.898 μm by SMPS. The average values for the overall deposition loss rates varied from 4.3 × 10-5 s-1 (0.16 h-1) to 1.1 × 10-4 s-1 (0.39 h-1). The overall deposition velocities associated with surface deposition and coagulation ranged from 9.6 × 10-4 cm s-1 to 2.4 × 10-3 cm s-1, and for surface deposition only from 2.8 × 10-4 cm s-1 to 6.3 × 10-4 cm s-1. For indoor conditions with an air exchange rate above 1.3 h-1, (natural ventilation, no filters) only a reduction in particle number of about 20% is attributed to the surface deposition and coagulation.