Investigation of the submicron particle budget in an unoccupied building

This study seeks to improve our understanding of the drivers controlling particle concentrations in unoccupied indoor environments, i.e. air exchange, infiltration of pollutants from outdoor, surface deposition, possible nucleation of new particles, and particle transformations. A mass balance analysis of indoor aerosols has been performed using time-resolved measurements of particle number concentrations and composition during two campaigns. The first measurement campaign has been carried out from summer 2016 to fall 2017 and consisted in characterizing some of the parameters mentioned above, using gas tracers and two optical counters (OPC; TSI 8220 AEROTRAK) over 6 particle size bins (from 0.3 to over 10.0 μm). A second intensive campaign has been conducted during the fall of 2017 and consisted in characterizing the size distribution and chemical composition of submicron aerosols and its precursors, using state-of-the-art instrumentation such as HR-ToF-AMS and PTR-ToFMS for continuous measurements of both indoor and outdoor concentrations. We will first discuss the main parameters driving the indoor aerosol budget and we will provide insights into potential indoor sources or transformations by comparing indoor to outdoor particles.