Transport of cyclic volatile methylsiloxanes in residence due to the use of personal care products

Emissions of cyclic volatile methylsiloxanes (cVMS) due to the use of personal care products pose adverse effect on indoor air quality. We make the first attempt to explore the emission characteristics of decamethylcyclopentasiloxane (D5, the most abundant cVMS) in an occupied residence via modelling and experimental approaches. A mass transfer model for characterizing the emissions of D5 from human skin lipids is developed, which incorporates the adsorption/desorption effect of D5 onto indoor surfaces that was ignored previously. A long-term field campaign in residence was conducted to examine the D5 emission behaviors, showing a number of concentration peaks after using personal care products. Special enhanced-ventilation and emission experiments were designed to determine the mass transfer parameters in the model via a hybrid optimization method, which were then used to predict D5 concentrations in some other test days. Good agreement between model predictions and observations demonstrates the effectiveness of the model and measured parameters. Feature importance analysis on indoor D5 transport is further performed, indicating that air exchange rate is the most important factor compared with temperature and relative humidity. This study comprehensively uncovers the transport dynamics of D5 in realistic indoor settings, which is helpful for human-related source characterization and control.