A simulation study of the changes in PM2.5 concentrations due to interzonal airflow variations caused by internal door opening patterns

Short-term variations in interzonal airflows can cause significant fluctuations in gaseous or particulate matter concentrations in indoor environments and therefore, interzonal airflow variations need careful consideration when modelling indoor pollutant concentrations. This study investigates the potential accuracy of modelling interzonal airflow variations and assesses the effect of interzonal airflow variations on indoor pollutant concentrations. A variable interzonal airflow is compared with a time-weighted average interzonal airflow, and the differences in the resulting estimates of indoor pollutant concentrations are analysed. Interzonal airflow variations were simulated by the opening/closing of internal doors for periods of 1, 2, 5, 10, 15 and 30 min. Based on experimental comparison, it can be concluded that the modelling approach used, accurately predicts PM2.5 concentrations for interzonal airflow variations for durations of 10 min or greater, with increasing accuracy for longer durations. The simulations demonstrate that both the time of occurrence and duration of the interzonal airflow variations are critical in determining indoor concentrations, and indicating that a time-weighted average interzonal airflow is not a suitable substitute for modelling interzonal airflow variations, as it under-predicts mean PM2.5 concentrations by up to 28%.