A study on the dynamics of particulate matter infiltration in buildings

Abstract

The increased health risks related to the exposure of particulate matter (PM) pollution are evident. Given that people spend around 90% of their time indoors, indoor exposure to particles of outdoor origin has become an important focus in recent years. Several studies have attempted to estimate the relative contribution of outdoor particulates in indoor environments. In this study, an unoccupied room was used to conduct indoor and outdoor continuous PM measurements. The air exchange rate (AER) of the room was also measured and was varied by opening the windows at different amounts. A simple modification in the experimental procedure was also implemented to determine the indoor deposition rates (k) at different PM size fractions. Different models were considered and their ability to estimate the indoor PM concentration from outdoor PM data was investigated. This study provides estimates of the Infiltration Factor and also indicates the best-performing model, for different PM size fractions given no indoor sources and under natural ventilation conditions in a local setting. All models considered performed better for finer fractions (PM1) and models assuming steady-state conditions performed better than more complex models employing a dynamic solution of the mass balance equation (MBE) however, such models have problems in low AER conditions. BC was not found to be a reliable infiltration surrogate of PM and the high variability of the AER both with regards to the wind speed and its direction was exposed.