Estimation of the infiltration factor of particulate matter using indoor and outdoor measurements
Loading...
Date
2026-06-15
Authors
Πηλού, Θεοδώρα
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The present MSc thesis focuses on the estimation of the infiltration factor of particulate matter ΡΜ2.5 in indoor environments, using simultaneous indoor and outdoor concentration measurements.
Chapter 1 presents the general characteristics of particulate matter, including its classification according to particle size and emission source. Emphasis is placed on its impacts on both climate and human health.
The infiltration factor, Finf, is a key parameter for understanding the relationship between outdoor air pollution and indoor exposure, as it expresses the fraction of outdoor particles that penetrates and remains in the indoor environment, as discussed in Chapter 2.
For the estimation of Finf, different methodological approaches were applied, which are described in detail in Chapter 3. Initially, ordinary least squares linear regression was used, where the slope of the relationship between indoor and outdoor concentrations was considered as an estimate of the infiltration factor. In addition, the LOWESS method was applied in order to investigate the non-linear relationship between the indoor-to-outdoor concentration ratio and the outdoor ΡΜ2.5 concentration. This approach enabled the estimation of Finf mainly under conditions of elevated outdoor pollution, where the influence of indoor sources is relatively lower. Furthermore, Bayesian regression was applied with the aim of providing a probabilistic estimation of the infiltration factor and a more complete representation of the uncertainty associated with the results. At the same time, the effect of different time lags was examined, in order to account for the response time of indoor concentrations to variations in outdoor pollution.
In the context of this thesis, ΡΜ2.5 data from different environments were analyzed, including school classrooms, hospital areas, university buildings and areas affected by industrial or urban pollution, as described in Chapter 4. The measurements were conducted using low-cost sensors and ΡΜ2.5 monitoring instruments, while the data were subjected to time alignment and quality control.
The analysis presented in Chapter 5 revealed important differences in Finf among the examined indoor environments. In some cases, indoor concentrations closely followed the variations of outdoor pollution, while in other spaces an increased contribution of indoor-generated particles was observed. The seasonal analysis also showed that building operation conditions can significantly affect the penetration and accumulation of particles in indoor environments.
In Chapter 6, in addition to the infiltration factor, the contribution of indoor sources, Cig, to the total indoor ΡΜ2.5 concentrations was calculated. This calculation allowed the separation of indoor pollution into a component originating from the outdoor environment and a component associated with indoor activities or ventilation conditions.
Finally, in Chapter 7, a statistical analysis of high ΡΜ2.5pollution events was performed, aiming to investigate the response of indoor environments during periods of elevated outdoor concentrations.
Overall, this thesis contributes to a better understanding of the relationship between outdoor and indoor air pollution and highlights the importance of estimating the infiltration factor for the assessment of actual human exposure to ΡΜ2.5.
Description
Keywords
Infiltration factors, Particulate matter