Mass Balance Model for Estimating Indoor and Outdoor Contributions to Residential PM2.5 and Indoor-Generated PM2.5 Composition Profile
YIXIANG WANG, James Schauer, Marilyn Black, Michael Bergin, Junfeng Zhang, Linchen He, College of Health, Lehigh University
Abstract Number: 494
Working Group: Indoor Aerosols
Abstract
As individuals spend the majority of their time indoors, indoor air pollution—particularly fine particulate matter (PM2.5)—plays a substantial role in overall personal exposure. Indoor PM2.5 originates from both outdoor infiltration and indoor activities, and distinguishing their respective contributions is critical for effective exposure mitigation and air quality management.
We conducted a field study in 43 residences in Shanghai, where 48-hour PM2.5 samples were collected simultaneously indoors (bedrooms) and outdoors under two controlled conditions. In the "True Filtration" scenario, a portable air purifier equipped with coarse, HEPA, and activated carbon filters was used. In the "Sham Filtration" scenario, the same device was fitted with only a coarse filter. To isolate infiltration from outdoor air, windows remained closed throughout both sampling periods.
Collected PM2.5 samples were analyzed for mass concentration and chemical composition, including organic matter (OM), elemental carbon, metals, and other trace elements. A mass balance model was applied to quantify indoor source contributions and derive the emission composition profile.
Results showed that indoor sources were responsible for 60±26% of total indoor PM2.5 under True Filtration and 63±17% under Sham Filtration. Organic matter was the predominant indoor-generated component, contributing 69% during Sham Filtration and rising to 92% during True Filtration. The OM fraction was remarkably consistent across households, with strong linearity observed in both filtration settings (R² = 0.97–0.98).
These findings demonstrate the model’s versatility across diverse indoor environments and highlight its potential to enhance our understanding of indoor PM2.5 exposure and source characteristics, providing a foundation for more targeted air quality interventions.