Characterization of particulate matter in a multizonal residential apartment: transport, exposure, and mitigation†

Due to rapid urbanization and lifestyle changes, people in developing countries like India spend most of their time indoors, just like those in developed countries. Indoor air pollution (IAP) studies in urban built environments in India are yet to gain momentum. Studies conducted so far are restricted to reporting pollutant concentration, providing limited insights into pollutants' source, transport, and fate. Comprehensive studies are critical to assessing IAP severity and developing and deploying effective mitigation strategies in built environments. The present study includes spatio-temporal monitoring of particulate matter (PM) in a multizonal residential apartment using a network of low-cost air quality monitors and research-grade instruments to characterize emission sources, assess transport metrics, estimate spatial exposure, calculate I/O ratios, and assess efficacies of different mitigation measures. Sub-micron particles dominated number size distribution for cooking and incense. Operation of air conditioners (AC) led to faster transport of pollutants from the kitchen to the bedrooms. PM exposure in all zones relative to the kitchen had comparable (∼0.8–0.9) exposure during cooking. The average I/O ratios during cooking were elevated throughout the apartment, with the kitchen (10.1 ± 8.9) and bedrooms (7.2 ± 5.7 & 7.4 ± 5.9) being the highest and lowest, respectively. Natural ventilation through balcony doors led to an average exposure reduction of 74–86% in different zones. AC operation reduced cumulative exposure, which was further reduced upon affixing a filter sheet on the AC pre-filter. Among the mitigation measures assessed, the highest cumulative loss rate (2.3 ± 0.1 h⁻¹) was observed for the portable air cleaner with the default HEPA filter.