Author(s)

SUBHAJIT BISWAS, CHRISTINA VANDERWEL

Abstract

This study presents a comparative analysis of indoor and outdoor air pollution in residential homes in urban, semi-urban and rural environments. High-resolution airborne particulate matter (PM) concentration measurements were collected between January 2023 and October 2025 from multiple residential locations in Hampshire, UK. The results demonstrate that while seasonal trends for indoor and outdoor PM often appear similar at monthly averages, the temporal variations of the unaveraged data reveal that indoor environments experience short term periods of particularly high concentrations, linked to occupant behaviour and indoor activities like cooking and wood burning. The probability distributions clearly indicate that indoor spaces maintain a higher baseline concentration compared to the outdoor environment. Diurnal analysis shows that indoor air is most polluted during the evening (16:00 to 22:00), with the mean indoor-to-outdoor ratio (I/O) peaking at ≈1.2–1.3, implying that indoor air is on average 20–30% more polluted than outdoor air. During these periods, in specific households, occupant behaviour can drive I/O levels to ≈2, implying the indoor pollution level being over 100% higher than outdoor conditions. These findings underscore the sensitivity of indoor air quality to lifestyle choices and suggests targeted interventions to reduce indoor pollutant accumulation.

Keywords

indoor/outdoor air pollution monitoring, air pollution sources, built environments, public perceptions/engagement, occupant behaviour, ventilation, particulate matter, seasonal variations