Using low-cost sensors to investigate relationships between indoor and outdoor PM 2.5 during the COVID-19 lockdown period in urban areas of Bien Hoa city, Vietnam

Abstract

PM 2.5 pollution remains a pressing environmental concern in Bien Hoa city, a key industrial center within Vietnam’s Southern Key Economic Zone. This research utilized low-cost sensors to measure indoor and outdoor PM 2.5 levels in five urban households from April 2021 to January 2022, with calibration performed using the DustTrak™ II Aerosol Monitor 8530. During the COVID-19 lockdown, daily average PM 2.5 concentrations ranged from 22 to 40 μg/m³, meeting Vietnam’s air quality standards but exceeding the World Health Organization’s guidelines. Indoor PM 2.5 levels were significantly elevated in older homes due to factors such as smoking and incense burning, while outdoor levels were primarily impacted by traffic and other local sources, with peaks observed during rush hours. Seasonal analysis revealed reduced PM 2.5 concentrations during the rainy season, underscoring the mitigating effects of rainfall and natural ventilation on indoor air pollution. The significant linear correlation between indoor and outdoor PM 2.5 concentrations underscores the need for thorough air quality evaluations. This study is the first to assess indoor-outdoor PM 2.5 relationships in Bien Hoa City households using low-cost sensors over nearly a year, including the COVID-19 control period. The study demonstrates that low-cost sensors are an effective and practical option for air quality monitoring in resource-limited settings like Vietnam.