Abstract
Over 70% of a pupil’s school life is spent inside a classroom, and indoor air quality has a significant impact on students’ attendance and learning potential. Therefore, the indoor air quality in primary school buildings is highly important. This empirical study investigates the indoor air quality in four naturally ventilated schools in China, with a focus on four parameters: PM2.5, PM10, CO2, and temperature. The correlations between the indoor air quality and the ambient air pollution, building defects, and occupants’ activities have been identified and discussed. The results indicate that building defects and occupants’ activities have a significant impact on indoor air quality. Buildings with better air tightness have a relatively smaller ratio of indoor particulate matter (PM) concentrations to outdoor PM concentrations when unoccupied. During occupied periods, the indoor/outdoor (I/O) ratio could be larger than 1 due to internal students’ activities. The indoor air temperature in winter is mainly determined by occupants’ activities and the adiabatic ability of a building’s fabrics. CO2 can easily exceed 1000 ppm on average due to the closing of windows and doors to keep the inside air warmer in winter. It is concluded that improving air tightness might be a way of reducing outdoor air pollutants’ penetration in naturally ventilated school buildings. Mechanical ventilation with air purification could be also an option on severely polluted days.
Highlights
China has been experiencing serious air pollution problems in recent years, due to rapid industrialization, urbanization, and increasing energy consumption [1,2,3]
The average indoor PM2.5 and PM10 concentrations in occupied classrooms range from 199 μg/m3 to 149 μg/m3 and 205 μg/m3 to 138 μg/m3, respectively, which is 5 times higher than the requirements of the World Health Organization (WHO)’s and China’s standards
The highest level of indoor PM10 reached 267 μg/m3, which was found in School C, and the lowest reading of 80 μg/m3 was found in School A
Summary
China has been experiencing serious air pollution problems in recent years, due to rapid industrialization, urbanization, and increasing energy consumption [1,2,3]. It may not be safer to stay indoors, as some studies suggest that indoor air quality closely correlates to the outdoor pollution level, in urban and industrial areas [9]. Another important factor which affects indoor air quality is building defects. Riley et al [10] suggested that the penetration of particles through building cracks would significantly affect indoor air quality, especially for buildings where air exchange through openings or cracks is dominated by pressure differences arising from natural forces. Long et al [13] investigated nine homes in Boston and figured out that dusting, vigorous walking, and sautéing were the key factors affecting indoor air quality
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