Comparison of the air change per hour measured over four seasons in the residential buildings of the urban, rural, and industrial areas of South Korea: K-IOP Study

Abstract

Air infiltration, calcuated by air changes per hour (ACH) is a key factor in assessing the potential amount of air borne pollutants moving from outdoor into indoor spaces. We measured the natural ACH through fall, winter, spring, and summer (2 weeks/season), in 81 nonsmoking elderly houses located in urban (n = 29), industrial (n = 26) and rural (n = 26) areas from 2021 to 2022 consecutively. Indoor CO2 data measured at dawn (01:00 to 05:00 a.m.) over four season was used to estimate the ACH. Moreover, morning ACHs were also calculated from the CO2 level monitored in the morning, when the levels were dropped significantly with opening a window during fall, winter, and spring. The ACH at dawn over the four seasons ranged from 0.02 to 0.03,while that in the morning with opening a window was 0.2 to 0.3. Our multivariate regression models demonstrated that the difference in CO2 concentration during dawn was positively associated with the ACH change after adjusting for seasonality. In addition, after controlling for the study area, ACH was approximately 50 % higher during summer than during the other seasons (p < 0.05). This study elucidates the seasonal and regional distributions of ACH; a determination of these patterns may further contribute to future simulation or prediction studies assessing the associations among indoor air quality, activity patterns and ventilation practices among Korean elderly population.