This study examined the influence of multiple factors—particularly occupant presence and air purifier operation—on indoor PM2.5 concentrations across 104 households in the Seoul metropolitan area. Both indoor and outdoor PM2.5 concentrations were continuously monitored and integrated with time-specific survey data to analyze spatial and temporal patterns of indoor exposure. Results showed that occupant presence significantly elevated indoor PM2.5 concentrations, especially during periods of high activity (08:00~15:00 and 18:00~20:00). The indoor/outdoor (I/ O) concentration ratio was also significantly higher during these periods, indicating that occupant activities were a major contributor to indoor PM2.5 concentrations. Air purifier use was found to be associated with a consistent reduction in indoor PM2.5 concentrations, regardless of occupancy status. Notably, the I/O ratio also decreased when air purifiers were in operation, demonstrating their effectiveness in controlling both indoor emissions and the infiltration of outdoor pollutants. These findings provide empirical evidence of the multifactorial dynamics governing indoor PM2.5 exposure and highlight the importance of occupant-centered and time-specific strategies for effective residential air quality management.

Abstract
1. 서 론
2. 연구 방법
    2.1 주택 실내·외 공기질 모니터링
    2.2 설문조사
    2.3 자료의 전처리 및 분석 방법
    2.4 통계분석
3. 결 과
    3.1 주택 실내 PM2.5 농도 분포
    3.2 주택 실내 PM2.5 농도와 실외 PM2.5 농도 간관계
    3.3 공기청정기 가동 여부에 따른 주택 실내 PM2.5농도 분포 특성
4. 고 찰
5. 결 론
감사의 글
References

• 박신영(서경대학교 환경화학공학과) | Shin-Young Park (Department of Environmental Chemical Engineering, Seokyeong University)
• 장혁(서경대학교 환경화학공학과) | Hyeok Jang (Department of Environmental Chemical Engineering, Seokyeong University)
• 권중보(서경대학교 환경화학공학과) | Jung-Bo Kwon (Department of Environmental Chemical Engineering, Seokyeong University)
• 이철민(서경대학교 환경화학공학과) | Cheol-Min Lee (Department of Environmental Chemical Engineering, Seokyeong University) Corresponding author