Occupant-driven ventilation and indoor exposure dynamics in naturally ventilated Ethiopian university dormitories

Naturally ventilated university dormitories are complex real-world exposure environments in which indoor air quality is strongly influenced by occupant behavior, high occupancy density, and limited ventilation control. Despite growing interest in the relationship between indoor environmental quality (IEQ) and sleep quality, evidence from high-occupancy dormitories in low-resource settings remains limited. This study investigated ventilation-related indoor exposures and subjective sleep quality in Ethiopian university dormitories and conducted an exploratory, uncontrolled pre-post assessment of a behavioral eco-feedback strategy to encourage healthier nighttime ventilation practices. Overnight monitoring of CO 2 , relative humidity, temperature, PM 2.5 , and PM 10 was conducted among 128 participants, together with subjective sleep assessment using the Groningen Sleep Quality Scale (GSQS). A self-selected subset of 41 male volunteers participated in a non-randomized, uncontrolled eco-feedback phase that included personalized feedback on monitored indoor parameters and ventilation recommendations, followed by post-feedback monitoring. Indoor conditions were frequently suboptimal, with elevated CO 2 concentrations (median 1435 ppm) and relative humidity (median 63%). Higher CO 2 and relative humidity levels were associated with higher GSQS scores, and the mixed-effects model identified CO 2 as the only statistically significant measured predictor of subjective sleep quality. In this context, CO 2 was interpreted as an indicator of ventilation adequacy, occupancy-related emissions, and the possible accumulation of occupant-generated bioeffluents, rather than as a direct causal agent affecting sleep. During the post-feedback phase, participants reporting continuous nighttime window opening showed lower CO 2 concentrations, relative humidity, and GSQS scores than at baseline, whereas no statistically significant pre-post differences were observed for particulate matter. These findings provide real-world evidence on the relationship between ventilation-related exposures, occupant-driven ventilation behavior, and subjective sleep quality in high-density dormitory environments.