Assessing Indoor Air Quality in a Chicago Sports Center Using Low-Cost Sensors

Abstract Indoor air quality (IAQ) is a critical public health concern, especially in sports facilities where high occupancy and physical activity increase exposure risks. This study assessed IAQ in a Chicago sports center using low-cost Air Quality Egg sensors, deployed in the basketball courts, rock-climbing area, and weight room from 14 March to 2 April 2024, followed by a colocation test to ensure sensor consistency. Results showed PM 2.5 concentrations across all locations remained below the World Health Organization’s 24-h guideline of 15 µg m −3 but demonstrated distinct diurnal patterns associated with occupancy levels. Indoor PM 2.5 was positively associated with CO 2 and relative humidity (RH), while temperature effects varied by location. Multiple regression models using CO 2 , RH, and temperature explained 34% of PM 2.5 variability, with CO 2 being the strongest predictor. Infiltration analysis showed weak correlations ( R 2 = 0.04) between indoor and outdoor PM 2.5 , indicating that indoor sources were dominant and the building was relatively well sealed. The estimated infiltration coefficients ranged from 0.07 to 0.12, and indoor-generated PM 2.5 levels (1.11–1.66 µg m⁻ 3 ) were relatively lower than those reported in similar buildings. Among the three locations, the weight room recorded the highest levels of PM 2.5 , CO 2 , and RH during both peak and evening hours, despite having the highest air exchange rate based on CO 2 decay analysis. The findings suggest that enhanced ventilation may still be needed to improve IAQ in the weight room. This study demonstrates the utility of low-cost sensors in capturing spatial and temporal IAQ variability. The results emphasize the importance of aligning ventilation strategies with space usage in recreational environments. Graphical Abstract