Impact of door-opening events on air exchange rates in naturally ventilated spaces

We investigated the effect of unintentional door-opening events on air exchange rates (AERs) in naturally ventilated environments. Using occupant-generated carbon dioxide (CO₂) as a natural tracer gas, we performed experimental measurements in an office setting. We employed the mass-balance approach to estimate AER and CO₂ generation rates, focusing on the influence of intermittent door-opening events caused by occupant movement. We observed significant increases in AER during occupancy periods due to unintentional door opening. The AERs increased by 11.5 %, 15.6 %, 40.5 %, and 41.1 % for one, two, three, and four occupants, respectively. We found a strong positive correlation between the number of people entering or leaving per hour and AERs, indicating that occupant movement through hinged doors is the primary driver of air exchange. These results underscore the critical role of unintentional door-opening events in shaping natural ventilation performance and infiltration dynamics. We rigorously validated our estimation model using tests and independent datasets, which confirmed its high predictive accuracy in compliance with ASTM D5157 standards. Our findings have practical implications for the optimization of demand-controlled ventilation and variable air volume systems. By incorporating dynamic occupancy patterns, these systems can increase energy efficiency while maintaining optimal indoor air quality.