Comparative analysis of indoor volatile organic compound levels in an office: Impact of occupancy and centrally controlled ventilation

Understanding the effects of human occupancy and ventilation on indoor air quality, especially in the presence of volatile organic compounds (VOCs), is crucial for human health. We investigated VOC concentrations in an office environment with varying occupancy and ventilation in real-time via proton transfer reaction time-of-flight mass spectrometry by evaluating conditions across different ventilation control scenarios. Among the 276 analyzed species, 113 VOCs were quantified, where 77.8% of the total emission rate is attributed to human occupancy, 12.9% to building sources, and 9.30% to supply air. The emissions rates of occupants and building were quantified by considering natural ventilation (Q = 117.36 m³ h⁻¹) in the emission source, which increased their emission rate by 31.5%. A decrease in the ventilation recirculation ratio (RR = 0.5) reduced the total concentration of indoor VOCs by 55.1% owing to the introduction of fresh ambient air. Notably, daytime measurements with the half-open damper of the ventilation system highlighted the importance of controlled ventilation in mitigating VOC presence. Our findings suggest that considering natural ventilation is important in assessing indoor air quality, that HVAC system management is crucial in enhancing indoor air quality, and that building design and operational strategies must be optimized for the health of indoor environments.