Enhancing Indoor Air Quality and Minimizing Airborne Virus Dispersion Under Various Ventilation Strategies While Maintaining Thermal Comfort

Abstract

Indoor air quality (IAQ) and thermal comfort are critical factors that influence occupant health, productivity, and general well-being in office environments. The COVID-19 pandemic has further highlighted the importance of effective ventilation strategies in mitigating the transmission of airborne viruses. This research investigates the performance of three ventilation strategies: indoor recirculation systems (4-way ceiling cassette air conditioners), natural ventilation, and mixed mode ventilation (AC + natural ventilation) in maintaining optimal IAQ, thermal comfort, and infection control in an open-plan office setting. Using a combination of computational fluid dynamics (CFD) simulations and real-world environmental monitoring, this study evaluates airflow patterns, pollutant dispersion, and thermal regulation under different ventilation conditions. This thesis explicitly demonstrates that IAQ, thermal comfort, and airborne virus transmission are deeply interconnected. Poor air quality not only impairs comfort and productivity but also prolongs aerosol suspension time, elevating infection risk. As such, ventilation strategies must be designed to address these three aspects holistically. The findings reveal that the air conditioning (AC) system, while providing controlled air distribution, often leads to stagnation zones that reduce air mixing efficiency and increase pollutant accumulation. Natural ventilation, though beneficial under favourable conditions, exhibits inconsistent performance due to external weather variations, leading to excessive humidity fluctuations and temperature instability. In contrast, mixed mode ventilation emerges as the most effective strategy, offering improved airflow uniformity, improved pollutant dilution, and greater adaptability to seasonal changes. The results demonstrate that a well-optimised hybrid system, which strategically combines an AC system and natural ventilation, can mitigate the limitations of standalone approaches by balancing fresh air intake, controlled temperature regulation, and efficient humidity management. This research contributes to a novel integrated methodological framework that bridges CFD simulations with IoT-based environmental monitoring, ensuring robust validation of ventilation performance under real-world conditions. The findings have significant implications for the optimisation of heating, ventilation and air conditioning (HVAC) and public health policies, particularly in the post-pandemic era, where IAQ is a major concern. By addressing critical knowledge gaps in ventilation performance, this thesis provides practical recommendations for facility managers, architects, and policy makers to develop more resilient and health-conscious indoor environments.