Analysis of Indoor Air Quality and Occupant Perception Under Different Mechanical Ventilation Operational Modes in a University Amphitheater

This paper presents an analysis of indoor air quality (IAQ) and occupant perception under different mechanical ventilation operational modes in a university amphitheater. Indoor environmental parameters, including air temperature, relative humidity, indoor air velocity, and CO2 concentration, were measured in accordance with ISO 7726. Ventilation performance and outdoor air supply requirements were evaluated according to BAS EN 16798-1 and ASHRAE 62.1, while thermal comfort interpretation followed ISO 7730. In parallel, a questionnaire survey was conducted to assess occupants’ perceptions of indoor air quality and its influence on concentration under different ventilation operating conditions. The results showed that CO2 concentrations occasionally exceeded 1000 ppm during extended occupancy periods but remained below 800 ppm for more than 60% of the measurement time. According to BAS EN 16798-1, the indoor environment was predominantly classified as Category I based on the indoor–outdoor CO2 concentration difference. Survey responses indicated that most students perceived the indoor air as clean, while 67% reported that IAQ influenced their ability to concentrate. The findings highlight the importance of occupancy-related ventilation control strategies in large educational spaces and demonstrate the potential for balancing indoor air quality and energy efficiency through appropriate ventilation system operation. The presented methodology may support future development of data-driven approaches for optimizing mechanical ventilation performance in university buildings.