Assessing the feasibility of TiO₂ photocatalytic coatings to improve indoor air quality in interactive scaled lecture hall models

Amid growing concerns over indoor air pollution in Egyptian university buildings, particularly those located near industrial zones, this study evaluates the effectiveness of titanium dioxide (TiO₂)-based photocatalytic coatings in improving indoor air quality (IAQ) in lecture halls. A 10% water-based TiO₂ suspension was manually applied to interior finishing surfaces in three scaled interactive models simulating real university classrooms, with material specifications and coating parameters detailed in the methodology section. Photocatalytic activity was activated under controlled UV-LED illumination in an unoccupied experimental environment. Indoor air quality was assessed by monitoring PM₂.₅, PM₁₀, NO₂, formaldehyde (HCHO), total volatile organic compounds (TVOCs), and CO₂ during 8-hour measurement sessions conducted under controlled conditions with no external airflow. CO₂ concentrations were recorded solely as indicators of chamber stability and ventilation conditions and were not interpreted as pollutants affected by photocatalytic activity. Statistical analysis revealed substantial reductions in particulate matter concentrations, with PM₂.₅ decreasing by approximately 55–61% and PM₁₀ by 65–73% across the tested models. NO₂ concentrations decreased by up to 46%, while HCHO reductions ranged between 29% and 32%, depending on the interior finishing configuration. In contrast, TVOCs exhibited variable behaviour, including temporary increases under certain conditions, likely associated with residual material off-gassing and transient photocatalytic intermediate formation. These findings confirm the potential of TiO₂-based photocatalytic coatings to reduce key indoor air pollutants under short-term, controlled activation conditions. However, real-world IAQ performance is strongly influenced by factors such as human occupancy, particulate resuspension, and dynamic ventilation patterns, which were beyond the scope of the present experimental setup. Future research should therefore investigate long-term photocatalytic performance in fully occupied and naturally ventilated educational environments.