Performance of innovative wall paints for CO2 reduction in classrooms: lessons from real-world applications

Purpose This study aims to assess the real-world effectiveness of commercially available CO2-absorbing paints in improving indoor air quality in educational buildings. By evaluating their performance under normal classroom conditions, the research examines whether these materials can meaningfully influence indoor CO2 concentrations and thus contribute to healthier and more comfortable learning environments. Design/methodology/approach The study monitored five commercially available CO2-absorbing paints applied to classroom walls in a school in Palma (Spain). Continuous measurements of CO2 concentration, temperature and relative humidity were collected over two consecutive academic years. Initial small-scale panel tests were followed by larger wall-scale application of the most promising paint. Comparative analyses, including weekly interannual evaluations, were used to quantify the paints' performance under real operating conditions. Findings Some paints were associated with localized differences in CO2 concentrations, with levels up to 53.4% lower at specific monitoring points during the panel testing phase. However, when the best-performing product was applied on larger wall surfaces, similar reductions were not consistently observed (in several rooms, mean CO2 levels even increased by up to 11%). Weekly interannual comparisons generally showed variations within ±10%, with occasional peaks above 1000 ppm, reflecting the strong influence of classroom occupancy patterns and ventilation behavior. Overall, the results indicate that classrooms where these paints were applied did not consistently exhibit lower indoor CO2 concentrations during the monitoring period. Originality/value This research provides one of the first long-term, real-world evaluations of commercially available CO2-absorbing paints in occupied classrooms. By combining continuous monitoring with multi-year analysis, it highlights the gap between laboratory claims and real operational performance. The findings provide practical evidence that such coatings should be considered, at best, complementary measures rather than standalone solutions for improving indoor air quality in educational environments.