2020 No https://onlinelibrary.wiley.com/doi/10.1111/ina.12684 Vallecillos, Laura Europe Observational Exposure Study Elementary (K-5) High School (9-12) Volatile Organic Compounds (VOCs) Air quality Indoor air Outdoor air Passive sampling Thermal desorption Gas chromatography Mass spectrometry Volatile organic compounds (VOCs) The monitoring results showed that ethanol and isopropyl alcohol were the most common compounds found in indoor environments, with cleaning products as the main emission source. The VOCs i-pentane and n-pentane were found at the highest concentrations in the three sampling sites set in the school's playground, and their concentrations were strictly related to combustion processes from automobile traffic