2024 No Microbiological and chemical quality of indoor air in kindergartens in Slovenia https://pubmed.ncbi.nlm.nih.gov/30734572/ Rejc, T. Europe Observational Elementary (K-5) Carbon Dioxide (CO2) Bacteria Fungi Air quality Kindergartens Microorganisms Black carbon Carbon dioxide (CO2) Seasonal monitoring in two kindergartens found high CO₂ levels and airborne microorganisms, especially in spring and winter. CO₂ exceeded 1000 ppm in 89% of samples, supporting improved ventilation and reduced classroom density. 2019