2016 No https://pubmed.ncbi.nlm.nih.gov/27258661/ Salthammer, T Africa Asia Australia Europe North America South America Observational Epidemiology Study Students Elementary (K-5) Middle/Jr High (6-8) High School (9-12) Ventilation rates Temperature Carbon Dioxide (CO2) Carbon Monoxide (CO) Particulate Matter (PM) Volatile Organic Compounds (VOCs) Thermal comfort Ventilation Carbon dioxide (CO2) Indoor chemistry Exposure in classroom Guideline values High carbon dioxide concentrations in classrooms, which indicate poor ventilation conditions, and the increasing particle matter in urban outdoor air have, in particular, been identified as primary causes of poor indoor air quality in schools. Despite this, the conditions in most schools continue to be in need of improvement. There are many reasons for this. In some cases, the local administrative bodies do not have the budgets required to address such concerns, in other cases regulations and laws stand in contradiction to the demands for better indoor air quality, and sometimes the problems are simply ignored.