Occupants' exposure to nitrogen dioxide (NO2) in European school and kindergarten buildings - A review

Heidi Salonen*, Tunga Salthammer, Lidia Morawska

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review


The aim of this study was to summarize the extent of occupants' exposure to nitrogen dioxide (NO2) in European school and kindergarten buildings. Google Scholar and PubMed were used to search the literature. The calculated median, as well as the mean, concentrations of NO2 in school (median 20.8 µg/m3; mean 26.1 µg/m3) and kindergarten (median 17.2 µg/m3; mean 35.5 µg/m3) buildings were found to be below the World Health Organization (WHO)'s guideline of 40 µg/m3 for the annual mean NO2 concentration. However, mean O2 concentrations in many studies were over 40 µg/m3, indicating situations where the WHO guideline is exceeded. Outdoor levels of NO2 are a reliable predictor of indoor NO2 levels across seasons, with median Indoor/Outdoor (I/O) ratios of 0.7 and 0.8 in school and kindergarten environments, respectively. These findings support the importance of mitigation measures to reduce ambient NO2 levels, and to prevent high levels of NO2 exposure in school and kindergarten buildings.

Original languageEnglish
Title of host publication16th Conference of the International Society of Indoor Air Quality and Climate
Subtitle of host publicationCreative and Smart Solutions for Better Built Environments, Indoor Air 2020
PublisherInternational Society for Indoor Air Quality and Climate (ISIAQ)
ISBN (Electronic)9781713823605
Publication statusPublished - 2020
MoE publication typeA4 Conference publication
EventIndoor Air - Seoul, Korea, Republic of
Duration: 1 Nov 20205 Nov 2020
Conference number: 16


ConferenceIndoor Air
Country/TerritoryKorea, Republic of
Internet address


  • Indoor air
  • Indoor/Outdoor ratio
  • Kindergartens
  • Nitrogen dioxide (NO2)
  • School buildings


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