2018 Yes https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6068750/#:~:text=The%20analysis%20of%20the%20questionnaire,perceived%20IAQ%20was%20not%20observed. Vornanen-Winqvist, Camilla Europe Experimental Teachers Students Ventilation Hybrid ventilation Indoor air quality Mycobiota Indoor air questionnaire School buildings Trichoderma citrinoviride A significant change in indoor mycobiota was found; the dominant, opportunistic human pathogenic species Trichoderma citrinoviride found in settled dust in the classroom before the improvement was nolonger detected. In addition, the concentrations of CO2, TVOC, and some single VOCs, especially toluene and decamethylcyclopentasiloxane, decreased. The analysis of the questionnaire results indicated that the perceptions of unpleasant odors and stuffy air decreased, although a statistically significant improvement in perceived IAQ was not observed