Finding F-1542

“For example, after the first reopening, we observed a significant decrease of 29.1% in average indoor CO2 levels in NV classrooms, and 15.2% (29.1–13.9%) in MV classrooms.”

Eichholtz The effect of post-COVID-19 ventilation measures on indoor air quality in primary schools… (2024). PNAS nexus. Page 3. CKB 5771

Structure

Factor: Carbon dioxide (CO₂)
Intervention: Natural ventilation
Setting: classroom
Study design: measurement study of school classrooms before the pandemic and after the two reopenings: carbon dioxide and fine particles logged in naturally and in mechanically ventilated classrooms and compared across the periods (class 4)
Effect: difference 29.1
Caveat: the reopening changed occupancy and window use at once

A Finding records what one published document states, verbatim and with its page. It is not a conclusion of Coridum; see the Claims that build on it.