Finding F-1541

“After the first reopening, we observed a significant decrease, of 18.5%, in daily average indoor CO2 levels and a 22.4% decrease in daily peak CO2 levels, when compared with pre-COVID levels.”

Eichholtz The effect of post-COVID-19 ventilation measures on indoor air quality in primary schools… (2024). PNAS nexus. Page 2. CKB 5771

Structure

Factor: Carbon dioxide (CO₂)
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 18.5
Caveat: the reopening changed occupancy and window use at once, so the two cannot be separated

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.