Finding F-1543

“We find that the trend of fine particle pollutants after reopening is like that of CO2, i.e. a significant overall decrease (13.9% for the first reopening and 18.9% for the second re opening, compared with the pre-COVID level), and the decrease of pol lutants for classrooms with natural ventilation is larger than that for classrooms with mechanical ventilation.”

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: Particulate matter (PM₂.₅ and PM₁₀)
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 13.9
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.