In the second pandemic winter, schools in Germany remain open, despite high infection figures. Students are crowded into classrooms, protected only by FFP2 masks and regular testing, because the vaccination rate among children is still low. How high is the risk of infection in classrooms, and how well can simple ventilation help reduce it? Journalists from the Süddeutsche Zeitung (SZ) measured the infection risk in classrooms, daycare centers and at family gatherings using CO₂ measuring devices. In charts and graphics, they illustrate how quickly the aerosol concentration rises and how only consistently opened windows can reduce the risk of infection.
The project is a visually narrated paid article and was very well received by SZ subscribers. Many non-subscribers also clicked on the article, which is why it also led to new conversions.
The analysis of the CO₂ values of the different scenarios is based on measurements that the Süddeutsche Zeitung carried out with two different CO₂ traffic light models. They differ in design, but both have the same sensor installed. The SZ was provided with one model free of charge by the company ISIS IC. Measurements were also taken with a self-built CO₂ traffic light following instructions from the Umwelt Campus Birkenfeld. In addition, we received data donations from the Michaeli-Gymnasium in Munich. Students Simon, Felix and Samuel from the high school measured carbon dioxide concentrations in various classrooms as part of a “Jugend forscht” project and won the special “Thinking Safety” prize.
The CO₂ limit at 1000 parts per million (ppm) is based on assessments by the German Federal Environment Agency. Here, 1000 ppm of carbon dioxide in the room air is considered harmless and a room air with 1000 ppm to 2000 ppm of carbon dioxide is considered alarming.
To calculate the probability of having an infected child in a class, we assume that twice as many children are infected as officially known. Although regular rapid tests can detect some infected children, they cannot detect all, especially since children more often show few symptoms of illness and rapid tests have limited accuracy. The probability of infecting more children is based on an interactive calculator from the Max Planck Institute for Chemistry. In the scenarios presented, we assumed a classroom with one teacher and 25 students, 50 percent of whom are vaccinated or recovered, and who spend 25 hours together in a room over the course of a week.
What was the hardest part of this project?
To obtain the data, the journalists performed several measurements themselves over a period of one year and evaluated them together with data donations from schools and interpreted them with the support of experts. The Data team worked together with colleagues from the visual desk and science editorial team, which required cross-departmental planning, to present readers with a cleanly researched and well-visualized story. The evaluation underpins the current debate on mandatory vaccinations, student vaccinations and school closures with easy-to-understand scientific insights and offers guidance on safer indoor meetings through proper ventilation.
What can others learn from this project?
This project shows how sensors can be used in a meaningful way to add scientific insight and data to a debate currently taking place in society. The story takes the reader through an everyday problem – worrying about children at school during a pandemic – but also shows why the risk of infection in a room rises quickly, even in small groups, and how this can be reduced quite significantly by proper ventilation. It also shows the great potential of collaborations between multiple departments and teams even within the same media house, because projects like these are made possible through working together.