A 100,000-franc indoor climate study commissioned by the Zurich cantonal parliament has revealed widespread excessive heat and high carbon dioxide levels across regional schools, alongside logistical failures that included widespread sensor thefts and equipment sabotage. The 37-page report details how 19 out of 20 tested vocational and secondary schools recorded indoor temperatures exceeding 30 degrees Celsius during monitoring periods spanning 2024 and 2025.
Classroom Temperature and Carbon Dioxide Extremes
The investigation deployed specialized sensors in top-floor and south-facing classrooms across 20 institutions to monitor thermal conditions and air quality. Researchers recorded a peak temperature of 34.1 degrees Celsius at the Technische Berufsschule Zürich. The highest CO2 reading reached 3,594 ppm at the Kantonsschule Zürcher Oberland, vastly exceeding the standard indoor ceiling where levels above 1,400 ppm are categorized as unacceptable for prolonged learning environments.
Duration of exposure varied significantly depending on building infrastructure. At the Kantonsschule Wiedikon, CO2 levels remained above 1,400 ppm for 283 cumulative hours. Conversely, the Berufsschule für Detailhandel und Pharmazie, which utilizes a mechanical ventilation system, exceeded that threshold for only a single lesson hour, though records note its system frequently circulated warm external air.
Operational Hurdles, Sabotage, and Equipment Thefts
Efforts to test remediation measures across eight control schools encountered severe operational disruptions. In April 2025, inspections revealed that 90 percent of the deployed CO2 monitoring units—designed to signal air quality changes via four-color LED lights—had been stolen from classrooms. Additional devices suffered from battery tampering or intentional removal of sensors. Mobile cooling units provided to classrooms drew heavy criticism from teachers and students over operational noise levels. An occupant at the Kantonsschule Zürcher Unterland in Bülach reported that the machinery was extremely loud and induced colds, while the Berufsfachschule Winterthur noted that fan noise severely disrupted classroom presentations and discussions.
Political Friction and Prior Findings
The study itself emerged from a contentious political debate within the cantonal parliament. Right-of-centre parties, including the SVP and FDP, opposed commissioning the analysis in 2023, arguing that its conclusions regarding basic ventilation practices would merely validate common sense. Following the release of the findings, parliamentary critics reiterated that the insights offered little novelty compared to federal initiatives. The Federal Office of Public Health conducted similar indoor air quality measurements across three cantons between 2013 and 2015, while federal pilot projects examined heat resilience in schools as early as 2022.