Let science speak for itself – Reflection on the invisibility
of a problem with indoor air quality in schools – Part 1
Let science speak for itself – we highly recommend 'Report from the 2nd European Conference on Indoor Air Quality: French Schools'. It is a cohesive and detailed reflection on indoor air quality in schools that also includes a broader European initiative. In the first part, let's talk about the invisible problem of air in schools that has health and cognitive impacts. And in the second part, ventilation in schools is not only a technology problem but also an implementation problem, this due to systemic barriers and challenges.
The invisible problem – Children spend between 10 and 15% of their lives in classrooms. Yet, nearly anybody thinks about the air in schools. This problem is real – but still invisible.
"Prevention is the blind spot of public health policies." – Antoine Flahault, Director of the Institute of Global Health, University of Geneva
- People spend approximately 80% of their time indoors, and children spend between 10 and 15% of their lives in classrooms.
- In France, at least 40% of classrooms suffer from inadequate ventilation, according to data from Public Health France, ANSES, and CSTB.
- Attention must be given to the negative impact of stale air on students' academic performance.
“At school, we think our children are protected. But ultimately, there are a lot of pollutants.” – Isabella Annesi-Maesano, Research Director at Inserm, IHU Immun4Cure
"Proper air renewal could reduce nearly 30,000 cases of asthma in children each year." – Guillaume Boulanger, Head of the Quality of Living and Working Environments and Population Health Unit, Public Health France
- Children are particularly vulnerable due to the immaturity of their immune and respiratory systems, as well as the incomplete development of the blood-brain barrier.
- The issue is multifaceted, health-related (asthma, wheezing, developmental disorders), cognitive (learning disrupted by heat and confinement), and economic. Indoor air pollution in homes is estimated to cost around €19 billion annually and is associated with nearly 20,000 deaths each year.
- Schools must become centres of health education. There is a need to strengthen data collection, regulations, and monitoring of indoor air quality, which are currently far less developed than those for outdoor air.
"No prevention is done, so contamination continues." – Céline Grassien & Isabelle Leibl, AprèsJ20-AssoCle on observations and expectations of families
"Illness is the leading cause of school absences in OECD countries, and this trend is increasing sharply." – Elisa Zeno, Head of the Forgotten Schools and Families collective
- Indoor air quality in schools has become a major concern for parents, given its impact on children's health, cognitive performance, learning, and overall well-being.
- The pandemic highlighted the importance of indoor air quality indicators, such as CO2 concentration, with a recommended maximum threshold of 800 ppm in school spaces, including classrooms, dormitories, cafeterias, and gymnasiums. However, field measurements have shown that this threshold is often significantly exceeded, sometimes by factors of 2, 3, or even more.
- Alarming data from OECD countries, such as Ireland, where 60% of school absences were illness-related, with a 46% increase in sick leave between 2022 and 2023. In France, secondary school students lost an average of 7 to 9% of teaching time in 2022-2023, compared with 5% in 2013-2014. This situation is particularly concerning, as it affects 12 million students and over one million staff members who are exposed to potentially contaminated air for 5 to 10 hours every day.
"No one would tolerate unsafe drinking water in schools, yet we inhale nearly 1,000 times more air each day than we drink water." – Elisa Zeno, Head of the 'Forgotten Schools and Families' collective
"Children are getting infected at school. This has been said over and over again, we know it." – Michaël Rochoy, General practitioner, University of Lille
- In 2023, 41% of schools had at least one classroom exceeding 1,700 ppm of CO₂, well above the recommended threshold of 800 ppm. Poorly renewed air promotes the onset of sick building syndrome at levels as low as 1,000 ppm, leading to irritation, fatigue, reduced concentration, cognitive impairment, and increased school absences. Public Health France estimated that 30,000 cases of asthma could be prevented among children aged 6 to 11 through improved indoor air quality.
- There is a need to highlight the health, educational and economic implications: a 10% reduction in respiratory infections would free up the equivalent of 600 general practitioners' workload.
More information about the conference
On June 20th, 2025, the 2nd European Conference on Indoor Air Quality: French Schools was jointly organised by a collective of seven organisations: the Geneva Health Forum (GHF), the Institute for Global Health (ISG), the Centre for Studies and Expertise on Risks, Environment, Mobility and Planning (Cerema), the Ecoles et familles oubliés (EFO) Collective, the Molinari Economic Institute, the Nous aérons Collective and the Scientific and Technical Centre for Building (CSTB).
