The Air Students Breathe

The quality of indoor air directly affects the quality of learning

Indoor air quality (IAQ) is one of the most influential yet overlooked factors affecting educational environments. While schools invest heavily in teachers, technology, curriculum development, and learning facilities, the quality of the air students breathe often receives far less attention.

Research from across Europe demonstrates that poor indoor air quality is widespread in educational buildings. A 2024 systematic review covering 125 studies and 2,444 classrooms found that 81% of classrooms exceeded the recommended indoor CO₂ concentration of 1,000 ppm.[1] Elevated CO₂ is a reliable indicator of inadequate ventilation: when CO₂ is high, concentrations of airborne pollutants, allergens, particulate matter, and biological contaminants are typically elevated alongside it.

The implications extend beyond comfort. Poor indoor air quality has been linked to reduced concentration, increased fatigue, impaired decision-making, lower cognitive performance, and increased absenteeism. This white paper examines the state of indoor air quality in European schools, explores the impact of elevated CO₂ on health and learning outcomes, and presents evidence-based strategies – including fabric duct solutions – for creating healthier educational environments.

The Invisible Factor in Educational Success

Across Europe, more than 90 million students attend pre-primary, primary, and secondary schools. Every school day, they spend six to eight hours inside classrooms – expected to concentrate, solve problems, absorb information, collaborate, and perform academically.

Educational success is influenced by many factors: teaching quality, curriculum design, technology, and student engagement. Yet one factor often remains largely invisible – the quality of the air students breathe. Unlike inadequate lighting or excessive noise, poor air quality cannot easily be seen, heard, or felt until its effects are already measurable. As Swegon Air Academy member Petra Vladykova has noted, this remains a real – but still invisible – problem.

Why Indoor Air Quality Matters

Improving classroom air quality benefits the entire educational community – students, teachers, and the institutions responsible for both.

Understanding Indoor Air Quality in Schools

Indoor air quality is determined by multiple interacting factors, each affecting occupant health and comfort. The three primary categories are CO₂ concentration, temperature and humidity, and airborne pollutants – including PM₂.₅, PM₁₀, VOCs, and biological contaminants.

Why CO₂ is the key indicator

CO₂ is widely used as the primary indicator of ventilation effectiveness in occupied spaces. At the concentrations commonly found in classrooms – typically 1,000 to 3,000 ppm – CO₂ itself is not the direct cause of harm. Rather, elevated CO₂ is a reliable signal that ventilation is inadequate and that the broader indoor environment is deteriorating: allergens, fine particulates, VOCs, and biological contaminants accumulate alongside it.

This distinction matters. Improving ventilation to reduce CO₂ simultaneously addresses the full spectrum of indoor air contaminants. CO₂ monitoring is therefore the most practical and cost-effective tool for managing overall classroom air quality.

The European Air Quality Challenge

A growing body of research demonstrates that poor indoor air quality is widespread throughout European schools. The most comprehensive review to date analysed 125 studies covering 2,444 classrooms. The median CO₂ concentration was 1,487 ppm – nearly 50% above the recommended limit – with 81% of classrooms exceeding 1,000 ppm.

Lithuania: A Representative Northern European Example

Lithuania provides one of the most thoroughly documented national case studies of school air quality in Central and Eastern Europe. In 2018, the Lithuanian Passive House Association conducted CO₂ measurements in 11 Vilnius schools during winter – the season when natural ventilation is least viable and the problem most acute.

The winter context is significant. Outdoor temperatures of −1°C to +6°C represent the marginal zone in which teachers face a genuine trade-off between thermal comfort and ventilation. Opening windows at these temperatures rapidly chills the classroom, making sustained airing impractical during occupied hours. This cold-climate, sealed-building dynamic is shared across a large bloc of northern and eastern EU member states. The Lithuanian data is not an outlier.

Why Natural Ventilation Cannot Solve the Problem

Most EU member states require classrooms to be ventilated through openable windows. In practice, four structural limitations make this consistently insufficient:

Health and Learning Consequences

Sick Building Syndrome

Sick Building Syndrome (SBS) is a recognised condition associated with time spent in poorly ventilated or contaminated buildings. It is caused not by CO₂ itself, but by the broader accumulation of pollutants – biological contaminants, VOCs, fine particulate matter, and allergens – that occurs when ventilation is inadequate.

SBS typically becomes apparent at CO₂ concentrations above 1,000 ppm – the level exceeded by 81% of European classrooms. In schools, it presents as fatigue and drowsiness during lessons, headaches, eye and throat irritation, reduced capacity for reasoning and memory retention, and higher rates of illness-related absenteeism.

Allergies, Asthma & Respiratory Disease

Children with allergies or asthma face a compounded problem in naturally ventilated schools: inadequate air exchange allows pollutant concentrations to build, while during pollen season open windows import the very allergens that trigger respiratory symptoms. These two effects reinforce each other, making naturally ventilated classrooms particularly harmful for allergic and asthmatic children.

Academic Performance

Students in better-ventilated classrooms consistently achieve higher test scores, demonstrate improved attendance, and show better sustained concentration than those in poorly ventilated environments. The mechanism is physiological: inadequate ventilation reduces the brain’s oxygen metabolism, impairing precisely the cognitive functions – concentration, reasoning, memory formation – that academic learning depends on.

Sweden: A Blueprint for Healthy Learning Environments

Sweden offers a compelling example of how policy and infrastructure can transform indoor environmental quality in schools. Approximately 90% of Swedish buildings are equipped with mechanical ventilation systems, providing controlled fresh-air supply throughout the year – regardless of outdoor temperature or pollen season.

Studies in mechanically ventilated Swedish schools have consistently shown CO₂ below guideline values, reduced PM₂.₅ and PM₁₀, reduced allergen exposure through HEPA filtration, and consistent indoor conditions regardless of season. A 2000 intervention study found pupils in schools with newly installed ventilation reported significantly fewer asthmatic symptoms.[12] A 2022 Gothenburg study of 45 classrooms found CO₂, formaldehyde, PM₂.₅ and PM₁₀ consistently lower in mechanically ventilated classrooms.

Mechanical Ventilation as a Proven Solution

Mechanical ventilation provides controlled, predictable air exchange regardless of outdoor conditions: consistent fresh-air supply, controlled exchange rates, high-efficiency filtration, heat recovery, and improved comfort year-round. Modern demand-controlled ventilation (DCV) continuously adjusts airflow based on occupancy and measured CO₂, maintaining healthy conditions while optimising energy consumption.

Why Air Distribution Matters

Ventilation performance depends not only on how much air is supplied, but on how effectively it is distributed throughout the occupied space. Even a correctly sized system can fail if air distribution is poor – producing draughts, excessive noise, uneven temperatures, and air-stagnation zones.

Ventilation systems that create discomfort are frequently adjusted, restricted, or switched off by teachers – eliminating their benefits entirely. In schools, occupant comfort is not a secondary consideration. It determines whether the system is used at all.

Optimising School Ventilation Through Fabric Air Distribution

Fabric-based air distribution systems offer several characteristics that align particularly well with the requirements of educational environments.

Conclusion

Every child deserves a classroom environment that supports learning rather than limits it.

The evidence from across Europe is clear. Poor indoor air quality remains widespread in educational buildings, and elevated CO₂ – as an indicator of broader ventilation failure – continues to affect the health and learning of millions of students every day. Yet Sweden demonstrates that this is not inevitable: with the right infrastructure and policy commitment, schools can maintain clean, filtered, comfortable air throughout the year.

The solutions already exist. By combining effective mechanical ventilation, high-efficiency filtration, intelligent control strategies, and well-designed fabric air distribution systems, schools can create healthier, more comfortable, and more productive learning environments.