Author: Mahir Hafizović, Air quality and climate change consultant
Indoor air quality in classrooms has a direct impact on students’ health, comfort, and learning performance. This project investigates the effectiveness of air purifiers and their optimal placement under real classroom conditions. Experimental measurements were conducted, where PM2.5 particle concentrations were monitored using multiple sensors placed at various heights and locations. Artificial smoke was introduced to simulate high pollution levels typical of winter conditions in Sarajevo. Six different air purifier configurations were tested, varying in number, position, and airflow rate. In parallel, Computational Fluid Dynamics (CFD) simulations were performed to analyze airflow patterns, pollutant dispersion, and overall air mixing efficiency.
Why Indoor Air Quality in Classrooms Matters More Than We Think
When we think of a healthy school environment, we often imagine comfortable desks, modern technology, and bright classrooms. Yet one of the most important elements for students’ health and learning often goes unnoticed – the air they breathe.
Children are particularly sensitive to polluted air. They breathe faster than adults and often through their mouths, which means they inhale larger amounts of pollutants. Because their lungs and immune systems are still developing, they are more vulnerable to fine dust particles and gases that can linger indoors. Spending six to eight hours a day in classrooms, students are constantly exposed, and the air they breathe affects their focus, alertness, and overall health.
In many schools, especially in winter, windows are kept shut to retain heat. Classrooms become crowded, and fresh air circulation is limited. Meanwhile, outdoor pollution levels rise sharply, particularly in cities like Sarajevo, which ranks among the most polluted in the world during winter months.
Research: How Effective Are Air Purifiers?
To understand how classroom air quality can be improved, we carried out a research project testing the effectiveness of air purifiers under real classroom conditions. The aim was to find the best number, placement, and operating strategy of purifiers to ensure clean air, even when outside pollution was severe.
The classroom used in the experiment measured 13.6 × 6.8 × 3.5 meters and contained 25 desks and chairs, a typical school setting. Five PM2.5 sensors were installed around the room – on walls, desks, and under desks – to measure pollutant levels. Artificial smoke was then introduced until the concentration reached 250 μg/m³, replicating the heavy pollution often seen during Sarajevo winters.
Once the concentration stabilized, the purifiers were switched on and monitored for two hours. Six different scenarios were tested, varying the number of devices, their placement, and the airflow speed.
CFD Simulations: A Digital View of Airflow
Alongside the experiments, we used Computational Fluid Dynamics (CFD) simulations to visualize how air moves and mixes within the classroom. This digital approach helped us see where polluted air tends to accumulate and how purifier placement influences airflow.
Results: How Many Purifiers Do We Really Need?
The findings were clear:
- Three air purifiers cleaned the air the fastest and most completely. After one hour, PM2.5 levels dropped to 7.4% of the original concentration, and after two hours, only 1.4 μg/m³ remained.
- Two purifiers also performed well, but placement mattered greatly. The best results came when one was placed near the floor and the other near the ceiling, which helped circulate air evenly.
- One purifier, even at full power, was not enough for a room of this size. After two hours, pollution levels were still above safe limits.
What Does This Mean for Schools and Students?
The study highlights an important point: indoor air is not clean just because windows are closed and the classroom looks tidy. Fine particles like PM2.5 can cause lasting health effects – from respiratory infections and headaches to fatigue and reduced cognitive performance.
The good news is that the solution does not have to be expensive. Even simple air purifiers, when properly positioned, can significantly improve classroom air quality in under an hour. CFD simulations can further help determine the most effective number and placement of devices, saving energy and costs in the long run.
Conclusion
Clean air in classrooms is not just a technical concern; it is a question of children’s health and their ability to learn. Our research shows that with the right use of air purifiers, a polluted classroom can quickly become a safe and healthy learning space.
Investing in clean air is investing in the future, because every child deserves a classroom where they can breathe easily, think clearly, and grow freely.
For additional information on the project and its results check out our brochure at: Čistiji zrak za bolje učenje – brošura – Enova
The project “Optimization of Air Purification Technologies in Classrooms through Measurements and CFD Simulations” is being implemented under an R&D grant scheme jointly funded by the Federal Ministry of Education and Science and the United Nations Development Programme (UNDP) in Bosnia and Herzegovina through the project “Better Governance for Faster Economic Growth (EGG2)”, financed by the Government of the Kingdom of Norway, and the program “Translating the Framework for Implementing Sustainable Development Goals in BiH into Sustainable and Inclusive Growth (SDG2BIH)”, funded by Sweden.
