On May 5, the VTM news aired a report about air quality in Flemish daycare centers. The advice was familiar: ventilate regularly. This same message is often repeated in schools. And yes, ventilation does reduce CO₂ levels – an important factor in preventing fatigue and maintaining focus. But at Insightair, we believe this view is too limited. Not because CO₂ isn’t important – it is a helpful indicator of air renewal – but because it oversimplifies a much more complex issue.
Case study: air quality in Antwerp schools
Insightair is running a long-term project monitoring the air quality in about thirty schools in Antwerp. Based on the data, we provide tailored advice to help improve indoor air conditions. Each school is equipped with multiple air quality sensors, placed both indoors and outdoors. These sensors continuously track around ten parameters, including CO₂, but also traffic-related pollutants such as NO₂ and fine particulate matter.
When schools consistently ventilate by opening windows and doors, CO₂ levels tend to stay under control. However, we still see dangerously high levels of NO₂ and fine dust, particularly during rush hours. These pollutants are far more harmful than CO₂.
The dangers of NO₂ and fine particles
While high CO₂ levels can cause fatigue, headaches, or drowsiness, the effects of NO₂ and fine particles are far more severe and long-lasting. Nitrogen dioxide increases the risk of respiratory infections, asthma, chronic lung conditions, and even cancer. Fine particulate matter – especially PM2.5 – is small enough to reach deep into the lungs and even enter the bloodstream, affecting the heart, brain, and the development of the immune system.
Measure before you ventilate
Since investing in advanced ventilation systems isn’t always feasible for schools and daycare centers, we recommend placing two outdoor monitors: one on the street side and one on the playground or the quieter side of the building. This provides a localized view of outdoor air quality and allows you to ventilate strategically. These readings are far more accurate than general data from networks like VMM (www.vmm.be or www.irceline.be), which rely on around 80 stations across Flanders. In reality, air quality can vary dramatically from one street to the next. Without local measurements, decisions are based on guesswork.
Ventilation systems remain the best way to improve air quality – provided they are properly installed and fitted with the right filters, which must be replaced regularly. Even then, an outdoor sensor is a valuable tool to ensure the system responds to real-time air quality conditions.
Time for a policy shift
Government recommendations still focus on “adequate ventilation” in schools and daycare centers, without considering the quality of the outdoor air. This is shortsighted. We call for a policy that prioritizes local outdoor air measurements and ask that funding be allocated not only for ventilation systems but also for sensors. Because without knowing what you're bringing indoors, ventilation remains a gamble – one we shouldn’t risk when it comes to our children.
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