We have known for decades that indoor air in schools somehow affects students’ ability to learn. We are now seeing just how important IAQ is to healthy brain functioning.

We all know that our moods and thinking are affected by the physical world outside of our heads. Clearly this is part of our essential make-up as human beings. Less obvious is how sensations and information are exchanged between the environment and our brains, and why people in the exact same setting often react so differently. The answer to this question is complicated because human responses are determined by past as well as present stimuli. Nevertheless, as managers of the indoor environment, it is critical to understand which parameters improve or harm our desire and ability to learn new information, respond to physical threats, feel empathy toward others, and carry out the myriad of other tasks our brain is capable of doing.

One example of the interplay between sensory stimuli and emotions is the connection between daylight hours and depression. Some people are more prone to depression in the autumn and winter months when daylight hours shorten. This phenomenon, known as seasonal affective disorder, occurs as fewer hours of full spectrum sunlight decreases the number of nerve signals between the eye and the brain. Fewer nerve signals results in lower levels of some brain chemicals, or neurotransmitters, such as serotonin and dopamine. Because these chemicals are needed to maintain an optimistic mood, changes in their levels may trigger depression.

Interestingly, other studies relate dopamine to curiosity and learning. Recent brain imaging data has revealed that students with higher dopamine levels are more curious, and also learn and memorize new information more quickly than students with lower dopamine levels. Furthermore, successful learning further increases this neurotransmitter, resulting in a positive feedback loop.

It may be obvious that the more inquisitive we are about a subject, the easier it is to learn about it. More surprising, however, are findings that once our curiosity is aroused and dopamine levels are raised, a brain state results that enhances learning not only the topic you are motivated to learn but associated information as well.

Depending on your surrounding air, you may now be curious about the connection between learning and indoor air quality. The answer is most likely related to several parameters, but one important variable is the water vapor content (humidity) of indoor air. Many people in dry indoor environments, where the relative humidity is less than 40%, are mildly dehydrated because their fluid losses through breathing and skin evaporation exceed their intake through drinking and eating. Even imperceptible dehydration of 1% of our total body weight results in a temporary, yet measurable, decrease of brain tissue volume, neurotransmitter activity, and cognitive performance. When fluid loss induces a 2% or more decrease in body weight, visual-motor tracking, short-term memory, and attention become obviously impaired.

A well-done pilot study by Eric Zimmermann at the Cantonal School, Zurich, Switzerland, (“Indoor Climate – Conquerer of the students?”) yielded important and actionable results. Zimmermann measured temperature, relative humidity, and CO₂ content in eight classrooms of the Kantonsschule Baden between May and June 2017. He correlated these readings with student-reported wellbeing and, most originally, with their examination grades. In conclusion, he recommended the following indoor climate goals for optimal student performance:

• Temperature: 22 – 26°C
• Relative humidity: 40–60% rh
• CO₂ level: < 800 ppm

In summary, we must understand the importance of the indoor environment in supporting human health, learning, and productivity. Our students need schools that are properly built and maintained, with indoor climates that optimize their present-time curiosity and learning, and therefore their future success.