Do buildings make us dumb? The effect of indoor air quality on cognition

We spend most of our time indoors. We are indoors while we sleep, while we work, when we go to the gym, and on many other occasions. Especially office workers spend a majority of their life indoors. However, it seems to be that the quality of the indoor air has a strong impact on our ability to think, solve complex problems and make thorough decisions.

Over the last decades, there has been a growing research field on the impact of indoor air quality on human cognition. It used to be that the concentration of carbon dioxide in buildings was used to assess the level of other harmful substances in the air, called volatile organic compounds, or short VOCs. VOC is an umbrella term for substances like propanol, acetone, benzene, and many others. Some of them are emitted from the building and its furniture. Especially newly constructed buildings emit a high level of VOCs from painting, carpets, copy machines, etc.

However, humans also emit certain VOCs, as a byproduct of their metabolism. These are summarized under the term “bioeffluents.” Carbon dioxide is the most prevalent gas which is emitted by humans. When we inhale, we absorb oxygen, which we need for metabolic processes in the body to gain energy, and of these processes, carbon dioxide is a byproduct, which we exhale. So, the more strenuous the work, the more energy we consume, the higher the amount of carbon dioxide we exhale.

A systematic review published last year summarizes the research about the negative effect of carbon dioxide itself, and VOCs raising together with carbon dioxide, on human cognition [Du et. al. 2020]. The results are quite astonishing. Figure 1 below shows that carbon dioxide itself has a strong negative effect on cognitive tasks such as strategic thinking, attention, and reasoning, depending on the indoor concentration. If VOCs are also high, the negative impact becomes even more prevalent (figure 2). Especially when testing with the Strategic Management Simulation (SMS), which tests higher cognitive function such as strategic thinking, decision making, and logical thinking, the effect of carbon dioxide and VOCs are quite strong. The effects on cognition can already be observed at levels between 1,500 ppm (parts per million) and 3,000 ppm. As a frame of reference: Sitting in a small room with four persons and insufficient or no ventilation introducing fresh air from outside is enough to reach levels above 3,000 ppm after two hours [Vehviläinen et al 2016]. Given that employees often sit in the office for up to eight hours per day, these levels can be easily reached.

Graph 11 2

Why is that relevant for business? Well, indicating that bad air quality in terms of high levels of carbon dioxide and VOCs impair cognition, this is highly relevant for knowledge workers. It indicates that occupational groups like managers, stock market traders, asset managers, insurance workers, but also professionals working in the military, are affected in their ability to make well-thought out and reasonable decisions in their daily work. Making suboptimal decisions, especially in the financial sector, can have direct financial costs. For office workers whose cognitive abilities are less demanded at work, lower indoor air quality can still affect well-being, thus affecting absenteeism and sick leave rates, which again have a direct cost effect due to productivity loss.

In summary, if we want workers to perform well in cognitive tasks and feel good at their workplace, we have to think about indoor air quality and how to provide optimal air conditions.


Du, B., Tandoc, M. C., Mack, M. L., & Siegel, J. A. (2020). Indoor CO2 concentrations and cognitive function: A critical review. Indoor air, 30(6), 1067-1082.

Vehviläinen, T., Lindholm, H., Rintamäki, H., Pääkkönen, R., Hirvonen, A., Niemi, O., & Vinha, J. (2016). High indoor CO2 concentrations in an office environment increases the transcutaneous CO2 level and sleepiness during cognitive work. Journal of occupational and environmental hygiene, 13(1), 19-29.