There is increasing evidence that higher levels of carbon dioxide (CO₂) inside buildings are negatively associated with cognitive performance and the health of occupants. Many studies measure CO₂ to estimate indoor air quality because CO₂ concentrations are strongly correlated with other substances such as volatile organic compounds (VOC). However, it is still unclear if the VOCs or CO₂ itself can cause such effects. As such, also studies performed in a respiration chamber could be affected by high CO₂ concentrations inside the chamber. This interdisciplinary project aims to contribute new insights by examining the effect of long-term exposure to CO₂ on the cognitive and physiological responses of humans.
The study used a cross-over design, in which 20 healthy white-collar workers were exposed two test days of eight hours to either 0.08% CO₂ or 0.3% CO₂ in a respiration chamber. VOCs were filtered out from the air to examine the pure effect of CO₂. Cognition was measured using the CANTAB Cognition test, multiple price lists from economics literature and a perception questionnaire. Physiological parameters such as oxygen consumption, heart rate, respiration rate, blood CO₂ concentration, blood pressure, and skin temperature were measured continuously.
Preliminary analysis indicates significant improvement in short-term memory with elevated CO₂ levels. Blood CO₂ partial pressure and respiration rate were significantly reduced during the high indoor CO₂ condition with increasing exposure time. Both results show effects counterfactual to the hypotheses. No effect on parameters of economic decision-making has been found. The questionnaire for perception shows that individuals were not able to detect an elevated level of CO₂ as worse air quality. These preliminary results indicate that studies need to distinguish between the effect of indoor CO₂ and VOCs on cognition. However, further analysis including multiple hypotheses testing has to be conducted to evaluate the robustness of the presented effects.