High CO₂ exposure due to facemask wear is unlikely to impair cognition even in a warm environment after a long-term adaptation

There is a lack of consensus regarding the impact of elevated indoor CO₂ exposure on cognition. COVID-19 provided an opportunity to study responses to long-term elevated CO₂ exposure from facemask wear. Such an opportunity allows us to avoid exposing participants to elevated CO₂ levels not typically experienced in real-life settings, potentially increasing the ecological validity of our experimental design. Further, the worsening warmness during summer necessitates studies and understanding of peoples’ cognition with combined stressors of both heat and CO₂ accumulation. In this work, we recruited 60 college students to understand whether facemask wear elevates local CO₂ levels and, if so, the extent to which it impacts cognition in warm conditions. Subjects remained in a controlled summer environmental room (temperature 31.5 °C, relative humidity 30 %) for 90 min with or without facemasks. Participants completed six cognitive tests in a random order and answered surveys using computer-based software. Ten experimental subjects had a second 30 min visit to measure CO₂ concentration at the ala of the nose with and without surgical masks. The results show that wearing a surgical mask sharply increased CO₂ concentration near the nose by 15,000 ppm. Our analysis showed that the experimental group with facemask wear did not exhibit significantly different cognition performance except for short-term memory which was higher instead of lower than the control group. Participants with facemask wear showed significantly lower risk-taking, possibly attributed to thermal discomfort. Nevertheless, no significance in cognition or decision-making was observed after controlling the familywise error rate using the Bonferroni correction. We hypothesize that the insignificant difference might be caused by adaptation to long-term wear and high CO₂ exposure in daily life during COVID-19, which cannot be revealed in the studies prior to the pandemic.