Impact of experimentally elevated CO₂ concentrations and temperature on cognitive function: An EEG-based study under constant ventilation

Global warming is expected to alter indoor thermal environments and indoor air composition, yet the specific effects of these changes on learning and cognition remain insufficiently understood. In this climate chamber study, we examined the combined effects of experimentally elevated indoor CO₂ concentrations (500 and 5000 ppm, added from a gas cylinder under constant ventilation) and temperatures (22 °C and 28 °C) on cognitive-related outcomes. Twenty-four participants completed a within-subject protocol involving two neuropsychological tasks (Stroop and delayed-matching-to-sample), subjective evaluations, physiological measurements, and electroencephalography (EEG). EEG features were further used to construct a deep learning-based Cognitive Comfort Model (CCM). Significant interactions between CO₂ level and temperature were observed for noise acceptability, thermal comfort, and EEG power in the alpha, theta, and delta bands, whereas behavioral task performance showed only limited changes across conditions. These results suggest that combined thermal-CO₂ stress can modulate subjective comfort and neural indicators of cognitive load even when overt performance is largely preserved. Our findings help to clarify the specific effects of elevated CO₂ and temperature, independent of general poor ventilation, and support the refinement of indoor environmental control strategies aimed at protecting cognitive well-being in warming climates.