Indoor carbon dioxide (CO2) concentration significantly influences office workers’ cognitive performance, yet the neurobehavioral mechanisms linking exposure to task efficiency remain insufficiently understood. This study investigates how varying indoor CO2 concentrations (500, 1000, and 2500 ppm) impact task efficiency (accuracy and reaction time) through neurophysiological pathways grounded in Cognitive Load Theory. Using a within-subject repeated-measures design, 20 participants performed three office tasks—numerical verification, text entry, and reading comprehension—while behavioral metrics, daytime sleepiness, and electroencephalography (EEG) signals were recorded. Results demonstrate that increasing CO2 concentration monotonically decreased mean accuracy from 93.50% at 500 ppm to 80.89% at 2500 ppm, while mean reaction time rose from 2.00 s to 2.74 s. Daytime sleepiness significantly mediated the CO2–accuracy relationship. Furthermore, task type significantly moderated this effect (β = −6.182, p = 0.0289), with accuracy declines being more pronounced in tasks with higher intrinsic cognitive demand. EEG spectral analysis corroborated these findings, revealing systematic reductions in beta and theta power under elevated CO2. These findings indicate that CO2 acts as an extraneous cognitive load interacting with intrinsic task demands, providing a neurobehavioral basis for developing cognitive-aware environmental control strategies in intelligent buildings.
Zhou et al. (Sat,) studied this question.