Air quality in the car: How CO₂ and body odor affect drivers' cognition and driving performance?

Elevated indoor levels of CO₂ and the presence of body odor have been shown to have adverse effects on the cognitive function of building occupants. These factors may also contribute to impaired in-car driving performance, potentially posing a threat to transportation and public safety. To investigate the effects of CO₂ and body odor on driving performance, we enrolled 25 participants in highway driving tasks under three indoor CO₂ levels (800, 1800, and 3500 ppm) and two body odor conditions (presence and absence). CO₂ was injected in the cabin to increase CO₂ levels. In addition, we assessed working memory and reaction time using N-back tasks during driving. We found that driving speed, acceleration, and lateral control were not significantly affected by either CO₂ or body odor. We observed no significant differences in sleepiness or emotion under varying CO₂ or body odor conditions, except for a lower level of emotion valence with exposure to body odor. Task load was also not significantly impacted by CO₂ or body odor levels, except for a higher reported effort at 1800 ppm compared to 800 ppm CO₂. However, participants did demonstrate significantly higher accuracy with increased body odor exposure, suggesting a complex effect of volatile organic compounds on driver cognition. Our findings also revealed moderating effects of task difficulty of N-back tests and exposure duration on cognition and driving performance. This is one of the first few in-depth studies regarding environmental factors and their effect on drivers' cognition and driving performance, and these results provide valuable insights for car-cabin environmental design for air quality and driving safety.