Physiology or Psychology: What Drives Human Emissions of Carbon Dioxide and Ammonia?

Humans are the primary sources of CO 2 and NH 3 indoors. Their emission rates may be influenced by human physiological and psychological status. This study investigated the impact of physiological and psychological engagements on the human emissions of CO 2 and NH 3 . In a climate chamber, we measured CO 2 and NH 3 emissions from participants performing physical activities (walking and running at metabolic rates of 2.5 and 5 met, respectively) and psychological stimuli (meditation and cognitive tasks). Participants' physiological responses were recorded, including the skin temperature, electrodermal activity (EDA), and heart rate, and then analyzed for their relationship with CO 2 and NH 3 emissions. The results showed that physiological engagement considerably elevated per-person CO 2 emission rates from 19.6 (seated) to 46.9 (2.5 met) and 115.4 L/h (5 met) and NH 3 emission rates from 2.7 to 5.1 and 8.3 mg/h, respectively. CO 2 emissions reduced when participants stopped running, whereas NH 3 emissions continued to increase owing to their distinct emission mechanisms. Psychological engagement did not significantly alter participants' emissions of CO 2 and NH 3 . Regression analysis revealed that CO 2 emissions were predominantly correlated with heart rate, whereas NH 3 emissions were mainly associated with skin temperature and EDA. These findings contribute to a deeper understanding of human metabolic emissions of CO 2 and NH 3 .