Effect of occupant-induced indoor CO2 concentration and bioeffluents on human physiology using a spirometric test

Lower ventilation rates and higher occupant density lead to accumulation of carbon dioxide (CO2) accompanied by human bioeffluents inside built environments. Research had been conducted to evaluate the effect of CO2 and bioeffluents using physiological measurements and correlated with reduced cognitive performance. However, no study has reported the underlying mechanism for the reduction in cognitive performance when exposed to elevated CO2 concentration with bioeffluents. It is suggested that the reduction in cognitive performance is due to CO2 retention in human, caused by the reduced gas transfer in lungs. The aim of the study was to obtain the lung performance functions at varying CO2 concentrations with bioeffluents and to investigate their influence on the gas exchange mechanism. A spirometric analysis was made with eight healthy male volunteers at four different exposure conditions-ambient, 1000 ppm, 2000 ppm, and 3000 ppm-for a 3-h duration. The important parameters such as forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) showed reduced value, whereas FEV1/FVC showed a stable value across exposure conditions. Evidences for a restrictive lung behavior were reported, indicating a reduced gas transfer in the lung region. The partial pressure of CO2 in lungs was derived from a literature experimental database and found to be increasing during elevated CO2 concentration with bioeffluents. The underlying mechanism for the CO2 retention in humans is elaborated.