Indoor CO2 concentrations exceeded the ASHRAE standard due to overcrowded classrooms and inadequate ventilation. Implementation of more breaks and recesses between classes might alleviate the high level of CO2. The occupancy of classrooms in Hong Kong often exceeded the maximum occupancy of the ASHRAE 62-1989 standard. Decreasing the number of students in each classroom can also lower the CO2 level. Increase the rate of ventilation could remove the accumulated CO2; for example, the use of ceiling fans, exhaust fans could increase the exchange of indoor air with the outdoor.
Children in schools constitute a particularly vulnerable population group to indoor air quality, because of their physiological and behavioural characteristics. They have higher ventilation rates and higher levels of physical activity with the result that they receive much higher doses of air pollutants than adults.
This study investigated the effect of blood CO2 levels on brain activity from a number of perspectives. We first showed that hypercapnia reduced metabolic activity in the brain. Second, neural activity was assessed indirectly by BOLD fcMRI and the data suggested that CO2 inhalation caused a decrease in spontaneous brain connectivity. Finally, EEG was used as a direct measure of neural activity and the results showed that hypercapnia caused a relative increase in lower frequency power spectra. Overall, our data showed a suppressive effect of CO2 on brain activity.