Discussion on outdoor air rate index in middle school classrooms

Natural ventilation is usually acquired in the classrooms in China. Such method cannot provide enough outdoor air rate under certain situation so that the carbon dioxide (CO2) concentration often exceeds the limit. Analyses the relationship between the CO2 concentration and the outdoor air rate with an engineering case, and validates the calculation strategy with the experimental data. Compares the provisions of CO2 concentration limit and minimum outdoor air rate of the classroom in different standards of China, points out their differences, and recommends strengthening basic researches and coordinating relevant standards. By comparing different standards, finds that the minimum outdoor air rate in the standard GB 50736-2012 Design code for heating ventilation and air conditioning of civil buildings could yield the lowest CO2 concentration of the classroom when the occupant density is higher than 0.4 person per square meter.