Field survey on indoor air quality was conducted in summer, autumn and winter season, in three elementary schools in Kagoshima city. In every classroom, in summer and autumn, the open degree of a opening was high, and CO_2 concentrations under pupils staying in the classroom were kept below 1000 ppm. In winter, since changing into the state where the opening was closed by the fall of temperature is expected, it is presumed in this case at the time of the lesson end for 45 minutes that indoor CO_2 concentration reaches at about 2260 ppm. The CO_2 emission rate from one sixth grader child was calculated as 0.014m^3/h. In the state where the opening was closed, by operating two sets of ventilation fans, the air change rate of 3 h^<-1> or more is secured, and it is thought that indoor CO_2 concentration is also set to below 1500 ppm at the time of the lesson end.
