## 5 Comparison of Predicted and Measured Values Using a Prediction Model
### Environment and Methods  
In this chapter, we compare and analyze the change in CO\({}_{2}\) concentration measured by the measurement device and the change in concentration by CO\({}_{2}\) concentration prediction model described in chapter 3, when the room volume and the number of subjects are different. Essentially, the prediction model for gas concentration is predicated on steady-state or instantaneous uniform diffusion, and since human exhalation is not instantaneous uniform diffusion, it does not satisfy that prerequisite. However, from the results of the experiments in Section 4, it was confirmed that the CO\({}_{2}\) concentration in the room increased uniformly within the error range of the sensor under the condition of one-minute intervals. Based on these experimental results, we considered that the concentration in the room increased near the measurement point in the same way as instantaneous uniform diffusion, albeit quasi-uniformly, and applied the prediction model. In the experiment, we measured the increase of CO\({}_{2}\) concentration in three rooms of different sizes (large, medium and small studios) on the same basement level in the same building, where two, four and six subjects waited for the experiment. The duration of the experiment was set at 30 min, and the volume of the studio was 197.0 m\({}^{3}\) for the large studio, 48.5 m\({}^{3}\) for the medium studio and 22.2 m\({}^{3}\) for the small studio, with heights of 3.8 m, 2.5 m and 3 m, respectively. Six measuring devices were installed in the room, and considering the sensor error, the change of CO\({}_{2}\) concentration in the room was defined as the average of four values excluding the two measuring devices with the maximum and minimum increase in the final CO\({}_{2}\) concentration. The measurement device was placed on the floor and its height was set at 0 m. Figure 11 shows the arrangement of the subjects in each room and their distances. In this experiment, the measurement device is placed under the chair in which the subject is seated, and the distance from the subject is almost non-existent. Four experiments were conducted under each condition, and the mean value of the experiment was used as the experimental result. As in Section 4, the room temperature was measured every minute during the experiment to show that there was no sudden temperature change in the room. In order to increase the CO\({}_{2}\) concentration in the room in a short time and with a small number of subjects, the ventilation openings and gaps between the doors were covered with liner. In addition, the studio used in the experiment was a basement room, and there were no windows or other openings. After the experiment, in order to keep the effect of ventilation volume other than volume and the change in ventilation volume from experiment to experiment small, one of the air conditioning linings and one of the door linings were removed, the air conditioning was activated and the subjects were exited. After confirming that the CO\({}_{2}\) concentration in the room decreased to the same level as the outside air in the building (about 400 to 500 ppm by the measurement device), we started the next experiment. The parameter of the number of ventilation cycles in each studio was determined under the following conditions: a measurement device was installed in each room as shown in Figure 12, the CO\({}_{2}\) concentration in the room was measured and the average value of the CO\({}_{2}\) concentration in the room was taken as the CO\({}_{2}\) concentration in the room. D1, D2 and D3 were placed on the floor (0 m height), while D4, D5 and D6 were placed at the same location and at different heights (0 m, 1 m and 2 m), and each device was placed about 10 cm away from the nearest wall except for D2. Next, a maximum of 10 subjects were placed in a room and the CO\({}_{2}\) concentration in the room was increased to more than 2000 ppm. Afterward, the subjects left and the door was reattached from the outside.