_Article_  
Analysis of Carbon Dioxide Concentration Prediction  
Model and Diffusion Tendency of Expiratory by  
Simultaneous Multipoint Sensing  
[PERSON] 1,*2, [PERSON] 2, [PERSON] 1, [PERSON] 1, [PERSON] 3, [PERSON] 4 and [PERSON] 1  
Graduate School of Media and Governance, Keio University, Fujisawa-shi 252-0882, Kanagawa, Japan; [EMAIL_ADDRESS] (K.M.); [EMAIL_ADDRESS] (K.I.); [EMAIL_ADDRESS] (Y.T.) Faculty of Data Science, Musashino University, Nishi-tokyo-shi, Tokyo 202-8585, Japan; [EMAIL_ADDRESS] YUKI Precision Co., Ltd., Yokohama-shi 222-0033, Kanagawa, Japan; [EMAIL_ADDRESS] Kankyo Research Co., Ltd., Hachioji-shi, Tokyo 192-0054, Japan; [EMAIL_ADDRESS] Correspondence: [EMAIL_ADDRESS]  
Received: 28 May 2020; Accepted: 2 July 2020; Published: 4 July 2020  
[PERSON] Abstract  
Recent indoor air quality studies show that even 1000 parts per million (ppm) concentration of Carbon Dioxide (CO\({}_{2}\)) has an adverse effect on human intellectual activities. Therefore, it is required to keep the CO\({}_{2}\) concentration below a certain value in a room. In this study, in order to analyze the diffusion tendency of carbon dioxide by breathing, we constructed a simultaneous multi-point sensing system equipped with a carbon dioxide concentration sensor to measure indoor environment. Furthermore, it was evaluated whether the prediction model can be effectively used by comparing the prediction value by the model and the actually measured value from the sensor. The experimental results showed that CO\({}_{2}\) by exhaled breathing diffuses evenly throughout the room regardless of the sensor's relative positions to the human test subjects. The existing model is sufficiently accurate in a room which has above at least a 0.67 cycle/h ventilation cycle. However, there is a large gap between the measured and the model's predicted values in a room with a low ventilation cycle, and that suggests a measurement with a sensor still is necessary to precisely monitor the indoor air quality.  
carbon dioxide concentration sensor; simultaneous multipoint sensing; indoor air quality, indoor measurement  
according to the study by [PERSON] et al. [5], it is considered to be \"Relative to 600 ppm (parts per million), at 1000 ppm CO\({}_{2}\), moderate and statistically significant decrements occurred in six of nine scales of decision-making performance.\" Thus, even concentrations as low as 1000 ppm have been shown to have an adverse effect on human decision-making. For this purpose, it is necessary to predict the change in CO\({}_{2}\) concentration and control it so that the concentration in the room is below constant. In order to maintain the quality of intellectual activity in human interaction in a room, we analyze the diffusion tendency of CO\({}_{2}\) in exhaled air and investigate a model to predict CO\({}_{2}\) concentration. Specifically, in this study, we measured and analyzed how CO\({}_{2}\) diffused in a low concentration zone, which had not been noticed until now, by simultaneous multipoint sensing. In addition, we selected a prediction model from the experimental results and compared the prediction model of CO\({}_{2}\) concentration in the existing room with the measurement device in the actual room in three different sized rooms on the same basement level of the same building, and verified whether the existing prediction model is applicable to the measurement method using the measurement device.