Abstract: In order to analyze the variation of indoor carbon dioxide concentration with various parameters,the theoretical formula and orthogonal experimental design method are used to theoretically analyze the indoor CO₂ concentration. Based on the relevant hypotheses, the relationship between indoor CO₂ concentration and indoor initial CO₂ concentration, outdoor CO₂ concentration, fresh air volume, exhaust air volume, indoor number of people, CO₂ concentration produced by human and other parameters are derived. Four factors including outdoor air CO₂ concentration, number of indoor people, fresh air volume and exhaust air volume are selected, and three levels of each factor are selected for orthogonal experimental design. Through the mean and range analysis, the exhaust air volume has the greatest impact on the stable value of indoor CO₂ concentration and the time required to reach the stable value in these four factors. According to the final optimization scheme determined by orthogonal analysis, the stable value of indoor CO₂ concentration is 109 ppm, and the time required to reach the stable value is 3.2 h. Therefore, in addition to ensuring sufficient fresh air volume, it is also necessary to exhaust the indoor dirty air as soon as possible in the design of fresh air function.

Key words: Orthogonal experiment, Theoretical analysis, Indoor carbon dioxide concentration