## 5 Conclusions  
Based on a preliminary experimental investigation of the National Aquatics Center Curling Gymnasium, CFD simulation technology was used in this study to simulate and analyse indoor PM\({}_{2.5}\) concentration. In addition, the effects of the outdoor weather conditions, building airtightness, and air conditioning terminal supply methods on the  
Figure 11: Air outlet of bag air duct. Figure 10: Distribution of PM\({}_{2.5}\) concentration in different indoor areas under two kinds of air supply methods: **(a)** PM\({}_{2.5}\) concentration distribution in ground air supply mode; **(b)** PM\({}_{2.5}\) concentration distribution in the cloth bag duct air supply mode. distribution of indoor PM\({}_{2.5}\) concentrations were analysed. The conclusions of this study are as follows:  
1. The outdoor PM\({}_{2.5}\) concentration significantly influenced the indoor PM\({}_{2.5}\) concentration. When the outdoor PM\({}_{2.5}\) concentration increased by 20 \(\mu\)g/m\({}^{3}\), the indoor PM\({}_{2.5}\) concentration increased by 6 \(\mu\)g/m\({}^{3}\) on average. When the outdoor PM\({}_{2.5}\) concentration reached 90 \(\mu\)g/m\({}^{3}\), the indoor PM\({}_{2.5}\) concentration exceeded the limit value of 25 \(\mu\)g/m\({}^{3}\). 2. For ice sports venues with almost no natural ventilation, fresh air systems are key to ensuring indoor air quality. 3. When the airtightness of the venue was good, that is, the infiltration and ventilation frequency was 0.15 times/hour, the outdoor air quality had no significant impact on the average indoor PM\({}_{2.5}\) concentration. With an increase in the infiltration air exchange time, the PM\({}_{2.5}\) concentration in all the regions increased. The temporary area on the eastern side was the most affected area. Compared with a ventilation rate of 0.15 times/h, the PM\({}_{2.5}\) concentration in the competition area at a ventilation rate of 0.75 times/h increased by 55 times, whereas that in the audience area had the least influence, only increasing by 21%. 4. The air supply system at the end of the air conditioner in the competition area adopted the cloth bag duct air supply mode. Compared with the ground air supply mode, the fresh air from the air conditioner could directly reach the area near the ice surface, and the air supply volume could be appropriately increased, decreasing the PM\({}_{2.5}\) concentration in the competition area by 93%. 5. Measures for improving the air quality of curling venues are as follows. 1. During the site planning process, areas with abundant greenery and good surrounding air environments should be selected as project sites as far as possible to minimise the possibility of excessive indoor particulate matter concentration. 2. From the architectural design perspective, the direct outdoor door and window openings should be reduced, a door curtain should be set up at the frequently used entrance and exit, and a curtain wall structure with strong airtightness should be used. 3. From the perspective of daily management, strengthening the airtightness of the venue, closing entrances and exits, and organising the audience and staff in a unified manner can reduce the impact of outdoor air. Conceptualization, X.D. and J.L. ; methodology, X.D. and J.L. ; software, J.L. ; validation, Z.T. ; formal analysis, Z.T. ; investigation, Z.T. and S.H. ; writing--original draft preparation, X.D.and J.L. ; writing--review and editing, Z.T. ; visualization, J.L. ; supervision, X.D. ; funding acquisition, X.D. All authors have read and agreed to the published version of the manuscript. This work was financially supported by the National Key Research and Development Program of China (NO. 2023 YFE0102100). Not applicable. Data Availability Statement: Data are contained within the article. The authors would like to thank the administrative staff from the National Aquatics Center staff for their constructive feedback during the drafting of the manuscript. Author [PERSON] was employed by China Railway First Survey and Design Institute Group Co., Ltd.