## 3 Data Analysis  
### Analysis of Simulation Results for the Four Scenarios  
The simulation results for Scenarios 1 and 2 are presented in Figures 3 and 4, respectively. In Scenario 1, the outdoor air quality was good (the PM\({}_{2.5}\) concentration was approximately 40 \(\upmu\)g/m\({}^{3}\)), whereas the indoor PM\({}_{2.5}\) concentration was generally low. In Scenario 2, the indoor PM\({}_{2.5}\) concentration increased significantly. Compared to Scenario 1, the outdoor air quality deteriorated, with the AQI increasing from 66 to 181, and the outdoor PM\({}_{2.5}\) particle concentration increasing from 50 to 140 \(\upmu\)g/m\({}^{3}\) (Table 2). Although the average concentration in the competition area was approximately 12 \(\upmu\)g/m\({}^{3}\), which satisfied standard requirements, the PM\({}_{2.5}\) concentration in the audience area increased significantly, and the average concentration was approximately 65 \(\upmu\)g/m\({}^{3}\), which exceeded the standard limit. This is because the decrease in outdoor air quality results in an increase in the amount of particulate matter entering through the seat fresh air, and the competition area is less affected by variations in the outdoor PM\({}_{2.5}\) concentration, owing to the low amount of fresh air. In Scenario 2, the PM\({}_{2.5}\) concentration in the central corridor of the audience area and the upper part of the east and west sides of the audience seats were relatively high (approximately 40 \(\upmu\)g/m\({}^{3}\)). This is because the middle corridor is prone to forming air vortices, which can lead to the accumulation of PM\({}_{2.5}\). The east and west sides of the audience area were close to the return air vents, and the wind speed was high, which could easily cause an increase in the PM\({}_{2.5}\) concentration.  
The simulation results for Scenarios 3 and 4 are presented in Figures 5 and 6. The outdoor air quality deteriorated, with the AQI increasing from 30 to 171, and the outdoor PM\({}_{2.5}\) concentration increasing from 4 to 94 \(\upmu\)g/m\({}^{3}\). The indoor PM\({}_{2.5}\) concentration increased significantly, but the average concentration was approximately 10 \(\upmu\)g/m\({}^{3}\). None exceeded the standard limits, particularly the PM\({}_{2.5}\) concentration in the audience area, which was effectively controlled.  
Figure 3: Scene 1 indoor PM\({}_{2.5}\) concentration distribution: (**a**) distribution of PM\({}_{2.5}\) concentration in Y = 35 m cross section; (**b**) PM\({}_{2.5}\) concentration distribution at a cross section 1.5 m above ground level.  
Compared with Scenario 2, Scenario 4 also has poor air quality; however, the PM\({}_{2.5}\) concentrations in the venues decreased from 8-86 to 1-14 \(\mathrm{\SIUnitSymbolMicro g}/\mathrm{m}^{3}\). Among them, the improvement was more significant in the spectator area, where the highest PM\({}_{2.5}\) concentration decreased from 86 to approximately 10 \(\mathrm{\SIUnitSymbolMicro g}/\mathrm{m}^{3}\).  
Figure 4: Scene 2 indoor PM\({}_{2.5}\) concentration distribution: (**a**) distribution of PM\({}_{2.5}\) concentration in Y = 35 m cross section; (**b**) PM\({}_{2.5}\) concentration distribution at a cross section 1.5 m above ground level.  
Figure 5: Scene 3 indoor PM\({}_{2.5}\) concentration distribution: (**a**) distribution of PM\({}_{2.5}\) concentration in Y = 35 m cross section; (**b**) PM\({}_{2.5}\) concentration distribution at a cross section 1.5 m above ground level.  
Figure 6: Scene 4 indoor PM\({}_{2.5}\) concentration distribution: (**a**) distribution of PM\({}_{2.5}\) concentration in Y = 35 m cross section; (**b**) PM\({}_{2.5}\) concentration distribution at a cross section 1.5 m above ground level.