## 3 Results  
Table 1 shows the descriptive statistics of 24-h average indoor and outdoor air pollutants, temperature, and relative humidity in 60 houses. When indoor air pollutants were paired with outdoors within the same home, we found that the 24-hour average concentrations of indoor CO, CO\({}_{2}\), and NO\({}_{2}\) were significantly higher than the 24-hour average of outdoors concentrations, whereas, outdoor O\({}_{3}\) and PM\({}_{2.5}\) concentrations were significantly higher than indoor concentrations (all \(p<0.01\)). The average distance between homes of subjects and their school were 0.86 km, 0.94 km, and 1.46 km in general, traffic, and industrial areas, respectively, as well as, the average distance between homes of subjects and the nearest air monitoring station were 1.07 km, 0.97 km, and 1.46 km in general, traffic, and industrial areas, respectively. In comparison with household air pollutants of three areas, Table S1 shows descriptive statistics of 24-h average concentration of indoor air pollutants in the houses of traffic, industry, and general areas. Figure 1 shows the 24-h average concentration of indoor air pollutants (A) CO, (B) CO\({}_{2}\), (C) NO\({}_{2}\), and (D) O\({}_{3}\) in the houses of traffic, industry, and general areas. We found the 24-hour average concentration of indoor CO concentration of the traffic area was significantly higher than that of the industrial area, and the general area with all \(p<0.01\) (Figure 1, Table S1). In addition, the 24-hour average concentration of indoor CO\({}_{2}\) level of the general area was significantly lower than that of the traffic area, and industrial area (all \(p<0.01\)) (Figure 1, Table S1). Finally, both the 24-hour average concentration of household NO\({}_{2}\) and O\({}_{3}\) concentrations of the industrial area were significantly lower than that of the traffic area, and general area (all \(p<0.01\)) (Figure 1, Table S1). Moreover, there was no  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline  & & **Mean** & **Median** & \begin{tabular}{c} **Standard** \\ **Deviation** \\ \end{tabular}  & **Minimum** & **Maximum** & \(p\)**-Value \({}^{\text{\#}}\) \\ \hline CO (ppm) & indoor & 3.47 & 0.83 & 4.29 & 0.00 & 12.27 & \\  & outdoor & 0.60 & 0.38 & 0.55 & 0.00 & 1.98 & 0.004 \({}^{\text{\ddagger}}\) \\ CO\({}_{2}\) (ppm) & indoor & 655.43 & 479.55 & 321.60 & 413.82 & 1320.00 & \\  & outdoor & 322.22 & 319.92 & 17.23 & 285.83 & 353.90 & \textless{}0.001 \({}^{\text{\ddagger}}\) \\ NO\({}_{2}\) (ppb) & indoor & 185.30 & 177.97 & 41.52 & 127.28 & 251.41 & 0.008 \({}^{\text{\ddagger}}\) \\  & outdoor & 107.54 & 118.22 & 36.83 & 39.90 & 149.80 & \\ SO\({}_{2}\) (ppm) & indoor & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 & 0.193 \\ O\({}_{3}\) (ppb) & outdoor & 0.01 & 0.00 & 0.02 & 0.00 & 0.06 & 0.193 \\  & indoor & 11.04 & 8.50 & 8.93 & 1.06 & 32.29 & \\  & outdoor & 13.46 & 9.20 & 12.34 & 0.24 & 45.50 & 0.006 \({}^{\text{\ddagger}}\) \\ PM\({}_{2.5}\) (\(\mathrm{\SIUnitSymbolMicro g}\)/m\({}^{3}\)) & indoor & 60.00 & 40.00 & 50.00 & 10.00 & 210.00 & \\  & outdoor & 110.00 & 90.00 & 90.00 & 30.00 & 410.00 & 0.001 \({}^{\text{\ddagger}}\) \\ Temperature (\({}^{\text{\text{\textstatistical significant difference of the 24-hour average concentration of indoor SO\({}_{2}\) and PM\({}_{2.5}\) between the three areas (Table S1). Table 2 shows the percentage of household characteristics including window opening, residents >4 people, cooking, etc. in traffic, industry, and general areas. We found compared with traffic area and industrial area, the general area had a higher percentage of window opening, cooking, and air-conditioning use; moreover, a lower percentage of residents > 4 people, smoker, incense burning, mosquito coil burning, and essential oil using. The following Table 3 shows the ratios of air pollutants during window opening periods to the reference periods and the differences in air pollutants between window opening periods and reference periods.