Paired Student's *t*-test, ‡ *p* < 0.01.

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) CO2, (C) NO2, and (D) O3 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 CO2 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 NO2 and O3 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

statistical significant difference of the 24-hour average concentration of indoor SO2 and PM2.5 between the three areas (Table S1).

**Figure 1.** The 24-h average concentration of indoor air pollutants (**A**) CO, (**B**) CO2, (**C**) NO2, and (**D**) O3 in the houses of traffic, industry, and general areas. \* Scheffe test *p* < 0.01.

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 airconditioning use; moreover, a lower percentage of residents > 4 people, smoker, incense burning, mosquito coil burning, and essential oil using.


**Table 2.** The percentage (%) of household characteristics in traffic, industry, and general areas.

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. The median ratios of pollutants during window opening periods to the reference periods for NO2 and PM2.5 were 1.56 and 1.13, respectively with the maximum values up to 5.23 and 1.85 respectively (Table 3). The NO2 and PM2.5 levels during window opening periods were significantly higher than that of the reference periods, and the maximum increased values were 53.25 ppb and 44 μg/m3, respectively. Table 4 shows the ratios of air pollutants during cooking periods to reference

periods and the differences in air pollutants between window opening periods and reference periods. The median ratios of pollutants during cooking periods to the reference periods for CO, CO2, NO2, and PM2.5 were 0.93, 1.06, 1.11, and 1.09, respectively. The concentrations of CO2, NO2, and PM2.5 during the cooking periods were significantly higher than those of reference periods with increased concentrations of 26.17 ppm, 5.40 ppb, and 5 μg/m3, respectively. However, the CO level during cooking periods was significantly lower than that of the reference periods with the decreased concentration of 0.25 ppm.

**Table 3.** The ratios of air pollutants during window opening periods to reference periods and the differences in air pollutants between window opening periods and reference periods.

