Table 2.
Distribution of home characteristics, surrounding land use, and questionnaire variables related to indoor air pollution.
| Mean | SD | Min | Median | Max | |
|---|---|---|---|---|---|
| Variables | |||||
| Percent urban spaces within 1 km2 grid (%) | 67 | 27 | 0 | 74 | 100 |
| Major road density within 1 km2 grid (no. of vehicle·km/km2) | 2.2 | 1.6 | 0.0 | 2.0 | 11.5 |
| Distance to central site (km) | 27.7 | 20.2 | 1.2 | 24.5 | 88.2 |
| Building age (years) | 62.8 | 31.9 | 9.0 | 51.0 | 171.0 |
| No. of air conditioning | 2.2 | 0.7 | 1.0 | 2.0 | 4.0 |
| Use of forced air heating (# subject-week) | Yes | No | |||
| 66 | 262 | ||||
| Questionnaire | |||||
| (1) How many hours was the window open during sampling session? | 31.4 | 57.1 | 0.0 | 0.0 | 168.0 |
| (2) How many hours did you use an electric space heater during sampling session? | 5.5 | 6.8 | 0.2 | 3.0 | 24.0 |
| (3) How many hours did you use an air purifier during sampling session? | 10.1 | 33.6 | 0.0 | 0.0 | 168.0 |
| (4) What fuel do you use for heating? (# homes) | Gas | Electric | Other/oil | ||
| 44 | 21 | 30 | |||