52.671—Classification of regions.
The Idaho plan was evaluated on the basis of the following classifications:
| Air quality control region | Pollutants | ||||
|---|---|---|---|---|---|
| Particulate matter | Sulfur oxides | Nitrogen dioxide | Carbon monoxide | Ozone | |
| Eastern Idaho Intrastate | I | II | III | III | III. |
| Eastern Washington Northern Idaho Interstate (Idaho) | I | II | III | III | III. |
| Idaho Intrastate | I | III | III | III | III. |
| Metropolitan Boise Intrastate | II | III | III | I | III. |