| NO. | Class | API | Symbology |
| 1 | Good | <50 |
|
| 2 | Moderate | 51 - 100 |
|
| 3 | Unhealthy for sensitive groups | 101 - 150 |
|
| 4 | Unhealthy | 151 - 200 |
|
| 5 | Very unhealthy | 201> |
|