Echelle en microgrammes/m3
 | < = 30 (excellent) |
 | 31-50 (very good) |
 | 51-70 (good) |
 | 71-90 (quite good) |
 | 91-110 (average) |
 | 111-145 (poor) |
 | 146-180 (very poor) |
 | 181-240 (bad) |
 | 241-360 (very bad) |
 | > 360 (execrable) |
| < = 30 (excellent) |
| 31-50 (very good) |
| 51-70 (good) |
| 71-90 (quite good) |
| 91-110 (average) |
| 111-145 (poor) |
| 146-180 (very poor) |
| 181-240 (bad) |
| 241-360 (very bad) |
| > 360 (execrable) |