Echelle en microgrammes/m3
 | < = 10 (excellent) |
 | 11-20 (very good) |
 | 21-30 (good) |
 | 31-40 (quite good) |
 | 41-50 (average) |
 | 51-70 (poor) |
 | 71-100 (very poor) |
 | 101-150 (bad) |
 | 151-200 (very bad) |
 | > 200 (execrable) |
| < = 10 (excellent) |
| 11-20 (very good) |
| 21-30 (good) |
| 31-40 (quite good) |
| 41-50 (average) |
| 51-70 (poor) |
| 71-100 (very poor) |
| 101-150 (bad) |
| 151-200 (very bad) |
| > 200 (execrable) |