The corresponding specific index of ozone is determined by fitting the concentration of the average hourly concentrations in one of the fields listed in the following table:
| Field of ozone concentrations (ug / m3) | specific index |
| 0-50 |
1
|
| 50-100 |
2
|
| 100-130 |
3
|
| 130-240 |
4
|
| 240-380 |
5
|
| 380-800 |
6
|