Area class | Design value* | Primary standard attainment date** |
---|---|---|
Marginal | 0.121 up to 0.138 | 3 years after November 15, 1990 |
Moderate | 0.138 up to 0.160 | 6 years after November 15, 1990 |
Serious | 0.160 up to 0.180 | 9 years after November 15, 1990 |
Severe | 0.180 up to 0.280 | 15 years after November 15, 1990 |
Extreme | 0.280 and above | 20 years after November 15, 1990 |
*The design value is measured in parts per million (ppm). | ||
**The primary standard attainment date is measured from November 15, 1990. |