Cal. Health & Safety Code § 40921.5
(a) For purposes of classifying ozone nonattainment areas pursuant to Sections 40918, 40919, 40920, and 40920.5, the terms moderate, serious, severe, and extreme shall be defined as follows:
| (1) Moderate | greater than 0.09 to not more than 0.12 parts per million, inclusive. |
| (2) Serious | 0.13 to 0.15 parts per mil- lion, inclusive. |
| (3) Severe | 0.16 to 0.20 parts per mil- lion, inclusive. |
| (4) Extreme | greater than 0.20 parts per million. |
(b) For the purposes of classifying carbon monoxide nonattainment areas under Sections 40918 and 40919, the terms moderate and serious shall be defined as follows:
| (1) Moderate | greater than 9.0 to 12.7 parts per million, inclusive. |
| (2) Serious | greater than 12.7 parts per million. |