§7473 Increments and Ceilings

Summary

States must include actions in their air plans that keep sulfur oxides (like SO2) and tiny particles from going above set increases over the baseline and above set concentration limits. For limits tied to national air-quality rules for periods shorter than a year, the allowed increase may be exceeded once per year, except for one special allowable increase listed elsewhere in the law. The allowed increases over baseline are: for Class I areas—particulate matter annual geometric mean 5 µg/m3 and 24-hour 10 µg/m3; sulfur dioxide annual 2 µg/m3, 24-hour 5 µg/m3, 3-hour 25 µg/m3. For Class II—particulate matter annual 19 µg/m3, 24-hour 37 µg/m3; sulfur dioxide annual 20 µg/m3, 24-hour 91 µg/m3, 3-hour 512 µg/m3. For Class III—particulate matter annual 37 µg/m3, 24-hour 75 µg/m3; sulfur dioxide annual 40 µg/m3, 24-hour 182 µg/m3, 3-hour 700 µg/m3. No area's pollutant concentration can be higher than the lower of the primary or secondary national standards for the same exposure period. A Governor may, after public notice and a hearing, make rules to ignore some increases when checking compliance. These can cover rises from switching fuels under certain emergency orders, from switching because of natural gas curtailment plans, from temporary construction emissions, and from new sources outside the United States. Any such exclusion can last no more than five years after the order or plan starts (five years after the later date if both apply). The Governor must send the rule to the EPA Administrator, and it only takes effect if the Administrator approves it.