View all text of Subpart H [§ 51.150 - § 51.153]
§ 51.151 - Significant harm levels.
Each plan for a Priority I region must include a contingency plan which must, as a minimum, provide for taking action necessary to prevent ambient pollutant concentrations at any location in such region from reaching the following levels:
Sulfur dioxide—2.620 µg/m 3 (1.0 ppm) 24-hour average. PM