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The Code of Federal Regulations (CFR) annual edition is the codification of the general and permanent rules published in the Federal Register by the departments and agencies of the Federal Government produced by the Office of the Federal Register (OFR) and the Government Publishing Office.

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Title 40Chapter ISubchapter CPart 51Subpart H → §51.151

Title 40: Protection of Environment
Subpart H—Prevention of Air Pollution Emergency Episodes

§51.151   Significant harm levels.

Each plan for a Priority I region must include a contingency plan which must, as a mimimum, 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/m3 (1.0 ppm) 24-hour average.

PM10—600 micrograms/cubic meter; 24-hour average.

Carbon monoxide—57.5 mg/m3 (50 ppm) 8-hour average; 86.3 mg/m3 (75 ppm) 4-hour average; 144 mg/m3 (125 ppm) 1-hour average.

Ozone—1,200 ug/m3 (0.6 ppm) 2-hour average.

Nitrogen dioxide—3.750 ug/m3 (2.0 ppm) 1-hour average; 938 ug/m3 (0.5 ppm) 24-hour average.

[51 FR 40668, Nov. 7, 1986, as amended at 52 FR 24713, July 1, 1987]

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