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Code of Federal Regulations Title 40. Protection of Environment § 40.50.8 National primary ambient air quality standards for carbon monoxide

Current as of January 02, 2025 | Updated by Findlaw Staff

(a) The national primary ambient air quality standards for carbon monoxide are:

(1) 9 parts per million (10 milligrams per cubic meter) for an 8–hour average concentration not to be exceeded more than once per year and

(2) 35 parts per million (40 milligrams per cubic meter) for a 1–hour average concentration not to be exceeded more than once per year.

(b) The levels of carbon monoxide in the ambient air shall be measured by:

(1) A reference method based on appendix C and designated in accordance with part 53 of this chapter, or

(2) An equivalent method designated in accordance with part 53 of this chapter.

(c) An 8–hour average shall be considered valid if at least 75 percent of the hourly average for the 8–hour period are available. In the event that only six (or seven) hourly averages are available, the 8–hour average shall be computed on the basis of the hours available using six (or seven) as the divisor.

(d) When summarizing data for comparison with the standards, averages shall be stated to one decimal place. Comparison of the data with the levels of the standards in parts per million shall be made in terms of integers with fractional parts of 0.5 or greater rounding up.

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Cite this article: FindLaw.com - Code of Federal Regulations Title 40. Protection of Environment § 40.50.8 National primary ambient air quality standards for carbon monoxide - last updated January 02, 2025 | https://codes.findlaw.com/cfr/title-40-protection-of-environment/cfr-sect-40-50-8/

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