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Virginia Administrative Code
Title 9. Environment
Agency 5. State Air Pollution Control Board
Chapter 30. Ambient Air Quality Standards
12/31/2024

9VAC5-30-40. Carbon monoxide.

A. The primary ambient air quality standards are as follows:

1. Nine parts per million (10 milligrams per cubic meter) -- average eight-hour concentration not to be exceeded more than once per year.

2. 35 parts per million (40 milligrams per cubic meter) -- average one-hour concentration not to be exceeded more than once per year.

B. Carbon monoxide shall be measured by the reference method described in Appendix C of 40 CFR Part 50, or other method designated as such, or by an equivalent method.

C. An 8-hour average shall be considered valid if at least 75% of the hourly averages 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.

Statutory Authority

§ 10.1-1308 of the Code of Virginia; §§ 108, 109 and 302 of the Clean Air Act; 40 CFR Parts 50, 53 and 58.

Historical Notes

Derived from VR120-03-04, eff. January 1, 1985; amended, Virginia Register Volume 20, Issue 24, eff. September 8, 2004.

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