LouisvilleKy.gov - Air Monitoring - National Ambient Air Quality Standards (NAAQS)

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National Ambient Air Quality Standards (NAAQS)

Averaging Period	Primary Standard	Secondary Standard
Carbon Monoxide
8-hour average	9 ppm ⁽¹⁾	9 ppm ⁽¹⁾
1 hour average	35 ppm ⁽¹⁾	35 ppm ⁽¹⁾
Lead
Calendar quarter average	1.5 µg/m³	1.5 µg/m³
Nitrogen Dioxide
Annual average	0.05 ppm	0.05 ppm
Ozone
1-hour average	0.12 ppm ⁽²⁾	0.12 ppm ⁽²⁾
8-hour average	0.075 ppm ⁽³⁾	0.075 ppm ⁽³⁾
PM₁₀ (Inhalable Particulates)
Annual average	50 µg/m³ ⁽⁴⁾	50 µg/m³ ⁽⁴⁾
24-hour average	150 µg/m³ ⁽⁵⁾	150 µg/m³ ⁽⁵⁾
PM_2.5 (Fine Particulates)
Annual average	15 µg/m³ ⁽⁴⁾	15 µg/m³ ⁽⁴⁾
24 hour average	35 µg/m³ ⁽⁶⁾	35 µg/m³ ⁽⁶⁾
Sulfur Dioxide
Annual average	0.03 ppm	--
24-hour average	0.14 ppm ⁽¹⁾	--
3-hour average	--	0.50 ppm ⁽¹⁾

FOOTNOTES:

⁽¹⁾ This average is not to be exceeded more than once per year.

⁽²⁾ The standard is attained when the expected number of days per calendar year with maximum hourly average concentrations above 0.12 ppm (235 µg/m³) is equal to or less than 1 over a three-year period, as determined by Appendix H of 40 CFR 50.

⁽³⁾ The standard is attained when the three-year average of the fourth-highest daily maximum 8-hour average is less than or equal to 0.075 ppm. Revised 3/27/2008.

⁽⁴⁾ The standard is attained when the expected annual arithmetic mean concentration, as determined in accordance with Appendix K to 40 CFR 50, is less than or equal to the standard.

⁽⁵⁾ The standard is attained when the 3-year average of the annual 99th percentile concentration is less than the standard.

⁽⁶⁾ The standard is attained when the 98th percentile concentration for the year is less than the standard. Revised 10/17/2006.