Wisconsin Administrative Code
Department of Natural Resources
NR 400-499 - Environmental Protection - Air Pollution Control
Chapter NR 404 - Ambient Air Quality
Section NR 404.04 - Ambient air quality standards

Universal Citation: WI Admin Code ยง NR 404.04

Current through August 26, 2024

(1) APPLICABILITY OF AIR STANDARDS. The air standards apply to the entire state without exception.

(2) SULFUR OXIDES.

(a) Primary standard. The primary standard for sulfur oxides, measured as sulfur dioxide, is 0.075 ppm - maximum 1-hour concentration. The 1-hour primary standard is met at an ambient air quality monitoring site when the 3-year average of the annual (99 th percentile) of the daily maximum 1-hour average concentrations is less than or equal to 0.075 ppm, as determined by the methodology of 40 CFR part 50, Appendix T, incorporated by reference in s. NR 484.04(7m).

(b) Secondary standard. The secondary standard for sulfur oxides, measured as sulfur dioxide, is: 0.5 ppm - maximum 3-hour average concentration, not to be exceeded more than once per year.

(4) CARBON MONOXIDE: PRIMARY AND SECONDARY STANDARDS. The primary and secondary standards for carbon monoxide are:

(a) 10 milligrams per cubic meter (9 ppm) - maximum 8-hour average concentration, not to be exceeded more than once per year.

(b) 40 milligrams per cubic meter (35 ppm) - maximum 1-hour concentration, not to be exceeded more than once per year.

(5) OZONE: PRIMARY AND SECONDARY STANDARDS. The primary and secondary standards for ozone are:

(a) 0.12 ppm (235 micrograms per cubic meter) - maximum 1-hour average concentration. The 1-hour ozone standards are attained when the expected number of days per calendar year with maximum hourly average concentrations above the designated level is equal to or less than one, as determined by the methodology of 40 CFR part 50, Appendix H, incorporated by reference in s. NR 484.04(4).

(b) 0.08 ppm - maximum 8-hour concentration. The 8-hour ozone standards are attained when the arithmetic mean of the fourth highest daily maximum 8-hour concentration at an ambient air quality monitoring site is less than or equal to 0.08 ppm, as determined by the methodology of 40 CFR part 50, Appendix I, incorporated by reference in s. NR 484.04(4m).

(c) 0.075 ppm - maximum 8-hour concentration. The 8-hour primary and secondary ozone ambient air quality standards are attained at an ambient air quality monitoring site when the 3-year average of the annual fourth-highest daily maximum 8-hour average ozone concentration is less than or equal to 0.075 ppm, as determined in accordance with 40 CFR part 50, Appendix P, incorporated by reference in s. NR 484.04(6t).

(d) 0.070 ppm - maximum 8-hour concentration. The 8-hour primary and secondary ozone ambient air quality standards are attained at an ambient air quality monitoring site when the 3-year average of the annual 4th-highest daily maximum 8-hour average ozone concentration is less than or equal to 0.070 ppm, as determined under 40 CFR part 50, Appendix U, incorporated by reference under s. NR 484.04(7s).

Note: The department promulgates ozone standards in response to federally promulgated ozone standards, and pursuant to its statutory obligation under s. 285.21(1) (a), Stats., pars. (a) and (b) reflect standards from 1979 and 1997. They are included here to conform to the federal standards in 40 CFR part 50, where they are also included.

(6) NITROGEN DIOXIDE.

(a) Primary standards. The primary standards for nitrogen dioxide are:
1. 0.053 ppm - primary annual average concentration. The primary annual standard is met when the annual average concentration in a calendar year is less than or equal to 0.053 ppm, as determined by the methodology of 40 CFR part 50, Appendix S, incorporated by reference in s. NR 484.04(7).

2. 0.100 ppm - primary 1-hour average concentration. The primary 1-hour standard is met when the 3-year average of the annual 98th percentile of the daily maximum 1-hour average concentration is less than or equal to 0.100 ppm, as determined by the methodology of 40 CFR part 50, Appendix S, incorporated by reference in s. NR 484.04(7).

(b) Secondary standard. The secondary standard for nitrogen dioxide is 0.053 ppm. The secondary standard is attained when the annual arithmetic mean concentration in a calendar year is less than or equal to 0.053 ppm, rounded to three decimal places. Fractional parts equal to or greater than 0.0005 ppm shall be rounded up. To demonstrate attainment, an annual mean shall be based upon hourly data that are at least 75% complete or upon data derived from manual methods that are at least 75% complete for the scheduled sampling days in each calendar quarter.

(7) LEAD: PRIMARY AND SECONDARY STANDARDS. The primary and secondary standards for lead and its compounds, measured as elemental lead, are the following:

(a) 1.5 micrograms per cubic meter, maximum arithmetic mean averaged over a calendar quarter, as a constituent of suspended particulate matter. The primary and secondary standards for lead and its compounds, measured as elemental lead are attained when the maximum arithmetic mean averaged over a calendar quarter is less than or equal to 1.5 micrograms per cubic meter, as determined in accordance with 40 CFR part 50, Appendix B, incorporated by reference in s. NR 484.04(3).

(b) 0.15 micrograms per cubic meter - maximum arithmetic mean. The primary and secondary ambient air quality standards for lead are attained when the maximum arithmetic 3-month mean concentration for a 3-year period is less than or equal to 0.15 micrograms per cubic meter, as determined in accordance with 40 CFR part 50, Appendix R, incorporated by reference in s. NR 484.04(6v).

(8) PM10: primary and secondary standards.

(a) The primary and secondary standards for PM 10 are 150 micrograms per cubic meter ( mg/m3) - maximum 24-hour average concentration.

(b) The PM10 standards are attained when the expected number of days per calendar year with a 24-hour average concentration above 150 mg/m3, the level designated in par. (a), is equal to or less than one.

(c) The expected concentrations and number of days shall be determined by the methodology contained in 40 CFR part 50, Appendix K, incorporated by reference in s. NR 484.04(6).

(9) PM2.5.

(am) Primary standards.
1. The primary standards for PM2.5 are 12.0 micrograms per cubic meter ( mg/m3) - annual arithmetic mean concentration and 35 mg/m 3 - 24-hour average concentration, measured in the ambient air as PM2.5 by either of the following methods:
a. A reference method based on 40 CFR part 50, Appendix L.

b. An equivalent method designated in accordance with s. NR 404.06(3) (b).

2. The primary annual standard is met when the annual arithmetic mean concentration, as determined in accordance with 40 CFR part 50, Appendix N, is less than or equal to 12.0 mg/m 3.

3. The primary 24-hour standard is met when the 98th percentile 24-hour concentration, as determined in accordance with 40 CFR part 50, Appendix N, is less than or equal to 35 mg/m 3.

(bm) Secondary standards.
1. The secondary standards for PM2.5 are 15.0 mg/m3 annual arithmetic mean concentration and 35 mg/m3 24-hour average concentration, measured in the ambient air as PM2.5 by either of the following methods:
a. A reference method based on 40 CFR part 50, Appendix L.

b. An equivalent method designated in accordance with s. NR 404.06(3) (b).

2. The secondary annual standard is met when the annual arithmetic mean concentration, as determined in accordance with 40 CFR part 50, Appendix N, is less than or equal to 15.0 mg/m3.

3. The secondary 24-hour standard is met when the 98th percentile 24-hour concentration, as determined in accordance with 40 CFR part 50, Appendix N, is less than or equal to 35 mg/m3.

40 CFR part 50, Appendices L and N are incorporated by reference in s. NR 484.04(6g) and (6r), respectively.

Disclaimer: These regulations may not be the most recent version. Wisconsin may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.