Regulations last checked for updates: Feb 07, 2026

Title 40 - Protection of Environment last revised: Dec 22, 2026
All TitlesTitle 40Chapter IPart 81Subpart C - Subpart C—Section 107 Attainment Status Designations
View all text of Subpart C [§ 81.300 - § 81.356]
§ 81.351 - Wyoming.

Wyoming—1971 Sulfur Dioxide NAAQS

[Primary and Secondary]

Designated area Does not meet primary standards Does not meet secondary standards Cannot be classified Better than national standards
Entire StateX

Wyoming—2010 Sulfur Dioxide NAAQS

[Primary]

Designated area 1 Designation
Date 2 Type
Albany CountyAttainment/Unclassifiable.
Big Horn CountyAttainment/Unclassifiable.
Campbell CountyAttainment/Unclassifiable.
Carbon County4/30/2021Attainment/Unclassifiable.
Converse County4/30/2021Attainment/Unclassifiable.
Crook CountyAttainment/Unclassifiable.
Fremont County (part)Attainment/Unclassifiable.
All areas west of the western border of Township 40North-Range 93West, T39N-R93W, and T38N-R93W, and south of U.S. Route 20.
Freemont County (remainder)4/30/2021Attainment/Unclassifiable.
Goshen CountyAttainment/Unclassifiable.
Hot Springs CountyAttainment/Unclassifiable.
Johnson CountyAttainment/Unclassifiable.
Lincoln CountyAttainment/Unclassifiable.
Natrona CountyAttainment/Unclassifiable.
Niobrara CountyAttainment/Unclassifiable.
Park CountyAttainment/Unclassifiable.
Platte CountyAttainment/Unclassifiable.
Sheridan CountyAttainment/Unclassifiable.
Sublette CountyAttainment/Unclassifiable.
Sweetwater County (part)Attainment/Unclassifiable.
All areas of the county east of U.S. Route 191.
Sweetwater County (remainder)4/30/2021Attainment/Unclassifiable.
Teton CountyAttainment/Unclassifiable.
Uinta CountyAttainment/Unclassifiable.
Washakie CountyAttainment/Unclassifiable.
Weston CountyAttainment/Unclassifiable.

1 Includes any Indian country in each county or area, unless otherwise specified. EPA is not determining the boundaries of any area of Indian country in this table, including any area of Indian country located in the larger designation area. The inclusion of any Indian country in the designation area is not a determination that the state has regulatory authority under the Clean Air Act for such Indian country.

2 This date is April 9, 2018, unless otherwise noted.

Wyoming—Carbon Monoxide

Designated Area Designation Classification
Date 1 Type Date 1 Type
StatewideUnclassifiable/Attainment
Albany County
Big Horn County
Campbell County
Carbon County
Converse County
Crook County
Fremont County
Goshen County
Hot Springs County
Johnson County
Laramie County
Lincoln County
Natrona County
Niobrara County
Park County
Platte County
Sheridan County
Sublette County
Sweetwater County
Teton County
Uinta County
Washakie County
Weston County

1 This date is November 15, 1990, unless otherwise noted.

Wyoming—Ozone (1-Hour Standard) 2

Designated area Designation Classification
Date 1 Type Date 1 Type
Statewide Unclassifiable/Attainment
Albany County
Big Horn County
Campbell County
Carbon County
Converse County
Crook County
Fremont County
Goshen County
Hot Springs County
Johnson County
Laramie County
Lincoln County
Natrona County
Niobrara County
Park County
Platte County
Sheridan County
Sublette County
Sweetwater County
Teton County
Uinta County
Washakie County
Weston County

1 This date is October 18, 2000, unless otherwise noted.

2 The 1-hour ozone standard is revoked effective June 15, 2005 for all areas in Wyoming.

Wyoming—PM-10

Designated Area Designation Classification
Date Type Date Type
Sheridan County:
City of Sheridan5/4/2018Attainment
Trona Industrial Area11/15/1990Unclassifiable
Campbell County (part)11/15/1990Unclassifiable
Converse County (part).
That area bounded by Township 40 through 52 North, and Ranges 69 through 73 West, inclusive of the Sixth Principal Meridian, Campbell and Converse Counties, excluding the areas defined as the Pacific Power and Light Area, the Hampshire Energy Area, and the Kennecott/Puron PSD Baseline Area—Powder River Basin.
Campbell County (part), That areabounded by NW1/4 of Section 27, T50N, R71W, Campbell County, Wyoming—Pacific Power and Light Area11/15/1990Unclassifiable
Campbell County (part), That area bounded by Section 6 excluding the SW 1/4; E 1/2 Section 7; Section 17 excluding the SW 1/4; Section 14 excluding the SE 1/4; Sections 2, 3, 4, 5, 8, 9, 10, 11, 15, 16 of T48N, R70W and Section 26 excluding the NE 1/4; SW 1/4 Section 23; Sections 19, 20, 21, 22, 27, 28, 29, 30, 31, 32, 33, 34, 35 of T49N, R70W.—Hampshire Energy Area11/15/1990Unclassifiable
Campbell County (part), That area described by the W 1/2SW 1/4 Section 18, W 1/2NW 1/4, NW 1/4SW 1/4 Section 19, T47N, R70W, S 1/2 Section 13, N 1/2, N 1/2SW 1/4, N 1/2SE 1/4 Section 24, T47N, R71W.—Kennecott/Puron PSD Baseline Area11/15/1990Unclassifiable
Rest of State 1 11/15/1990Unclassifiable

1 Denotes a single area designation for baseline area purposes.

Wyoming—1997 Annual PM2.5 NAAQS

[Primary and Secondary]

Designated area Designation a Classification
Date 1 Type Date Type
Casper, WY:
Natrona County (part)Unclassifiable/Attainment.
The portion within the City of Casper.
Cheyenne, WY:
Laramie County (part)Unclassifiable/Attainment.
The portion within the City of Cheyenne.
Evanston, WY:
Uinta County (part)Unclassifiable/Attainment.
The portion within the City of Evanston.
Gillette, WY:
Campbell County (part)Unclassifiable/Attainment.
The portion within the City of Gillette.
Jackson, WY:
Teton County (part)Unclassifiable/Attainment.
The portion within the City of Jackson.
Lander, WY:
Fremont County (part)Unclassifiable/Attainment.
The portion within the City of Lander.
Laramie, WY:
Albany County (part)Unclassifiable/Attainment.
The portion within the City of Laramie.
Riverton, WY:
Fremont County (part)Unclassifiable/Attainment.
The portion within the City of Riverton.
Rock Springs, WY:
Sweetwater County (part)Unclassifiable/Attainment.
The portion within the City of Rock Springs.
Sheridan, WY:
Sheridan County (part)Unclassifiable/Attainment.
The portion within the City of Sheridan.
Rest of State:
Albany County (remainder)Unclassifiable/Attainment.
Big Horn CountyUnclassifiable/Attainment.
Campbell CountyUnclassifiable/Attainment.
Carbon CountyUnclassifiable/Attainment.
Converse CountyUnclassifiable/Attainment.
Crook CountyUnclassifiable/Attainment.
Fremont County (remainder)Unclassifiable/Attainment.
Goshen CountyUnclassifiable/Attainment.
Hot Springs CountyUnclassifiable/Attainment.
Johnson CountyUnclassifiable/Attainment.
Laramie County (remainder)Unclassifiable/Attainment.
Lincoln CountyUnclassifiable/Attainment.
Natrona County (remainder)Unclassifiable/Attainment.
Niobrara CountyUnclassifiable/Attainment.
Park CountyUnclassifiable/Attainment.
Platte CountyUnclassifiable/Attainment.
Sheridan County (remainder)Unclassifiable/Attainment.
Sublette CountyUnclassifiable/Attainment.
Sweetwater CountyUnclassifiable/Attainment.
Teton County (remainder)Unclassifiable/Attainment.
Uinta County (remainder)Unclassifiable/Attainment.
Washakie CountyUnclassifiable/Attainment.
Weston CountyUnclassifiable/Attainment.

a Includes Indian Country located in each county or area, except as otherwise specified.

1 This date is 90 days after January 5, 2005, unless otherwise noted.

Wyoming—2012 Annual PM2.5 NAAQS

[Primary]

Designated area 1 Designation Classification
Date 2 Type Date 2 Type
Statewide:
Albany CountyUnclassifiable/Attainment
Big Horn CountyUnclassifiable/Attainment
Campbell CountyUnclassifiable/Attainment
Carbon CountyUnclassifiable/Attainment
Converse CountyUnclassifiable/Attainment
Crook CountyUnclassifiable/Attainment
Fremont CountyUnclassifiable/Attainment
Goshen CountyUnclassifiable/Attainment
Hot Springs CountyUnclassifiable/Attainment
Johnson CountyUnclassifiable/Attainment
Laramie CountyUnclassifiable/Attainment
Lincoln CountyUnclassifiable/Attainment
Natrona CountyUnclassifiable/Attainment
Niobrara CountyUnclassifiable/Attainment
Park CountyUnclassifiable/Attainment
Platte CountyUnclassifiable/Attainment
Sheridan CountyUnclassifiable/Attainment
Sublette CountyUnclassifiable/Attainment
Sweetwater CountyUnclassifiable/Attainment
Teton CountyUnclassifiable/Attainment
Uinta CountyUnclassifiable/Attainment
Washakie CountyUnclassifiable/Attainment
Weston CountyUnclassifiable/Attainment

1 Includes areas of Indian country located in each county or area, except as otherwise specified.

2 This date is April 15, 2015, unless otherwise noted.

Wyoming—1997 24-Hour PM2.5 NAAQS

[Primary and Secondary]

Designated area Designation a Classification
Date 1 Type Date Type
Casper, WY:
Natrona County (part)Unclassifiable/Attainment
The portion within the City of Casper.
Cheyenne, WY:
Laramie County (part)Unclassifiable/Attainment
The portion within the City of Cheyenne.
Evanston, WY:
Uinta County (part)Unclassifiable/Attainment
The portion within the City of Evanston.
Gillette, WY:
Campbell County (part)Unclassifiable/Attainment
The portion within the City of Gillette.
Jackson, WY:
Teton County (part)Unclassifiable/Attainment
The portion within the City of Jackson.
Lander, WY:
Fremont County (part)Unclassifiable/Attainment
The portion within the City of Lander.
Laramie, WY:
Albany County (part)Unclassifiable/Attainment
The portion within the City of Laramie.
Riverton, WY:
Fremont County (part)Unclassifiable/Attainment
The portion within the City of Riverton.
Rock Springs, WY:
Sweetwater County (part)Unclassifiable/Attainment
The portion within the City of Rock Springs.
Sheridan, WY:
Sheridan County (part)Unclassifiable/Attainment
The portion within the City of Sheridan.
Rest of State:
Albany County (remainder)Unclassifiable/Attainment
Big Horn CountyUnclassifiable/Attainment
Campbell CountyUnclassifiable/Attainment
Carbon CountyUnclassifiable/Attainment
Converse CountyUnclassifiable/Attainment
Crook CountyUnclassifiable/Attainment
Fremont County (remainder)Unclassifiable/Attainment
Goshen CountyUnclassifiable/Attainment
Hot Springs CountyUnclassifiable/Attainment
Johnson CountyUnclassifiable/Attainment
Laramie County (remainder)Unclassifiable/Attainment
Lincoln CountyUnclassifiable/Attainment
Natrona County (remainder)Unclassifiable/Attainment
Niobrara CountyUnclassifiable/Attainment
Park CountyUnclassifiable/Attainment
Platte CountyUnclassifiable/Attainment
Sheridan County (remainder)Unclassifiable/Attainment
Sublette CountyUnclassifiable/Attainment
Sweetwater CountyUnclassifiable/Attainment
Teton County (remainder)Unclassifiable/Attainment
Uinta County (remainder)Unclassifiable/Attainment
Washakie CountyUnclassifiable/Attainment
Weston CountyUnclassifiable/Attainment

a Includes Indian Country located in each county or area, except as otherwise specified.

1 This date is 90 days after January 5, 2005, unless otherwise noted.

Wyoming—2006 24-Hour PM2.5 NAAQS

[Primary and Secondary]

Designated area Designation a Classification
Date 1 Type Date Type
Casper, WY:
Natrona County (part)Unclassifiable/Attainment
The portion within the City of Casper.
Cheyenne, WY:
Laramie County (part)Unclassifiable/Attainment
The portion within the City of Cheyenne.
Evanston, WY:
Uinta County (part)Unclassifiable/Attainment
The portion within the City of Evanston.
Gillette, WY:
Campbell County (part)Unclassifiable/Attainment
The portion within the City of Gillette.
Jackson, WY:
Teton County (part)Unclassifiable/Attainment
The portion within the City of Jackson.
Lander, WY:
Fremont County (part)Unclassifiable/Attainment
The portion within the City of Lander.
Laramie, WY:
Albany County (part)Unclassifiable/Attainment
The portion within the City of Laramie.
Riverton, WY:
Fremont County (part)Unclassifiable/Attainment
The portion within the City of Riverton.
Rock Springs, WY:
Sweetwater County (part)Unclassifiable/Attainment
The portion within the City of Rock Springs.
Sheridan, WY:
Sheridan County (part)Unclassifiable/Attainment
The portion within the City of Sheridan.
Rest of State:
Albany County (remainder)Unclassifiable/Attainment
Big Horn CountyUnclassifiable/Attainment
Campbell CountyUnclassifiable/Attainment
Carbon CountyUnclassifiable/Attainment
Converse CountyUnclassifiable/Attainment
Crook CountyUnclassifiable/Attainment
Fremont County (remainder)Unclassifiable/Attainment
Goshen CountyUnclassifiable/Attainment
Hot Springs CountyUnclassifiable/Attainment
Johnson CountyUnclassifiable/Attainment
Laramie County (remainder)Unclassifiable/Attainment
Lincoln CountyUnclassifiable/Attainment
Natrona County (remainder)Unclassifiable/Attainment
Niobrara CountyUnclassifiable/Attainment
Park CountyUnclassifiable/Attainment
Platte CountyUnclassifiable/Attainment
Sheridan County (remainder)Unclassifiable/Attainment
Sublette CountyUnclassifiable/Attainment
Sweetwater CountyUnclassifiable/Attainment
Teton County (remainder)Unclassifiable/Attainment
Uinta County (remainder)Unclassifiable/Attainment.
Washakie CountyUnclassifiable/Attainment
Weston CountyUnclassifiable/Attainment

a Includes Indian Country located in each county or area, except as otherwise specified.

1 This date is 30 days after November 13, 2009, unless otherwise noted.

Wyoming—NO2 (1971 Annual Standard)

Designated area Does not meet primary standards Cannot be classified or better than national standards
Entire StateX

Wyoming—NO2 (2010 1-Hour Standard)

Designated area Designation a
Date 1 Type
Albany CountyUnclassifiable/Attainment.
Big Horn CountyUnclassifiable/Attainment.
Campbell CountyUnclassifiable/Attainment.
Carbon CountyUnclassifiable/Attainment.
Converse CountyUnclassifiable/Attainment.
Crook CountyUnclassifiable/Attainment.
Fremont CountyUnclassifiable/Attainment.
Goshen CountyUnclassifiable/Attainment.
Hot Springs CountyUnclassifiable/Attainment.
Johnson CountyUnclassifiable/Attainment.
Laramie CountyUnclassifiable/Attainment.
Lincoln CountyUnclassifiable/Attainment.
Natrona CountyUnclassifiable/Attainment.
Niobrara CountyUnclassifiable/Attainment.
Park CountyUnclassifiable/Attainment.
Platte CountyUnclassifiable/Attainment.
Sheridan CountyUnclassifiable/Attainment.
Sublette CountyUnclassifiable/Attainment.
Sweetwater CountyUnclassifiable/Attainment.
Teton CountyUnclassifiable/Attainment.
Uinta CountyUnclassifiable/Attainment.
Washakie CountyUnclassifiable/Attainment.
Weston CountyUnclassifiable/Attainment.

a Includes Indian Country located in each county or area, except as otherwise specified.

1 This date is 90 days after October 31, 2011, unless otherwise noted.

Wyoming—1997 8-Hour Ozone NAAQS

[Primary and Secondary]

Designated area Designation a Category/classification
Date 1 Type Date 1 Type
StatewideUnclassifiable/Attainment
Albany CountyUnclassifiable/Attainment
Big Horn CountyUnclassifiable/Attainment
Campbell CountyUnclassifiable/Attainment
Carbon CountyUnclassifiable/Attainment
Converse CountyUnclassifiable/Attainment
Crook CountyUnclassifiable/Attainment
Fremont CountyUnclassifiable/Attainment
Goshen CountyUnclassifiable/Attainment
Hot Springs CountyUnclassifiable/Attainment
Johnson CountyUnclassifiable/Attainment
Laramie CountyUnclassifiable/Attainment
Lincoln CountyUnclassifiable/Attainment
Natrona CountyUnclassifiable/Attainment
Niobrara CountyUnclassifiable/Attainment
Park CountyUnclassifiable/Attainment
Platte CountyUnclassifiable/Attainment
Sheridan CountyUnclassifiable/Attainment
Sublette CountyUnclassifiable/Attainment
Sweetwater CountyUnclassifiable/Attainment
Teton CountyUnclassifiable/Attainment
Uinta CountyUnclassifiable/Attainment
Washakie CountyUnclassifiable/Attainment
Weston CountyUnclassifiable/Attainment

a Includes Indian Country located in each county or area, except as otherwise specified.

1 This date is June 15, 2004, unless otherwise noted.

Wyoming—2008 8-Hour Ozone NAAQS

[Primary and Secondary]

Designated area Designation Classification
Date 1 Type Date 1 Type
Upper Green River Basin Area, WY: 2NonattainmentMarginal.
Lincoln County (part)
The area of the county north and east of the boundary defined by a line starting at the point defined by the intersection of the southwest corner Section 30 Range (R) 115 West Township (T) 27N and the northwest corner of Section 31 R 115 West T27N of Sublette County at Sublette County's border with Lincoln County. From this point the boundary moves to the west 500 feet to Aspen Creek. The boundary follows the centerline of Aspen Creek downstream to the confluence of Aspen Creek and Fontenelle Creek (in R116W T26N, Section 1). From this point the boundary moves generally to the south along the centerline of Fontenelle Creek to the confluence of Fontenelle Creek and Roney Creek (in R115W T24N Section 6). From the confluence, the boundary moves generally to the east along the centerline of Fontenelle Creek and into the Fontenelle Reservoir (in R112W T24N Section 6). The boundary moves east southeast along the centerline of the Fontenelle Reservoir and then toward the south along the centerline of the Green River to where the Green River in R111W T24N Section 31 crosses into Sweetwater County.
Sublette County
Sweetwater County (part)
The area of the county west and north of the boundary which begins at the midpoint of the Green River, where the Green River enters Sweetwater County from Lincoln County in R111W T24N Section 31. From this point, the boundary follows the center of the channel of the Green River generally to the south and east to the confluence of the Green River and the Big Sandy River (in R109W T22N Section 28). From this point, the boundary moves generally north and east along the centerline of the Big Sandy River to the confluence of the Big Sandy River with Little Sandy Creek (in R106W T25N Section 33). The boundary continues generally toward the northeast along the centerline of Little Sandy Creek to the confluence of Little Sandy Creek and Pacific Creek (in R106W T25N Section 24). From this point, the boundary moves generally to the east and north along the centerline of Pacific Creek to the confluence of Pacific Creek and Whitehorse Creek (in R103W T26N Section 10). From this point the boundary follows the centerline of Whitehorse Creek generally to the northeast until it reaches the eastern boundary of Section 1 R103W T26N. From the point where Whitehorse Creek crosses the eastern section line of Section 1 R103W T26N, the boundary moves straight north along the section line to the southeast corner of Section 36 R103W T27N in Sublette County where the boundary ends.
Rest of State and Rest of Indian CountryUnclassifiable/Attainment

1 This date is July 20, 2012, unless otherwise noted.

2 Excludes Indian country located in each area, unless otherwise noted.

Wyoming—2015 8-Hour Ozone NAAQS

[Primary and Secondary]

Designated area 1 Designation Classification
Date 2 Type Date 2 Type
Albany CountyAttainment/Unclassifiable
Big Horn County1/16/2018Attainment/Unclassifiable
Campbell County1/16/2018Attainment/Unclassifiable
Carbon County1/16/2018Attainment/Unclassifiable
Converse County1/16/2018Attainment/Unclassifiable
Crook County1/16/2018Attainment/Unclassifiable
Fremont County1/16/2018Attainment/Unclassifiable
Goshen County1/16/2018Attainment/Unclassifiable
Hot Springs County1/16/2018Attainment/Unclassifiable
Johnson County1/16/2018Attainment/Unclassifiable
Laramie CountyAttainment/Unclassifiable
Lincoln County1/16/2018Attainment/Unclassifiable
Natrona County1/16/2018Attainment/Unclassifiable
Niobrara County1/16/2018Attainment/Unclassifiable
Park County1/16/2018Attainment/Unclassifiable
Platte County1/16/2018Attainment/Unclassifiable
Sheridan County1/16/2018Attainment/Unclassifiable
Sublette County1/16/2018Attainment/Unclassifiable
Sweetwater County1/16/2018Attainment/Unclassifiable
Teton County1/16/2018Attainment/Unclassifiable
Uinta County1/16/2018Attainment/Unclassifiable
Washakie County1/16/2018Attainment/Unclassifiable
Weston County1/16/2018Attainment/Unclassifiable

1 Includes any Indian country in each county or area, unless otherwise specified. EPA is not determining the boundaries of any area of Indian country in this table, including any area of Indian country located in the larger designation area. The inclusion of any Indian country in the designation area is not a determination that the state has regulatory authority under the Clean Air Act for such Indian country.

2 This date is August 3, 2018, unless otherwise noted.

Wyoming—2008 Lead NAAQS

Designated area Designation for the 2008 NAAQS a
Date 1 Type
Whole StateUnclassifiable/Attainment.

a Includes Indian Country located in each county or area, except as otherwise specified.

1 December 31, 2011 unless otherwise noted.

[43 FR 8964, Mar. 3, 1978] Editorial Note:For Federal Register citations affecting § 81.351, see the List of CFR Sections Affected, which appears in the Finding Aids section of the printed volume and at www.govinfo.gov.
authority: 42 U.S.C. 7401,
source: 36 FR 22421, Nov. 25, 1971, unless otherwise noted.
cite as: 40 CFR 81.351
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