Carbon County, Wyoming air quality history

Daily Air Quality Index summaries from EPA monitors in Carbon, Wyoming, 1994–2025.

100%

Good days in 2025

Median daily AQI, 2025

Days above 100 in 2025

362

Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Carbon, Wyoming on 362 days. 362 of those days (100%) were in the Good range, and the median daily AQI was 8. That median is lower than the typical monitored county in Wyoming (median 41 across 17 counties), and lower than the typical monitored U.S. county (40). The main pollutant was nitrogen dioxide (NO₂) on 321 days. Across the years with fuller monitoring, the share of Good days rose: an average of 89% in 1997–2008 versus 100% in 2023–2025.

Years with fewer than 120 monitored days (1999, 2000, 2001, 2002, 2003, 2007…) are shown in the table but left out of comparisons and trend statements.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Good
Moderate
Unhealthy for Sensitive Groups
Unhealthy
Very Unhealthy
Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median daily AQI
90th-percentile daily AQI

Main pollutant by day, 2025

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

Pollutant	Days as main pollutant	Share of monitored days
Nitrogen dioxide (NO₂)	321	89%
Ozone	39	11%
Fine particles (PM2.5)	2	1%

Year-by-year data

Annual AQI summary by year
Year	Days with AQI	Good	Moderate	Unhealthy for Sensitive Groups	Very Unhealthy	Hazardous	Median AQI	90th pct.	Max AQI	Main pollutant
2025	362	362	0	0	0	0	8	33	43	NO2
2024	356	356	0	0	0	0	8	18	35	NO2
2023	362	362	0	0	0	0	8	20	33	NO2
2022	361	361	0	0	0	0	9	18	27	NO2
2021	348	348	0	0	0	0	10	20	37	NO2
2020	304	304	0	0	0	0	8	21	31	NO2
2019	364	325	38	1	0	0	43	51	112	Ozone
2018	365	292	73	0	0	0	42	61	90	Ozone
2017	365	311	54	0	0	0	43	54	80	Ozone
2016	366	335	31	0	0	0	42	50	84	Ozone
2015	365	326	38	1	0	0	42	51	105	Ozone
2014	365	327	38	0	0	0	42	51	80	Ozone
2013	360	347	13	0	0	0	38	46	71	Ozone
2012	354	270	84	0	0	0	43	61	97	Ozone
2011	358	279	79	0	0	0	44	61	80	Ozone
2010	349	264	84	1	0	0	45	64	112	Ozone
2009	161	159	2	0	0	0	35	43	55	Ozone
2008	283	210	71	2	0	0	44	67	126	Ozone
2007	82	82	0	0	0	0	37	42	46	Ozone
2003	46	42	3	1	0	0	19	50	107	PM10
2002	67	59	6	2	0	0	22	54	148	PM10
2001	61	58	3	0	0	0	19	37	57	PM10
2000	60	57	3	0	0	0	17	46	88	PM10
1999	60	50	6	0	2	2	23	64	544	PM10
1998	180	175	3	1	0	1	6	27	359	PM10
1997	181	173	7	1	0	0	8	27	120	PM10
1996	61	51	9	1	0	0	19	59	102	PM10
1995	56	46	9	1	0	0	19	65	102	PM10
1994	49	47	2	0	0	0	16	32	76	PM10

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

Counties in Wyoming with a similar median AQI in 2025

All monitored counties in Wyoming

Source: U.S. EPA AirData, “Annual AQI by County” files for 1994–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem