Bad Air Days in Carbon County, Utah: 2 a Year

2 bad air days a year

About the middle of monitored US counties. Ranked 485 of 996 monitored counties, where 1 is worst.

What makes them bad: a mix of particles and ozone (48% particle days).

Which months to watch

Most bad days here fall in August and July and June. Averaged over 2016 to 2025.

What to buy, and what not to

Bad air days are rare here. A standard furnace filter is enough; no purifier needed for outdoor air.
On the odd bad day, check AirNow and keep windows shut.

The record for Carbon

The worst recent year was 2021, with 12 bad days on 365 monitored days.

Date	AQI	Main pollutant
2021-08-07	155	PM2.5
2021-08-10	151	PM2.5
2021-08-29	146	PM2.5
2021-08-06	143	PM2.5
2021-08-09	132	PM2.5

Most days, not the worst ones

Across 3,577 monitored days from 2016 to 2025, the air in Carbon County rated Good on 77% of them, more often than the 72% typical of monitored counties, and Moderate on 22%. The median day sat at AQI 44; one day in ten went above 63.

The pollutant setting the AQI on an ordinary day here:

ozone95%3,400 days
fine particles (PM2.5)3%120 days
nitrogen dioxide2%57 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	364	263	99	2	0	44	108
2024	366	278	87	1	0	44	112
2023	363	329	34	0	0	42	70
2022	364	321	43	0	0	43	74
2021	365	265	88	12	2	44	155
2020	350	308	42	0	0	43	93
2019	365	265	99	1	0	46	108
2018	364	231	128	5	0	46	115
2017	364	262	102	0	0	45	90
2016	312	230	82	0	0	44	93
2015	293	200	91	2	0	46	112
2014	365	281	84	0	0	44	87
2013	362	252	108	2	0	44	115
2012	365	231	126	8	0	45	119
2011	272	158	113	1	0	49	108

*2025 may be a partial year in EPA's file.

Nearby counties on file

How this is counted

A bad air day is a day the county's daily AQI from EPA AirData went above 100, the level where EPA tells children, older adults and people with asthma or heart disease to cut back outdoors. Monitors do not run every day, so yearly counts are scaled to 365 days. This is the record, not today's air: for that, check AirNow. More on the method in how the county numbers are made, on the AQI 100 line in what counts as a bad air day, and on why a purifier does not touch ozone in smoke vs ozone.