Bad Air Days in Knox County, Tennessee: 2 a Year

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 520 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (74% particle days).

Which months to watch

Most bad days here fall in July and November 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 worst days on file

In 2000 to 2009 this county averaged 36 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2016, with 7 bad days on 366 monitored days.

Date	AQI	Main pollutant
2016-11-08	175	PM2.5
2016-11-14	160	PM2.5
2025-03-21	156	Ozone
2016-11-07	152	PM2.5
2021-04-06	150	PM2.5

An ordinary day in Knox

Across 3,647 monitored days from 2016 to 2025, the air in Knox County rated Good on 55% of them, less often than the 72% typical of monitored counties, and Moderate on 45%. The median day sat at AQI 48; one day in ten went above 64.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)69%2,527 days
ozone29%1,041 days
coarse dust (PM10)2%79 days

Knox County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	230	134	1	1	46	156
2024	366	205	160	1	0	48	105
2023	365	162	199	4	0	52	149
2022	365	185	180	0	0	49	77
2021	365	153	207	5	0	52	150
2020	366	233	133	0	0	44	91
2019	364	214	150	0	0	46	84
2018	364	186	177	1	0	50	112
2017	361	269	92	0	0	41	100
2016	366	167	192	7	3	52	175
2015	365	182	182	1	0	51	101
2014	362	144	218	0	0	53	84
2013	362	161	201	0	0	52	87
2012	265	158	90	17	3	46	217
2011	261	194	59	8	0	36	119
2010	322	209	100	13	0	44	133

*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.