Bad Air Days in DeKalb County, Tennessee: 0 a Year

0 bad air days a year

Rare: among the cleanest-air counties EPA monitors. Ranked 984 of 996 monitored counties, where 1 is worst.

What actually helps here

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.

Better or worse than it was

In 2000 to 2009 this county averaged 7 bad days a year; in 2016 to 2025, 0. The air has improved.

Date	AQI	Main pollutant
2022-03-04	100	Ozone
2023-04-20	90	Ozone
2018-06-06	87	Ozone
2023-06-16	87	Ozone
2016-04-20	84	Ozone

An ordinary day in DeKalb

Across 3,533 monitored days from 2016 to 2025, the air in DeKalb County rated Good on 95% of them, more often than the 72% typical of monitored counties, and Moderate on 5%. The median day sat at AQI 36; one day in ten went above 47.

The pollutant setting the AQI on an ordinary day here:

ozone100%3,533 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	357	345	12	0	0	34	84
2024	336	312	24	0	0	38	77
2023	352	333	19	0	0	37	90
2022	359	348	11	0	0	35	100
2021	363	349	14	0	0	35	84
2020	341	336	5	0	0	33	61
2019	363	335	28	0	0	37	80
2018	348	331	17	0	0	33	87
2017	363	349	14	0	0	36	84
2016	351	330	21	0	0	37	84
2015	353	336	17	0	0	35	77
2014	359	340	19	0	0	35	84
2013	346	332	14	0	0	36	97
2012	313	269	39	5	1	39	172
2011	350	314	36	0	0	38	84
2010	350	297	48	5	0	38	119

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

Elsewhere in Tennessee

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.