Daily Air Quality Index summaries from EPA monitors in Knox, Indiana, 1984–2025.
91%
Good days in 2025
36
Median daily AQI, 2025
0
Days above 100 in 2025
344
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Knox, Indiana on 344 days. 314 of those days (91%) were in the Good range, and the median daily AQI was 36. That median is lower than the typical monitored county in Indiana (median 41 across 33 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 344 days. Across the years with fuller monitoring, the share of Good days rose: an average of 53% in 1984–1986 versus 88% in 2023–2025.
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
Ozone
344
100%
Year-by-year data
Annual AQI summary by year
Year
Days with AQI
Good
Moderate
Unhealthy for Sensitive Groups
Unhealthy
Very Unhealthy
Hazardous
Median AQI
90th pct.
Max AQI
Main pollutant
2025
344
314
30
0
0
0
0
36
49
93
Ozone
2024
360
314
46
0
0
0
0
38
54
90
Ozone
2023
364
313
43
8
0
0
0
39
58
126
Ozone
2022
344
321
23
0
0
0
0
36
48
87
Ozone
2021
360
320
38
2
0
0
0
36
51
108
Ozone
2020
351
328
22
1
0
0
0
33
48
105
Ozone
2019
359
328
31
0
0
0
0
36
50
87
Ozone
2018
357
311
42
4
0
0
0
35
54
122
Ozone
2017
355
323
32
0
0
0
0
36
50
100
Ozone
2016
359
313
42
4
0
0
0
35
61
119
Ozone
2015
349
314
35
0
0
0
0
34
51
93
Ozone
2014
348
313
35
0
0
0
0
34
51
90
Ozone
2013
350
318
32
0
0
0
0
36
50
90
Ozone
2012
351
263
63
25
0
0
0
39
87
136
Ozone
2011
353
236
111
4
2
0
0
44
70
154
Ozone
2010
362
252
106
4
0
0
0
42
72
112
Ozone
2009
357
258
97
2
0
0
0
39
62
112
Ozone
2008
364
255
107
2
0
0
0
42
69
108
Ozone
2007
363
220
118
25
0
0
0
45
90
150
Ozone
2006
362
233
122
7
0
0
0
41
78
147
Ozone
2005
351
216
113
22
0
0
0
44
84
140
Ozone
2004
360
246
112
2
0
0
0
41
69
112
Ozone
2003
363
233
115
14
1
0
0
43
84
164
Ozone
2002
358
224
102
22
10
0
0
42
100
174
Ozone
2001
363
224
115
23
1
0
0
44
87
154
Ozone
2000
358
242
104
10
2
0
0
43
77
154
Ozone
1999
350
249
61
33
7
0
0
41
108
177
Ozone
1998
356
244
82
25
5
0
0
39
97
200
Ozone
1997
363
286
59
16
2
0
0
36
84
156
Ozone
1996
358
257
72
24
5
0
0
38
90
177
Ozone
1995
349
240
77
28
4
0
0
38
93
166
Ozone
1994
360
257
72
23
8
0
0
38
97
174
Ozone
1993
361
285
67
6
3
0
0
35
77
159
Ozone
1992
358
293
50
12
3
0
0
36
80
166
Ozone
1991
361
261
69
22
9
0
0
37
93
182
Ozone
1990
359
270
57
25
7
0
0
38
97
187
Ozone
1989
224
134
64
23
3
0
0
46
101
187
Ozone
1988
313
178
77
35
23
0
0
46
133
187
Ozone
1987
331
201
78
44
8
0
0
43
112
177
Ozone
1986
246
140
74
26
6
0
0
48
105
185
Ozone
1985
215
133
53
24
5
0
0
44
105
174
Ozone
1984
128
51
38
29
9
1
0
74
147
204
Ozone
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 Indiana with a similar median AQI in 2025
