Processed on 2024-03-04 12:51:54 PST.


Disclaimer: Data presented here come from a variety of sources and do not represent official EPA measurements. Please visit AirNow for official measurements.


Cumulative exposure to smoke is an important public health metric. This report summarizes the cumulative number of days air quality monitors in Colorado spent in each AQI category during the the month of April.

The tables below include only permanent monitors measuring PM2.5 and show cumulative exposure under existing NAAQS (National Ambient Air Quality Standards) and under the 2024 revised standards for PM2.5.

In the tables and plots below, ‘Old’ designates cumulative days calculated using the 2023 PM2.5 NAAQS while ‘New’ is calculated using the 2024 revised PM2.5 NAAQS. The impact of the NAAQS revision is quite clear.

April in Colorado

April 2014 – 19 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 276 2 0 0 0 0 63
New 267 11 0 0 0 0 63

April 2015 – 19 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 215 8 0 0 0 0 87
New 186 37 0 0 0 0 87

April 2016 – 30 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 298 1 0 0 0 0 42
New 286 13 0 0 0 0 42

April 2017 – 21 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 364 1 0 0 0 0 38
New 334 31 0 0 0 0 38

April 2018 – 41 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 385 13 0 0 0 0 36
New 337 61 0 0 0 0 36

April 2019 – 20 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 390 15 0 0 0 0 29
New 361 44 0 0 0 0 29

April 2020 – 39 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 409 12 0 0 0 0 44
New 390 31 0 0 0 0 44

April 2021 – 27 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 478 21 0 0 0 0 28
New 433 66 0 0 0 0 28

April 2022 – 34 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 454 20 0 0 0 0 22
New 381 93 0 0 0 0 22

April 2023 – 147 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 471 3 0 0 0 0 22
New 449 25 0 0 0 0 22