Processed on 2024-03-04 12:52:03 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 May.

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.

May in Colorado

May 2014 – 19 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 304 13 0 0 0 0 35
New 270 47 0 0 0 0 35

May 2015 – 19 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 259 4 0 0 0 0 57
New 243 20 0 0 0 0 57

May 2016 – 30 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 293 8 0 0 0 0 51
New 263 38 0 0 0 0 51

May 2017 – 21 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 374 3 1 0 0 0 38
New 370 7 1 0 0 0 38

May 2018 – 41 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 411 5 0 0 0 0 32
New 388 28 0 0 0 0 32

May 2019 – 20 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 406 9 0 0 0 0 33
New 381 34 0 0 0 0 33

May 2020 – 39 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 416 11 0 0 0 0 53
New 397 30 0 0 0 0 53

May 2021 – 27 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 509 17 0 0 0 0 18
New 475 51 0 0 0 0 18

May 2022 – 34 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 463 9 0 0 0 0 40
New 432 40 0 0 0 0 40

May 2023 – 147 permanent monitors

Good Moderate USG Unhealthy Very Unhealthy Hazardous Missing
Old 419 56 8 16 0 0 45
New 392 81 10 16 0 0 45