Denver vs Fort Collins Air Quality Comparison
Which city has cleaner air right now, from the latest EPA AirNow AQI
As of September 16, 2026, Fort Collins, CO has cleaner air than Denver, CO — AQI 36 (Good) vs 43 (Good), a gap of 7 AQI points in the latest EPA AirNow observations. Lower AQI means cleaner air. Denver's reading is driven by O3 and Fort Collins's by O3.
Denver, CO
Good
Fort Collins, CO
Good
Summary
Fort Collins has 7 points better air quality
Fort Collins has an AQI of 36 compared to 43
Reduce Indoor Ozone in Denver
Today's main pollutant in Denver is ground-level ozone (AQI 43). Important: standard HEPA filters do NOT remove ozone — only a purifier with a substantial activated-carbon bed adsorbs it. The biggest wins are cutting indoor sources (gas appliances, certain "ionizer" purifiers) and ventilating when outdoor ozone is low (early morning). A high-carbon unit helps with the gases and VOCs that linger indoors.
Compare activated-carbon purifiers (for gases & ozone):
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