Air Quality Alert: Denver-Boulder Air Quality Reaches Unhealthy for Sensitive Groups Level

Source: EPA · Denver-Boulder, CO

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On February 23, 2026, the Denver-Boulder area recorded an AQI of 104, categorized as Unhealthy for Sensitive Groups, with PM10 identified as the primary pollutant.

What this EPA air-quality advisory tells you, and what most readers miss

This notice was issued by EPA on February 24, 2026 and geographically references Denver-Boulder, CO. Its severity classification of "low" signals how the issuing agency weighs the risk of harm if no action is taken — "critical" and "high" tier alerts typically carry direct consumer actions, while "medium" and "low" tend toward informational guidance or monitoring advisories. The category it belongs to — Air Quality — determines the regulatory framework behind it, which shapes what remedies (refunds, replacements, recalls, evacuations) are available to affected individuals and who holds statutory responsibility for enforcement.

Most readers skim a notice like this, check whether they are personally affected, and move on. The more useful lens is to read it as a data point about the issuing system: how quickly EPA detected the hazard, how precise the geographic or product-identifier scope is, and whether similar notices have clustered in the same category or region in the last 90 days. Cluster patterns frequently precede a broader regulatory action — a single localized EPA air-quality advisory is isolated; three of them within a quarter often indicate a supply-chain, infrastructure, or seasonal driver that will keep producing notices until something structural changes.

For decision-making, Areazine pairs each alert with the original agency URL, the full agency name, and a timestamp so you can verify the notice against the primary source before acting on it. Tags on this item (air-quality, epa, aqi, Denver-Boulder) map to related alerts in the same area of risk — browsing them together gives a clearer picture than any single notice alone, because the shape of an ongoing issue only becomes visible across multiple sequential alerts.

Current Air Quality

In the Denver-Boulder, CO reporting area, the air quality index (AQI) reached a peak of 104 on February 23, 2026. The primary pollutant of concern is PM10, which is currently in the "Unhealthy for Sensitive Groups" category. Other measured pollutants include PM2.5 at an AQI of 78 (Moderate) and Ozone (O3) at an AQI of 45 (Good).

What This Means

An AQI of 104 falls into the "Unhealthy for Sensitive Groups" category. According to standard EPA guidance, this level indicates that air quality is unhealthy for certain groups of people, while the general public is unlikely to be affected.

Who Should Take Precautions

Groups at risk include people with heart or lung disease, older adults, and children. These individuals are more likely to be affected by the presence of PM10 in the air.

What You Should Do

Members of sensitive groups should consider reducing prolonged or heavy exertion outdoors. The general public does not need to take special precautions and can continue with normal outdoor activities.

Source

EPA AirNow

Original source: EPA Official Notice ↗

All Air Quality →

Frequently Asked Questions

Common questions about this EPA air-quality advisory.

What is this EPA air-quality advisory about?
On February 23, 2026, the Denver-Boulder area recorded an AQI of 104, categorized as Unhealthy for Sensitive Groups, with PM10 identified as the primary pollutant.
Which agency issued this alert?
This alert was issued by EPA. The original notice is available at the source link at the bottom of this article.
How severe is this alert?
This alert is classified as "low" severity. No immediate action required, but stay aware.
What area is affected?
This alert affects Denver-Boulder, CO. Check with EPA for the most current geographic scope.
Where can I find more Air Quality updates?
Browse the full Air Quality feed on Areazine at areazine.com/air-quality/ for the latest updates from EPA and other agencies.