Air quality tool

Air Quality Lookup

Search any U.S. county and see its median AQI, EPA category, and good-day share in one step, then open the full profile for trends and pollutants.

According to the U.S. EPA Air Quality System, this lookup covers the 977 counties with an active monitor. Every figure is the county's latest reporting year. See the methodology for how the AQI is computed.

More ways to explore

Compare countiesPut counties side by side on AQI and good days. Cleanest counties finderFilter the cleanest counties by state. AQI health calculatorEnter an AQI to see the health guidance. Cleanest-air rankingsEvery county ranked by good-day share. Browse by stateState air-quality summaries and county lists. MethodologyHow the AQI and good-day share are built.

Frequently asked questions

What does the AQI lookup show?
Type any U.S. county or state name and the tool returns matching counties with their median Air Quality Index, the EPA category for that reading, the share of monitored days rated Good, and the worst single-day peak. Each result links to a full county profile with five-year trends and a pollutant breakdown.
What counts as a Good air day?
A Good day is any monitored day with an Air Quality Index of 50 or below, the cleanest band on the EPA scale. The percentage shown is the share of the year’s monitored days that fell in that band, so a county monitored for 360 days and a county monitored for 200 days compare on equal footing.
Why do some counties not appear?
The EPA only operates AQI monitors where population density, emissions sources, or attainment status warrant them, so roughly 2,200 U.S. counties have no monitor and cannot appear here. The lookup covers the 977 counties with at least one active monitor in the EPA Air Quality System.

Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.

Informational only, not professional advice. Data from EPA AQS. See our disclaimer.