Air quality tools

Air Quality Tools

Four free, interactive tools built on EPA Air Quality System data, look up, compare, rank, and translate the air quality of any U.S. county.

977
Counties covered
4
Interactive tools
76.5%
US avg good days

One dataset, four ways in

Every tool here runs on the same EPA Air Quality System figures behind the county pages, no estimates, no fabrication, across all 977 monitored U.S. counties.

Look up
any county’s AQI & category
Compare
two or three counties side by side
Rank
cleanest counties by state
Translate
an AQI value into health guidance

Today’s cleanest is Lawrence County, Alabama (100.0% Good days); the most polluted, Harris County, Texas (8.8%).

How every EPA-monitored day across the U.S. distributes on the AQI scale, the national baseline your county is measured against.
All U.S. monitored counties AQI category distribution Stacked-segment bar showing the share of monitored days that fell in each EPA AQI category, Good, Moderate, USG, Unhealthy, Very Unhealthy, Hazardous, with median AQI marker. AQI category distribution 211,450 monitored days G M Median AQI 38.5 0 50 100 150 200 300 500 All U.S. monitored counties
  • Good · 157,710 d · 74.6%
  • Moderate · 51,698 d · 24.4%
  • USG · 1,640 d · 0.8%
  • Unhealthy · 319 d · 0.2%
  • Very Unhealthy · 40 d · 0.0%
  • Hazardous · 43 d · 0.0%

AQI Lookup

Search any U.S. county for its median AQI, EPA category, and good-day share.

County Compare

Put two or three counties side by side on the metrics that matter.

Cleanest Counties Finder

Rank the cleanest or most-polluted counties by state.

AQI Health Calculator

Enter an AQI value to see its category and EPA health guidance.

Cleanest county right now

Lawrence County, Alabama

100.0% good-air days, median AQI 23.

Most polluted county right now

Harris County, Texas

8.8% good-air days, median AQI 63.

Frequently asked questions

What can the PlainAir tools do?
The tools let you look up any county’s air quality, compare counties side by side, rank the cleanest or most-polluted counties by state, and translate any AQI value into plain-language health guidance. Each one runs on the same EPA Air Quality System data behind the rest of the site.
Is the data the same as the county pages?
Yes. Every tool queries the same EPA Air Quality System figures shown on the county, metro, and state profiles, so a value you find in a tool matches the full profile it links to. Nothing is estimated or fabricated.