The Air Quality Index (AQI) tells you how clean or polluted your outdoor air is and the associated health effects that may be of concern.

The U.S. Air Quality Index (AQI) is EPA's tool for communicating about outdoor air quality and health. The AQI includes six color-coded categories, each corresponding to a range of index values.

What it is: The U.S. Air Quality Index, or AQI, is EPA’s tool for communicating daily air quality. It uses color-coded categories and provides statements for each category that tell you about air quality in your area, which groups of people may be affected, and steps you can take to reduce your exposure to air pollution.

AirNow is your one-stop source for air quality data. Our recently redesigned site highlights air quality in your local area first, while still providing air quality information at state, national, and world views.

The list below shows the areas with the highest NowCast AQI for the current hour. The AirNow system automatically generates this list every hour, based on the areas with the highest NowCast AQI for ozone or particle pollution.

Local air quality can affect our daily lives. Like the weather, it can change from day to day. EPA developed the Air Quality Index, or AQI, to make information available about the health effects of the five most common air pollutants, and how to avoid those effects.

El AQI incluye seis categorías codificadas por colores, cada una corresponde a un rango de los valores del índice. Cuanto más alto es el valor del AQI, mayor es el nivel de contaminación atmosférica y mayor la preocupación para la salud.

The Air Quality Index uses numbers from 0 to 500. These numbers are used to decide the AQI color. On days measuring less than 100, the air is clean. If the air is dirtier, the numbers get bigger. On days measuring more than 100, the air can be bad for you to breathe. Here is how the AQI numbers match up with the AQI colors:

This chart shows the daily AQI in your area for each of the last 7 days. Mouse over or tap a bar to see which pollutant (ozone or PM) was highest that day.

AirNow reports air quality using the official U.S. Air Quality Index (AQI), a color-coded index designed to communicate whether air quality is healthy or unhealthy for you. When you know the AQI in your area, you can take steps to protect your health.