Basic Information

The Air Quality Index

The Air Quality Index (AQI) is an index for reporting daily air quality. It tells you how clean or polluted your outdoor air is, and what associated health effects might be a concern for you. The AQI focuses on health effects you may experience within a few hours or days after breathing polluted air. EPA calculates the AQI for five major air pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution (also known as particulate matter), carbon monoxide, sulfur dioxide, and nitrogen dioxide. For each of these pollutants, EPA has established national air quality standards to protect public health. For Information regarding indoor air quality please visit the Indoor Air Quality website.

The AIRNOW Web site

The U.S. EPA has developed the AIRNow website to provide the public with easy access to national air quality information. The website offers daily AQI forecasts as well as real-time AQI conditions for over 275 cities across the US, and provides links to more detailed State and local air quality websites.

This website

• presents comprehensive air quality maps and forecasts

• supplies real-time images of air quality and visibility via webcams

• displays air quality forecasts (good, moderate, unhealthy for sensitive groups, unhealthy, very unhealthy, hazardous) for "air action days" in major metropolitan areas around the country

• provides suggestions on what you can do to help improve the air quality where you live.

Where You Live - Direct access to current AQI conditions (air quality maps and animations), AQI forecasts and website links to state and local information.

Air Quality Forecasts - Nationwide daily air quality forecasts provided by State and Local Air Agencies for over 275 major US cities.

Air Quality Conditions - Nationwide and regional real-time ozone air quality maps covering 44 US States and parts of Canada. These maps are updated daily every hour.

Publications - documentation on the Air Quality Index (AQI), air pollution health effects, and more.

About the Data
The air quality data used in these maps and to generate forecasts are collected using either Federal reference or equivalent monitoring techniques or techniques approved by the State Local or Tribal monitoring agencies. Since the information needed to make maps must be as "real-time" as possible, the data are displayed as soon as practical after the end of each hour. Although some preliminary data quality assessments are performed, the data as such are not fully verified and validated through the quality assurance procedures monitoring organizations use to officially submit and certify data on the EPA AQS. Therefore, data are used on the AIRNow web site only for the purpose of reporting the AQI. Information on the AIRNow web site is not used to formulate or support regulation, guidance or any other Agency decision or position.