This site reflects the current Air Quality Index (AQI). The cut points for ozone were revised on March 12, 2008 along with the national ambient air quality standard for ozone. If you are a regular visitor to this site, you may notice a lower level of unhealthy days in the archived maps due to the revised ozone cut points being used for maps after April 24, 2008.

About the Data | For research and decision-making exercises | For feeds of AIRNOW data

Map File Name Directory (Excel Spreadsheet, 199 KB)

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(Air Quality System). 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.

For research and decision-making exercises

To access data that are more suitable for research applications or other more formal decision-making exercises, please use the AQS Data Mart. The intended users of the AQS Data Mart are air quality data analysts in the regulatory, academic, and health research communities.  The Data Mart is intended for those who need to download large volumes of detailed technical data stored at EPA. The Data Mart does not provide any interactive analytical tools.

AQS Data Mart @ http://www.epa.gov/ttn/airs/aqsdatamart/

If you are interested in summary data or graphical displays, there are other applications available:

AirData @ http://www.epa.gov/air/data/index.html
AirExplorer @ http://www.epa.gov/airexplorer/

For feeds of AIRNOW data

To access feeds of AIRNow data in the form of web services or ftp access, please visit http://www.airnowgateway.org and request an account.