The Air Quality System (AQS) is a repository of ambient air quality data for the EPA. The AQS stores data from over 10,000 monitors run by State, Local, and Tribal Agencies. This data can be downloaded and viewed by the public via the Air Quality System Data Mart.
For more information on the AQS system Visit the EPA's Technology Transfer Network (TTN) Air Quality System (AQS) webpage
Source: US EPA. 2013. For more information on the AQS system Visit the EPA's Technology Transfer Network (TTN) Air Quality System (AQS). Accessed on 10 September 2013. Available online at: http://www.epa.gov