Several government agencies have joined efforts to develop AIRNow.gov, a website providing public access to the quality of air nationwide. They include the U.S. EPA and National Oceanic and Atmospheric Association, among others.
The web portal shows data on five major air pollutants the EPA monitors in accordance with the Clean Air Act: ground-level ozone, particle pollution (particulate matter), carbon monoxide, sulfur dioxide and nitrogen dioxide. AIRNow offers daily forecasts on air quality nationwide, as well as real-time air quality information for 300 U.S. cities.
State, local agencies and tribal organizations contribute data to the website. The monitoring techniques they use are in accordance with those used by federal agencies and all data collected are displayed as soon as practical at the end of every hour.