Ambient Air Monitoring

Ambient air monitoring is the systematic, long-term assessment of pollutant levels by measuring the quantity and types of certain pollutants in the surrounding, outdoor air.

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Ambient air monitoring is an integral part of an effective air quality management system. Reasons to collect such data include to:

  • assess the extent of pollution;
  • provide air pollution data to the general public in a timely manner;
  • support implementation of air quality goals or standards;
  • evaluate the effectiveness of emissions control strategies;
  • provide information on air quality trends;
  • provide data for the evaluation of air quality models; and
  • support research (e.g., long-term studies of the health effects of air pollution).

There are different methods to measure any given pollutant. A developer of a monitoring strategy should examine the options to determine which methods are most appropriate, taking into account the main uses of the data, initial investment costs for equipment, operating costs, reliability of systems, and ease of operation.

The locations for monitoring stations depend on the purpose of the monitoring. Most air quality monitoring networks are designed to support human health objectives, and monitoring stations are established in population centers. They may be near busy roads, in city centers, or at locations of particular concern (e.g., a school, hospital, particular emissions sources). Monitoring stations also may be established to determine background pollution levels, away from urban areas and emissions sources.

Systems are needed to ensure that data are of acceptable quality, to record and store the data, and to analyze the data and present results.

Information on ambient air monitoring in the United States

Most of the ambient air monitoring networks supporting air quality management are designed and operated by tribal, state, or local governments. EPA develops requirements and guidance for the design and operation of these networks. The requirements are in the Code of Federal Regulations Exitunder Title 40. Requirements related to methods are in the appendices to Part 50 and in Part 53. Network requirements are in Part 58 – Ambient Air Quality Surveillance.

EPA's Ambient Monitoring Technology Information Center (AMTIC) contains technical information on monitoring programs, including the networks of state or local air monitoring stations (SLAMS), monitoring methods, and quality assurance and control procedures.

The Air Quality System is a national repository of ambient air pollution data collected by EPA, state, local, and tribal air pollution control agencies. It also contains meteorological data, descriptive information about each monitoring station (including its geographic location and its operator), and data quality assurance/quality control information. 

EPA's AirData provides public access to monitored air quality data, including the ability to download data, create summary reports, visualize the data, and access an interactive map of monitors.  AirNow provides easy access to real-time and forecast air quality information using the Air Quality Index, which helps you understand what local air quality means to your health.

Tools for the international community

AirNow-International is a stand-alone international version of  U.S. EPA's AirNow system. By participating in a community of AirNow-International users, a country can share information and learn from colleagues around the world.