Ambient Air Monitoring and Emissions Measurement

Definition
Overview
How do I monitor for air pollutants in the ambient air or from emission sources?

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

Emissions Measurement is the process of monitoring particulate and gaseous emissions from a specific source.

Top of page

Air quality monitoring is carried out to assess the extent of pollution, ensure compliance with national legislation, evaluate control options, and provide data for air quality modeling. There are a number of different methods to measure any given pollutant, varying in complexity, reliability, and detail of data. These range from simple passive sampling techniques to highly sophisticated remote sensing devices. A monitoring strategy should carefully examine the options to determine which methodology is most appropriate, taking into account initial investment costs, operating costs, reliability of systems, and ease of operation.

The locations for monitoring stations depend on the purpose of the monitoring. Most monitoring networks are designed with human health objectives in mind, and monitoring stations are therefore established in population centers. Many governments (local, regional or national) give specific guidelines on where to monitor within these areas - next to busy roads, in city center locations, or at a location of particular concern (e.g., a school, hospital). Background monitoring stations are also established, to act as a "control" when determining source apportionment.

Emissions Measurement is the science of characterizing and measuring air pollutant emissions. The measurement of both type and quantity of these contaminants is an important part of obtaining the data needed to implement a meaningful control program. The process of monitoring particulate and gaseous emissions from a stationary source is often referred to as source sampling or source testing.

Once data are collected from a monitoring system, they must be stored in data management systems and databases. Subsequently, the data must be retrieved and analyzed to see what they reveal about the effectiveness of regulatory standards, the accuracy of modeling, impacts on health endpoints, and as an overall way of assessing. In the U.S. these data are collected and housed in the Air Quality Subsystem (AQS). The AQS contains ambient air pollution data collected by EPA, state, local, and tribal air pollution control agencies from thousands of monitoring stations.  AQS also contains meteorological data, descriptive information about each monitoring station (including its geographic location and its operator), and data quality assurance/quality control information. 

Top of page

Chapters 6 and 7 of U.S. EPA's Introduction to Air Pollution Control online course provide specific methods and principles for ambient air quality monitoring and the measurement of pollutant emissions. This course is designed to present an introductory view of all major, practical aspects of air pollution control, intended primarily for those unfamiliar with governmental control of air pollution or those who require a general knowledge of the principles and practices associated with air pollution control.

To learn about the U.S. EPA's Air Quality System (AQS) you may visit the AQS website or access the computer based training by clicking here (this link will prompt you to download a 35 MB file).

As with the other management activities related to the AQM process, it is critical to contact the regulated community and other affected parties, as the public should be consulted as part of the process.

Resources

Publications and Reports

Tools and Training

Top of page