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About the Facility/Monitor Locator Map - Criteria Air Pollutants

What does the map tell me?

A Facility/Monitor Locator map shows the locations of criteria air pollutant point sources (facilities) and air monitoring sites (monitors). At your discretion, a map may include either facilities or monitors, or both. The map has a symbol at the latitude-longitude coordinates of each facility and monitor. Map shading indicates the states or counties in which facilities or monitors are located.

You can identify a particular facility or monitor in a map by moving your mouse pointer onto the map symbol that represents its location. A "tool tip" window opens and displays information about the facility or monitor. (The descriptive tool tip is available in a map generated in the default, zoom-able image format. It is not available if you change map preferences to a fixed-size image format.)

Information about facilities comes from EPA's National Emission Inventory (NEI) database. Information about monitoring sites comes from EPA's Air Quality System (AQS) database.

To generate a Facility/Monitor Locator map, choose at least one emissions pollutant or monitor pollutant. You may select both pollutant types, and more than one pollutant of each type. Selecting an emissions pollutant includes facilities in the map; selecting a monitor pollutant includes monitors. You also may choose optional criteria to refine data selection and add geographic features to the map.

What does the map look like?

This image shows a Facility/Monitor Locator Map of the state of California. Each shaded county has a monitoring site that measures a selected pollutant, or a facility that releases a selected pollutant. Marker symbols on the map indicate where monitors and facilities are located and what pollutant the monitors measure. The map legend shows the symbol-pollutant associations, how many monitors there are for each pollutant and the total number of facilities. This map also shows optional geographic features: Class I areas (outlined in green) and highways.

How can I customize the map?

Geographic Area
The name of the geographic area previously selected is displayed here. You can click on "change" to choose a different area.

Monitor Pollutant
Selects monitoring sites based on the criteria air pollutants they measure and report to EPA. You may choose any one or more of these pollutants:
  • CO - Carbon monoxide
  • NO2 - Nitrogen dioxide
  • O3 - Ozone
  • SO2 - Sulfur dioxide
  • PM2.5 - Particulate matter (diameter < 2.5 micrometers)
  • PM10 - Particulate matter (diameter < 10 micrometers)
  • Pb - Lead
To omit monitors from a map, select no monitor pollutant. (You will need to select an emissions pollutant.)

Emissions Pollutant
Selects facilities based on the criteria air pollutants and precursors they emit. You may choose any one or more of these pollutants:
  • CO - Carbon monoxide
  • NOx - Nitrogen oxides
  • VOC - Volatile organic compounds
  • SO2 - Sulfur dioxide
  • PM2.5 - Particulate matter (diameter < 2.5 micrometers)
  • PM10 - Particulate matter (diameter < 10 micrometers)
  • NH3 - Ammonia
To omit facilities from a map, select no emission pollutant. (You will need to select a monitor pollutant.)

Emissions Year
The calendar year of air pollutant emissions. If you select an emissions pollutant, you also must select one or more emissions year from the list provided. A facility is included in the map if it emitted a pollutant you select during a year you choose. EPA compiles a national emissions inventory at 3-year intervals (1996, 1999, ...) and updates the National Emission Inventory (NEI) database two to three years after the inventory year. Minor database updates, to amend and correct data, take place at least twice a year. AirData uses the latest database update that has been approved for public release.

Emissions Range   (optional)
Selects facilities based on the amount of pollutant they emit. A facility is included in the map if it had emissions of any selected pollutant within the range you specify, for a year you selected. You may enter a minimum value and/or a maximum value between 0 and 10 million tons. The minimum may not exceed the maximum amount. Entering only a minimum value means "select facilities that emit more than..." Entering only a maximum value means "select facilities that emit no more than..." If you enter neither a minimum nor a maximum value, amount of emissions plays no role in selecting facilities for the map.

Standard Industrial Classification (SIC)   (optional)
Selects facilities based on Standard Industrial Classification -- the type of industry or activity. There are 2-digit SIC codes, which are major classifications, and 4-digit SIC codes, which are detailed classifications. A major classification includes all the detailed classifications whose codes match in the first two digits. You may select up to 10 classifications. Without this option selected, industry type plays no role in determining which facilities to include in a map.

Monitor Type   (optional)
Selects air monitors based on the purpose for which they were established or the monitoring network to which they belong. You may select multiple monitor types. If you do not select this option, monitor type plays no role in determining which monitoring sites to include in a map.

Year Monitor Active   (optional)
Selects monitors that reported data in a particular year. You may select up to eleven years. If you do not select a year, the map includes monitors that reported data in the latest year for which data are available.

Above Air Standard   (optional)
Selects only monitoring sites that reported an air pollutant concentration exceeding the level of a national ambient air quality standard in the year indicated by Year Monitor Active. (You must select a Year Monitor Active in conjunction with this option.) If you do not select this option, monitoring sites are included in the map irrespective of reported pollutant concentrations.

National ambient air quality standards have two forms: concentration and frequency. Concentration-based standards commonly apply to a long-duration value such as yearly average pollutant concentration. The average value may not exceed a specified level. Frequency-based standards usually apply to a short-duration measure such as pollutant concentration for one hour or one day. No more than one value per year may exceed a specified level. The above air standard option selects monitoring sites that failed either type of standard for a single year. This criterion is not the same as determining attainment of an air quality standard, which involves multi-year averaging of concentrations and exceedance counts. A monitoring site selected by the above air standard option is not necessarily failing to attain national air quality standards.

Exceptional Data (optional)
"Exceptional" data are high pollution levels caused by an unusual event such as a wildfire. EPA regulations allow these data, if properly documented and approved by EPA, to be excluded from the determination whether a community met Federal air quality standards. About 6% of monitoring sites report exceptional data in a given year, and EPA approves (excuses) about one-third of the exceptional data, or about 2% of all sites.

You may select this option only in conjunction with the above air standard option. Together, the two options select monitors whose data exceeded the level of an air quality standard, including exceptional data approved (excused) by EPA. If you do not select this option, exceptional data approved by EPA are not used to select monitors whose data exceeded the level of an air quality standard. In either case, monitors are included whose "normal" data and unapproved exceptional data exceeded the level of an air quality standard.

Circle At Monitor Location   (optional)
Adds circles on the map centered at the location of each monitoring site. You set circle size by selecting a radius value, in miles. A circle radius up to 50 miles is valid. The circles can make it easier to see monitor locations on a map, and they provide a sense of scale, since the circle radius is known, and is displayed in the map legend. If you do not enter a radius value, the map does not include circles at monitor locations.

Geographic Features   (optional)
Enhances a map with features such as city locations, highways, and national park outlines. If you do not select this option, the map includes standard features: county or state outlines, and markers at facility and monitor locations.

 

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