AirData

What does the chart tell me?

An Emissions by Category Chart shows the relative annual emissions of criteria air pollutants in 13 major categories of emissions sources, which EPA calls tier-1 categories. Tier-1 categories include industry sectors such as electric power utilities, and activities such as driving vehicles. The tier-1 categories encompass all types of sources -- stationary and mobile, large and small. The chart omits emissions from the 14-th tier-1 category, natural sources, however.

In an Emissions by Category Chart, each tier-1 category is represented by a bar whose length is proportional to the category's total emissions in the geographic area and year you selected. Tier-1 categories are displayed in descending order of their emissions; the longest bar is at the top of the chart and the shortest bar at the bottom. The emissions amount for each category is listed beside the corresponding bar.

If you select a single pollutant for an Emissions by Category Chart, bar lengths indicate each category's emissions of that pollutant. If you select multiple pollutants, the bars are segmented. The length of each segment represents the emissions of a pollutant, and the total bar length represents the sum of the emissions of the selected pollutants for the category. All bar segments associated with a particular pollutant have the same shading pattern and color, which is identified in a chart legend. Positioning the mouse pointer on a bar segment displays a tool tip containing pollutant name and emissions.

To generate an Emissions by Category Chart, select one or more pollutants, and a year.

Emissions data for this chart come from EPA's National Emissions Inventory database. See About the NEI Database for information about the data.

Displaying the sum of PM10 and PM2.5 emissions in a chart may be misleading. PM10 emissions include all particle sizes smaller than 10 micrometers, which includes PM2.5 emissions of particles smaller than 2.5 micrometers.

Due to changes in EPA emission inventory procedures, 1999 emissions may not be directly comparable with prior years, especially with regard to particulate matter emissions.

What does the chart look like?

This image is a typical chart, showing a state's emissions of two pollutants in each of the tier-1 categories of sources. Bar segments indicate the relative magnitude of carbon monoxide and nitrogen oxides emissions in each category. Bar lengths indicate each category's total CO + NOx emissions, and the numeric value is displayed beside each bar.

How can I customize the chart?

Geographic Area

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

Pollutant Emitted

Emissions of the pollutant(s) you select are displayed in the chart. Choose one or more of the criteria air pollutants or precursors:

• CO - Carbon monoxide
• NOx - Nitrogen oxides
• VOC - Volatile organic compounds
• SO2 - Sulfur dioxide
• PM2.5 - Particulate matter (size < 2.5 micrometers)
• PM10 - Particulate matter (size < 10 micrometers)
• NH3 - Ammonia

Year

The calendar year of pollutant emissions displayed in the chart. Choose one of the available years.