Title 40


Appendix G to Part 58 - Uniform Air Quality Index (AQI) and Daily Reporting

40: : Appendix G

Appendix G to Part 58 - Uniform Air Quality Index (AQI) and Daily Reporting General Requirements

1. What is the AQI?

2. Why report the AQI?

3. Must I report the AQI?

4. What goes into my AQI report?

5. Is my AQI report for my MSA only?

6. How do I get my AQI report to the public?

7. How often must I report the AQI?

8. May I make exceptions to these reporting requirements?


9. How Does the AQI Relate to Air Pollution Levels?

10. What Monitors Should I Use To Get the Pollutant Concentrations for Calculating the AQI?

11. Do I have to forecast the AQI?

12. How Do I Calculate the AQI?

Background and Reference Materials

13. What Additional Information Should I Know?

General Requirements 1. What Is the AQI?

The AQI is a tool that simplifies reporting air quality to the general public. The AQI incorporates into a single index concentrations of 5 criteria pollutants: ozone (O3), particulate matter (PM), carbon monoxide (CO), sulfur dioxide (SO2), and nitrogen dioxide (NO2). The scale of the index is divided into general categories that are associated with health messages.

2. Why Report the AQI?

The AQI offers various advantages:

a. It is simple to create and understand.

b. It conveys the health implications of air quality.

c. It promotes uniform use throughout the country.

3. Must I Report the AQI?

You must report the AQI daily if yours is a metropolitan statistical area (MSA) with a population over 350,000.

4. What Goes Into My AQI Report?

i. Your AQI report must contain the following:

a. The reporting area(s) (the MSA or subdivision of the MSA).

b. The reporting period (the day for which the AQI is reported).

c. The critical pollutant (the pollutant with the highest index value).

d. The AQI (the highest index value).

e. The category descriptor and index value associated with the AQI and, if you choose to report in a color format, the associated color. Use only the following descriptors and colors for the six AQI categories:

Table 1 - AQI Categories

For this AQI Use this descriptor And this color 1
0 to 50 “Good” Green.
51 to 100 “Moderate” Yellow.
101 to 150 “Unhealthy for Sensitive Groups” Orange.
151 to 200 “Unhealthy” Red.
201 to 300 “Very Unhealthy” Purple.
301 and above “Hazardous” Maroon. 1