Uniform Air Quality Index (AQI) and Daily Reporting

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1 Areas are generally required to report the AQI based on 8-hour ozone values. However, there are a small number of areas where an AQI based on 1-hour ozone values would be more precautionary. In these cases, in addition to calculating the 8-hour ozone index value, the 1-hour ozone index value may be calculated, and the maximum of the two values reported. 2 8-hour O3 concentrations do not define higher AQI values (>301). AQI values > 301 are calculated with 1-hour O3 concentrations. 3 1-hr SO2 concentrations do not define higher AQI values (≥200). AQI values of 200 or greater are calculated with 24-hour SO2 concentration. 4 AQI values between breakpoints are calculated using equation 1 to this appendix. For AQI values in the hazardous category, AQI values greater than 500 should be calculated using equation 1 and the concentration specified for the AQI value of 500. The AQI value of 500 are as follows: O3 1-hour—0.604 ppm; PM2.5 24-hour—325.4 µg/m3; PM10 24-hour—604 µg/m3; CO ppm—50.4 ppm; SO2 1-hour—1004 ppb; and NO2 1-hour—2049 ppb.

Referencing norms: co-500, no2-500, pm10-500, pm25-500, so2-500

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Table 2 to Section 3.4 of Appendix G—Breakpoints for the AQI These breakpoints Equal these AQI's O3 (ppm) 8-hour O3 (ppm) 1-hour1 PM2.5 (µg/m3) 24-hour PM10 (µg/m3) 24-hour CO (ppm) 8-hour SO2 (ppb) 1-hour NO2 (ppb) 1-hour AQI Category 0.000-0.054 0.0-9.0 0-54 0.0-4.4 0-35 0-53 0-50 Good. 0.055-0.070 9.1-35.4 55-154 4.5-9.4 36-75 54-100 51-100 Moderate. 0.071-0.085 0.125-0.164 35.5-55.4 155-254 9.5-12.4 76-185 101-360 101-150 Unhealthy for Sensitive Groups. 0.086-0.105 0.165-0.204 55.5-125.4 255-354 12.5-15.4 3 186-304 361-649 151-200 Unhealthy. 0.106-0.200 0.205-0.404 125.5—225.4 355-424 15.5-30.4 3 305-604 650-1249 201-300 Very Unhealthy. 0.201−(2) 0.405+ 225.5+ 425+ 30.5+ 3 605+ 1250+ 301+ 4 Hazardous.

Referencing norms: cat-good, cat-hazardous, cat-moderate, cat-ufsg, cat-unhealthy, cat-very, co-1, co-2, co-3, co-4, co-5, co-ceiling, no2-1, no2-2, no2-3, no2-4, no2-5, no2-ceiling, o3-8h-1, o3-8h-2, o3-8h-3, o3-8h-4, o3-8h-5, o3-8h-ceiling, pm10-1, pm10-2, pm10-3, pm10-4, pm10-5, pm10-ceiling, pm25-1, pm25-2, pm25-3, pm25-4, pm25-5, pm25-ceiling, so2-1, so2-2, so2-3, so2-ceiling