{"id":1230,"date":"2014-01-16T14:26:25","date_gmt":"2014-01-16T19:26:25","guid":{"rendered":"http:\/\/atipure.com\/store\/?post_type=avada_faq&p=1230"},"modified":"2026-04-04T12:43:51","modified_gmt":"2026-04-04T17:43:51","slug":"how-is-the-aqi-calculated","status":"publish","type":"avada_faq","link":"https:\/\/atipure.com\/store\/?avada_faq=how-is-the-aqi-calculated","title":{"rendered":"How is the AQI calculated?"},"content":{"rendered":"

The AQI is a calculated index that provides Ontarians with air quality information in near real-time.\u00a0 This index has its own concentration breakpoints for the descriptive categories (i.e. very good, good, moderate, poor, and very poor).\u00a0 It may be difficult to compare AQI calculations from jurisdiction to jurisdiction across North America because they are not standardized and the formulas involved are complex.<\/p>\n

The relationship between AQI and the individual pollutant concentrations are shown below.\u00a0 For each category, a linear relationship is assumed between index values and the concentrations of the sub-index pollutant.\u00a0 At the end of each hour, the concentration of each pollutant measured at individual AQI sites is converted into a number ranging from zero upwards using a common scale or index. The calculated number for each pollutant is referred to as a sub-index. At a given site, the highest sub-index becomes the AQI reading for that hour at that location.<\/p>\n\n\n\n\n\n\n\n\n\n
\n

Ozone (O3<\/sub>)<\/b><\/p>\n<\/td>\n<\/tr>\n

\n

AQI Category<\/b><\/p>\n<\/td>\n

\n

[O3<\/sub>] (ppb)<\/b><\/p>\n<\/td>\n
\n

AQI Equation<\/b><\/p>\n<\/td>\n<\/tr>\n

Very Good<\/td>\n0 to 23<\/td>\n0.6520 \u00d7 [O3<\/sub>] + 0<\/td>\n<\/tr>\n
Good<\/td>\n24 to 50<\/td>\n0.5800 \u00d7 [O3<\/sub>] + 2.154<\/td>\n<\/tr>\n
Moderate<\/td>\n51 to 80<\/td>\n0.5900 \u00d7 [O3<\/sub>] + 2.1<\/td>\n<\/tr>\n
Poor<\/td>\n81 to 149<\/td>\n0.7200 \u00d7 [O3<\/sub>] – 8.37<\/td>\n<\/tr>\n
Very Poor<\/td>\n>149<\/td>\n0.7200 \u00d7 [O3<\/sub>] – 8.37<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n\n\n\n\n\n\n\n\n\n
\n

Fine Particulate Matter (PM2.5<\/sub>)<\/b><\/p>\n<\/td>\n<\/tr>\n

\n

AQI Category<\/b><\/p>\n<\/td>\n

\n

[PM2.5<\/sub>] 3-hour
\naverage (\u00b5g\/m3<\/sup>)<\/b><\/p>\n<\/td>\n

\n

AQI Equation<\/b><\/p>\n<\/td>\n<\/tr>\n

Very Good<\/td>\n<12<\/td>\n1.364 \u00d7 [PM2.5<\/sub>] + 0<\/td>\n<\/tr>\n
Good<\/td>\n12 to 22<\/td>\n1.500 \u00d7 [PM2.5<\/sub>] – 2.000<\/td>\n<\/tr>\n
Moderate<\/td>\n23 to 45<\/td>\n0.7727 \u00d7 [PM2.5<\/sub>] + 14.228<\/td>\n<\/tr>\n
Poor<\/td>\n46 to 90<\/td>\n1.113 \u00d7 [PM2.5<\/sub>] – 1.298<\/td>\n<\/tr>\n
Very Poor<\/td>\n>90<\/td>\n1.100 \u00d7 [PM2.5<\/sub>] + 0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n\n\n\n\n\n\n\n\n\n
\n

Sulphur Dioxide (SO2<\/sub>)<\/b><\/p>\n<\/td>\n<\/tr>\n

\n

AQI Category<\/b><\/p>\n<\/td>\n

\n

[SO2<\/sub>] (ppb)<\/b><\/p>\n<\/td>\n

\n

AQI Equation<\/b><\/p>\n<\/td>\n<\/tr>\n

Very Good<\/td>\n0 to 79<\/td>\n0.1899 \u00d7 [SO2<\/sub>] + 0<\/td>\n<\/tr>\n
Good<\/td>\n80 to 169<\/td>\n0.1685 \u00d7 [SO2<\/sub>] + 2.520<\/td>\n<\/tr>\n
Moderate<\/td>\n170 to 250<\/td>\n0.2125 \u00d7 [SO2<\/sub>] \u2013 4.125<\/td>\n<\/tr>\n
Poor<\/td>\n251 to 1999<\/td>\n0.0280 \u00d7 [SO2<\/sub>] + 42.97<\/td>\n<\/tr>\n
Very Poor<\/td>\n>1999<\/td>\n0.0500 \u00d7 [SO2<\/sub>] + 0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n\n\n\n\n\n\n\n\n\n
\n

Nitrogen Dioxide (NO2<\/sub>)<\/b><\/p>\n<\/td>\n<\/tr>\n

\n

AQI Category<\/b><\/p>\n<\/td>\n

\n

[NO2<\/sub>] (ppb)<\/b><\/p>\n<\/td>\n

\n

AQI Equation<\/b><\/p>\n<\/td>\n<\/tr>\n

Very Good<\/td>\n0 to 50<\/td>\n0.300 \u00d7 [NO2<\/sub>] + 0<\/td>\n<\/tr>\n
Good<\/td>\n51 to 110<\/td>\n0.2543 \u00d7 [NO2<\/sub>] + 3.00<\/td>\n<\/tr>\n
Moderate<\/td>\n111 to 200<\/td>\n0.191 \u00d7 [NO2<\/sub>] + 10.79<\/td>\n<\/tr>\n
Poor<\/td>\n201 to 524<\/td>\n0.1517 \u00d7 [NO2<\/sub>] + 19.5<\/td>\n<\/tr>\n
Very Poor<\/td>\n>524<\/td>\n0.1903 \u00d7 [NO2<\/sub>] + 0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n\n\n\n\n\n\n\n\n\n
\n

Carbon Monoxide (CO)<\/b><\/p>\n<\/td>\n<\/tr>\n

\n

AQI Category<\/b><\/p>\n<\/td>\n

\n

[CO] (ppm)<\/b><\/p>\n<\/td>\n

\n

AQI Equation<\/b><\/p>\n<\/td>\n<\/tr>\n

Very Good<\/td>\n0 to 12.49<\/td>\n1.2500 \u00d7 [CO] + 0<\/td>\n<\/tr>\n
Good<\/td>\n12.50 to 22.49<\/td>\n1.6700 \u00d7 [CO] – 5.67<\/td>\n<\/tr>\n
Moderate<\/td>\n22.50 to 30.49<\/td>\n2.4300 \u00d7 [CO] – 23.86<\/td>\n<\/tr>\n
Poor<\/td>\n30.50 to 49.49<\/td>\n2.7200 \u00d7 [CO] – 34.39<\/td>\n<\/tr>\n
Very Poor<\/td>\n>49.49<\/td>\n2.0000 \u00d7 [CO] + 0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n\n\n\n\n\n\n\n\n\n
\n

Total Reduced Sulphur (TRS)<\/b><\/p>\n<\/td>\n<\/tr>\n

\n

AQI Category<\/b><\/p>\n<\/td>\n

\n

[TRS] (ppb)<\/b><\/p>\n<\/td>\n

\n

AQI Equation<\/b><\/p>\n<\/td>\n<\/tr>\n

Very Good<\/td>\n0 to 5.49<\/td>\n3.0000 \u00d7 [TRS] + 0<\/td>\n<\/tr>\n
Good<\/td>\n5.50 to 10.49<\/td>\n3.7500 \u00d7 [TRS] – 6.50<\/td>\n<\/tr>\n
Moderate<\/td>\n10.50 to 27.49<\/td>\n1.0625 \u00d7 [TRS] + 20.31<\/td>\n<\/tr>\n
Poor<\/td>\n27.50 to 999.49<\/td>\n0.05046 \u00d7 [TRS] + 48.59<\/td>\n<\/tr>\n
Very Poor<\/td>\n>999.49<\/td>\n0.1000 \u00d7 [TRS] + 0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Notes:<\/i><\/b><\/p>\n

    \n
  • parts per billion (ppb)<\/i><\/li>\n
  • micrograms per cubic metre (\u00b5g\/m3<\/sup>)<\/i><\/li>\n
  • parts per million (ppm)<\/i><\/li>\n<\/ul>\n
    <\/div><\/div><\/div><\/div><\/div><\/p>\n","protected":false},"excerpt":{"rendered":"

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