IITM

IITM

IMD ESSO GAW

SAFAR - India

System of Air Quality and Weather Forecasting And Research
Ministry of Earth Science, Govt. of India.
Indian Institute of Tropical Meteorology, Pune


Air Quality Index

 


 

1.Air Quality Index is a tool for effective communication of air quality status to people in terms, which are easy to understand. It transforms complex air quality data of various pollutants into a single number (index value), nomenclature and colour.

 

2.  There are six AQI categories, namely Good + Satisfactory, Moderately polluted, Poor, Very  Poor,  and  Severe.  Each  of  these  categories  is  decided  based  on  ambient concentration values of air pollutants and their likely health impacts (known as health breakpoints). AQ sub-index and health breakpoints are evolved for eight pollutants (PM10, PM2.5, NO2, SO2, CO, O3, NH3, and Pb) for which short-term (upto 24-hours)
National Ambient Air Quality Standards are prescribed.

 

3.Based on the measured ambient concentrations of a pollutant, sub-index is calculated,
which is a linear function of concentration (e.g. the sub-index for PM2.5 will be 51 at concentration 31 µg/m3, 100 at concentration 60 µg/m3, and 75 at concentration of 45
µg/m3). The worst sub-index determines the overall AQI. AQI categories and health breakpoints for the eight pollutants are as follow: 

 

 

 

 

 

Description

 

AQI

PM10

µg/m3

24 hr avg

PM2.5

µg/m3

24 hr avg

CO

ppm

8 hr avg

O3

ppb

8 hr avg

NO2

ppb

24 hr avg

Good + Satisfactory

0-100

0-100

0-60

0-1.7

0-50

0-43

Moderate

101-200

101-250

61-90

1.8-8.7

51-84

44-96

Poor

201-300

251-350

91-120

8.8-14.8

85-104

97-149

Very Poor

301-400

351-430

121-250

14.9-29.7

105-374

150-213

Severe

401-500

431-550

251-350

29.8-40

375-450

214-750

 

 

 

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