• How the air quality bands are calculated (1st January 2012 onwards)
Band Index Ozone Nitrogen
Dioxide
Sulphur
Dioxide
PM2.5
Particles
PM10
Particles
Running 8
hourly mean
Hourly
mean
15 minute
mean
24 hour
mean
24 hour
mean
µg m-3 µg m-3 µg m-3 µg m-3 µg m-3
Low  
  1 0-33 0-67 0-88 0-11 0-16
2 34-66 68-134 89-177 12-23 17-33
3 67-100 135-200 178-266 24-35 34-50
Moderate  
  4 101-120 201-267 267-354 36-41 51-58
5 121-140 268-334 355-443 42-47 59-66
6 141-160 335-400 444-532 48-53 67-75
High  
  7 161-187 401-467 533-710 54-58 76-83
8 188-213 468-534 711-887 59-64 84-91
9 214-240 535-600 888-1064 65-70 92-100
Very High  
  10 241 or more 601 or more 1065 or more 71 or more 101 or more
Pollution concentrations recorded by the LAQN analysers have been classified according to Defra's Air Pollution Index system. This classes levels into bands from 'low' to 'very high'. Each band is subdivided into three to produce an Air Pollution Index, from 1 to 10, 1 being 'low', 10 being 'very high'. Measurements are rounded to the nearest whole number. The concentrations are classified according to the table above. Note that different pollutants have different concentrations and averaging periods, related to the estimated health effects of each.
Read a technical explanation of how the new index bands (1st January 2012 onwards) are calculated here
See the bands for before the 1st January 2012     Go back to the bulletin page