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.
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