Concentration scales
The concentration scales for NO2, SO2 and PM10 are based on the new European guidelines
concerning the assessment and management of ambient air quality.
Based on the number of allowed exceedances of the new European limit values, an index
value of 6, 7 or 8 is assigned to that limit value. The other scale divisions were defined
by evaluating the range of concentrations measured in the telemetric networks of the three
Belgian Regions.
The concentration scales for O3 are based on the threshold of 180 µg/m³ (European threshold for informing the public) and 360 µg/m³ (alarm threshold) as 1 hour averages.
For CO, the highest percentiles measured in the past correspond to color index 8, 9. Color index 1 corresponds with percentile 30 . There are not enough historic measurements to define a color index for PM2.5.
The table below shows the correlation between the measured concentrations (µg/m³), the concentration scale (between 1 and 10) and the rating for O3, NO2, CO, SO2 en PM10.
Pollutant | average | unit | scale |
|||||||||
O3 |
1 hour |
µg/m3 | 0 - 30 |
31 - 50 |
51 - 70 |
71 - 90 |
91 - 110 |
111 - 145 |
146 - 180 |
181 - 250 |
251 - 360 |
> 360 |
NO2 |
1 hour |
µg/m3 | 0 - 25 |
26 - 45 |
46 - 60 |
61 - 80 |
81 - 110 |
111 - 150 |
151 - 200 |
201 - 270 |
271 - 400 |
> 400 |
CO |
1/2 hour |
mg/m3 | 0 - 1,4 |
1,5 - 2,1 |
2,2 - 2,8 |
2,9 - 3,6 |
3,7 - 4,5 |
4,6 - 5,2 |
5,3 - 6,6 |
6,7 - 8,4 |
8,5 - 13,7 |
> 13,7 |
SO2 |
running 24-hour | µg/m3 | 0 - 15 |
16 - 30 |
31 - 45 |
46 - 60 |
61 - 80 |
81 - 100 |
101 - 125 |
126 - 165 |
166 - 250 |
> 250 |
PM10 |
running 24-hour | µg/m3 | 0 - 10 |
11 - 20 |
21 - 30 |
31 - 40 |
41 - 50 |
51 - 70 |
71 - 100 |
101 - 150 |
151 - 200 |
> 200 |
C6H6 | running 24-hour | µg/m3 | 0 - 0,50 |
0,51 - 1,00 |
1,01 - 1,25 |
1,26 - 1,50 |
1,51 - 2,75 |
2,76 - 3,50 |
3,51 - 5,00 |
5,01 - 7,50 |
7,51 - 10,00 |
> 10,00 |
color | 1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
||
rating |
exellent |
very good |
good |
fairly good |
moderate |
poor |
very poor |
bad |
very bad |
horrible |