Air quality index, loftvís

To estimate air quality, or figure out the current conditions, one needs to know the different units of measure, µg/m3, or mg/m3, and the different health limits for the different pollutants. Also, short term pollution limits are not the same as 24-hour health limits.
Examples of available data are measurements of PM10:
NO2:
and H2S:
It is possible to show these in a simpler way, using an index that accounts for the health limits. Thus, a value of 1 for the index, I, means that one of the pollutants has reached it’s limit. Higher values than 1 mean that they have been exceeded, and lower values than 1 mean that the air quality is better. Below is an example for the past week:

It is clear that the air quality has been rather good lately. If we look at the whole year, we see that on 10-11 January the 24-hour health limit was exceeded (here using a running 24-hour mean), and that it was due to PM10.














We can also show more current conditions this way. Several pollutants do though not have public health limits for shorter periods than 24-hours. Also, using hourly values would lead to very rapidly fluctuating values, since short peaks (real and in the data) complicate things. Therefore I show 4-hour averages, which give good indication about the current conditions (using 50 µg/m3 for PM10 and H2S, but 110 µg/m3 for NO2, is 75 for 24-hours).