However, unlike the other territories in Australia, WA DER is not providing the readings in raw ppm and µg/m3, but directly in AQI. The AQI scale used by the WA DER is not the same as the one from the US EPA, which we are using for all the stations reported on the World Air Quality Index project. So this aim of the FAQ entry is to explain how the convertion between the two AQI scales is done.
|Pollutant||Averaging period||Maximum concentration||Raw data convertion formula|
|Fine Particles (PM2.5)||1 day||25µg/m3||Mass = AQI*25/100 (µg/m3)|
|Respirable Particles (PM10)||1 day||50µg/m3||Mass = AQI*50/100 (µg/m3)|
|Carbon monoxide (CO)||8 hours||9.0ppm||Count = AQI*9.0/100 (ppm)|
|Nitrogen dioxide (NO2)||1 hour||0.12ppm||Count = AQI*0.12/100 (ppm)|
|Sulfur dioxide (SO2)||1 hour||0.20ppm||Count = AQI*0.20/100 (ppm)|
|1 hour||0.10ppm||Count = AQI*0.10/100 (ppm)|
Actually, surprisingly enough, the WA DER AQI scale is much more strict than the US EPA when the AQI is above 50! Check for this comparitive tables for PM2.5:
And this comparison is for the PM10:
For now, we will keep the using the US EPA standard, simply because it is the one we use for the overall Australia.
We will also post an update soon (by October 2014), once we have gathered more data, to do more comparison of those 2 scales. We currently assume that the Air Quality in Western Australia is not just the same as in Chinam, where AQI above 200 is common, and that AQI below 50 should be the norm, in which case the PM2.5 reported AQI should be similar for both scales (assuming that PM2.5 is the major pollutant). But for now, those are all assumptions, so let's see in one month one enough data is available.