We are implementing some changes to the way we report PM10 particulate levels on our website, in line with new guidance recently issued by Defra.
The new guidance updates Defra’s Air Pollution Index to reference equivalent PM10, replacing the old index that was only applicable to PM10 measurements recorded by a particular type of analyser (the TEOM). This allows us to report pollution indices and bandings for PM10 measurements made by equipment other than TEOMs.
At the same time we are implementing the conversion of TEOM PM10 data to reference equivalent PM10 using the Volatile Correction Model (VCM) method. Reference equivalent PM10 is considered a more accurate measure of ambient PM10 levels. Initially we are implementing this change on our hourly and daily bulletin, and on our graphs and data downloads.
Whilst we are taking care to make sure that everything works, please be aware that there is increased risk that some of the web pages may not work correctly during this period. Please feel free to tell us if you notice anything that isn't working, or if you are unsure of any of the figures.
For more information about the Volatile Correction Model please follow the link below.

More Information

Item date 14/08/2009