[Steve1506]

Add between 10 and 20 to the offset and you should be about right, notice you are in Crewkerne so small town background levels will be 410pp upwards. (I visit Barrington regularly.)

Thanks for the advice Interesting that you visit this way I live on the hill behind the hospital overlooking the town so very clear ai I have had the AQM running now for over 24hrs outside and it is looking good AQ  is showing around 25 and the CO2 varies around the 390 mark so will offset by 20 to bring it in line. Hope to get the rest of my new station online in the coming weeks I have had the parts around for a while just no spare time to figure it all out.

Steve D