Thank you for the links. Over the year I have become familiar with Bernd Laquai’s work and have found his papers very useful. The information from the other group of workers is very useful too.
Part of my reason for asking the question originally was to understand if anything was being done by others in the Sensor Community to correct for humidity etc. and determine best practice etc.
Now that I am more familiar with the research and I have investigated the output from some of the more expensive sensors that are used in the UK, I now realise that there is considerable variation in these. This is due to a number of factors including limits of detection.
Therefore, I am starting to think that::
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Unless the humidity is persistent then any errors associated with overcounting due to high humidity are no higher than the difference between higher cost instruments that use different technologies (Eg TEOMs and FIDAS see link below.)
https://www.scottishairquality.scot/sites/default/files/publications/2021-09/Pilot_Research_Study_to_Investigate_PM_Monitorng_Techniques_in_Scotland_issue_1_0.pdf -
As the aim for most countries is to reduce this pollutant based on yearly averages, assuming the weather patterns over a year do not vary year on year, then any reduction seen using the low cost sensors could demonstrate that measures to reduce PM2.5 are effective.
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For realtime sensing, it is better for the counts to be higher than expected than to not count potential hazards. Therefore any overcounting due to high humidity is acceptable and probably falls within the variation of other equipment. Equally, correcting the value using a simple equation such as SDS011 humidity corrected? - #3 by MichaelLazan might be preferred.
These above thoughts are mine only and I am happy for them to be debated, I also need to revisit the FAIREMODE work suggested by Pierre-Jean Guéno to see how they have progressed.