After a couple of years, I am getting much lower readings than I would expect. How do I know that it is the sensor failing or the environment changing?
Sensors don’t usually slowly decline - they fail suddenly. If the A and B sensor data agree well, then it’s working. Failures are often debris that can be blown out with canned air. Sometimes a fan will fail. PAs can last 5 year or more - not always but there’s nothing that has a lifetime of a year or 2.
Thanks. It is a gonner, I think. I have been measuring PM2.5 from a restaurant below me and the restaurant is still there, but the readings are way, way down. You can see the paper I wrote on this site. Under Research. Domestic indoor air quality arising from commercial cooking sources
I will take if off air.