I have just got the outdoor sensor working. Initially i was getting quite low readings and they then spiked to 20 -30. for no obvious reason that I could see apart form the fact that we now had heavy rain and 80% humidity. Trawling the net revealed many learned articles revealing the correlation between humidity and pm 2.5 readings such as this one A Big Data Analysis of PM2.5 and PM10 from Low Cost Air Quality Sensors near Traffic Areas - Aerosol and Air Quality Research.
I could not find any algorithm that might help to correct this effect.
Has any one any experience of correcting the sensor values for humidity effects ?