It does not measure water vapor, at least not the one I'm using (PMS5003). I always have windows tightly shut because of the extreme pollution outside, so 100%

It does not measure water vapor, at least not the one I'm using (PMS5003). I always have windows tightly shut because of the extreme pollution outside, so 100% humidity is easy to reach simply by mopping the floors (which stay wet for hours after). It does not change PM measurements one bit. Fry a couple of eggs though, and PM 2.5 quickly goes over 100 µg/m³. Burn a piece of meat just a little bit and see it rise over 300 µg/m³.