Is there a way to avoid moisture accumulation? periodic heating through an element?
On behalf of James Frame:
There are several potential solutions. In general you need to either raise the temperature of the surfaces of concern above the dew point, or lower the humidity near the sensor so again it is below the dew point. You could also look into treating the surface of concern with a hydrophobic coating, which would reduce but eliminate the challenge. Heaters are commonly used in condensing environments. Water traps are used in things like capnography sensors, but this would likely also strip out most particulates.
If you are operating near or beyond the dew point, you may have enough water droplets in the air to distort a particle measurement. Particles also serve as nucleation sites for water droplets, which increases the measured size of the particle (but does not change the effect the particle has in the lungs if you are looking at pollution monitoring).