Air quality monitors used by governments will condition the air to ensure the relative humidity is set correctly. They therefore are not affected by humidity.
However, home air quality monitors like the Laser Egg or AirVisual Pro are affected by humidity. Often, a simple formula can be used to account for changes in humidity.
For more information, see here: https://www.quora.com/How-does-humidity-affect-air-quality-ratings-for-PM-2-5-and-PM-10
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