Ultrasonic Humidifiers

Some ultrasonic humidifiers can affect your sensor readings (and ultimately your air quality) by emitting particles measured by the sensor. This will occur if the humidifier’s reservoir is filled with tap water rather than distilled water, as basic tap water contains various minerals and impurities, or if the reservoir and water are dirty. There is not a way to correct this because the sensor is measuring actual particles in the air, including those produced by the humidifier. You can read more from the scientific, peer-reviewed paper, Effect of aerosol particles generated by ultrasonic humidifiers on the lung in mouse.

We’ve gathered a collection of additional articles as well. This resource of external links is found below:

Size and mineral composition of airborne particles generated by an ultrasonic humidifier

Inhalational Lung Injury Associated With Humidifier “White Dust”

Health effects of indoor-air microorganisms

Indoor particle concentrations associated with use of tap water in portable humidifiers

That’s the nightly elevated PM2.5 levels that I was seeing in our bedroom. Apparently they was caused by the small ultrasonic humidifier we use each night.
The higher curve was from a sensor in the bedroom with the humidifier. The lower curve was in another room of our home. So the airborne particulate from the bedroom was circulating through our home.
I think we’ll switch to a non-ultrasonic humidifier, both for health reasons and so our sensors can give more useful PM 2.5 readings.