Ultrasonic Humidifiers

Sensors
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Some ultrasonic humidifiers can generate PM (and ultimately affect 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 isn’t a way to correct this as the sensor is measuring actual particles in the air, including those produced by the humidifier. You can read more about this topic in this scientific, peer-reviewed paper:

Particulate matter emitted from ultrasonic humidifiers-Chemical composition and implication to indoor air.

Additional Resources

We’ve gathered a collection of other articles and studies that discuss ultrasonic humidifiers as well.

Studies

Articles

Learn More

Air Quality Index (AQI)
Why Should I Put My Indoor Sensor On The Map?
What Do PurpleAir Sensors Measure and How Do They Work?

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Humidifier effect
Humidifier effect497×523 113 KB

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.

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