Do Home Humidifiers Affect My Air Quality?

by Kieran Berryman

Ultrasonic humidifier | Purpleair

Humidifiers are a staple item in many households due to their various benefits. If you think about it, it’s really no surprise that a machine with the ability to moisturize dry skin, ease dry congestion, and reduce allergy symptoms is a popular pick. But, given that they shoot small water droplets up into the air, have you ever wondered if they affect air quality?


It may have never crossed your mind, and even if it did, you couldn’t be blamed for assuming that they could only help. But that’s not necessarily the case. On the contrary, some models of humidifiers have actually been proven to raise air pollution levels. It all depends on the mechanism your humidifier uses to disperse water droplets.

Methods of Water Dispersion

There are many different types of humidifiers that you might have seen or used in your daily life. Your home, for example, may contain some sort of central humidifier, which is built into your HVAC system. However, that is not the type of humidifier I’m talking about here. Portable humidifiers are most often the culprit, but they’re not all built the same. There are four main types of portable humidifiers that I’m going to talk about here: evaporative, vaporizer, impeller, and ultrasonic.


According to the U.S. EPA:

  • Evaporative humidifiers transmit water droplets by blowing air through a moistened material.

  • Vaporizer humidifiers create steam by heating water using some sort of electrical element.

  • Impeller humidifiers produce mist by way of a high-speed rotating disk.

  • Ultrasonic humidifiers use sound vibrations to break up water into tiny droplets and propel those droplets into the air.


It’s all well and good to know about these different types of humidifiers, but which ones produce air pollution?

Certain Humidifiers Can Increase Indoor Air Pollution

Of the four main types of humidifiers, two (ultrasonic and impeller) have been found to contribute to indoor air pollution. While impeller humidifiers are less commonly used today, both types share a concerning trait: their method of dispersing water can also release pollution into the air.


When referring to air pollution in this context, I’m specifically talking about particulate matter: tiny physical particles that can be harmful when inhaled.


Ultrasonic and impeller humidifiers cause this issue because of how they operate. Unlike evaporative or vaporizer humidifiers, these models generate a fine mist by mechanically agitating water. This process does not distinguish between water droplets and the particles within them. As a result, any particulate pollutants present in the water, such as metals, minerals, or microorganisms, are launched into the air along with the mist. Then, according to a University of Alberta research study, the mist “evaporates quickly into the surrounding air, but the minerals and salts dissolved in tap water are left behind in the air as suspended PM.”

What You Can Do About It

Humidifiers can be a great way to add moisture to dry indoor air, improving comfort and even helping with respiratory issues. However, not all humidifiers function the same way or have the same effect on air quality. While evaporative and vaporizer models tend to keep particles contained, ultrasonic and impeller humidifiers can release fine particles, including minerals and microorganisms, into the air. If you're considering getting a humidifier, look at evaporative or vaporizer models. If you already have an impeller or ultrasonic type, it’s worth taking a few simple steps to minimize their impact on indoor air quality.


According to the U.S. EPA, there are a few steps you should take to reduce the air quality impact of ultrasonic and impeller humidifiers.


  • Use distilled or demineralized water instead of tap water to reduce the release of fine mineral dust into the air.

  • Empty and refill the tank daily to prevent microbial growth. Always wipe all surfaces dry before refilling.

  • Clean the humidifier every three days. Scrub off any scale or film and rinse thoroughly to remove all cleaning residues.

  • Keep indoor humidity between 30% and 50% to prevent mold, bacteria, and dust mite growth. Use a hygrometer to monitor levels.

  • Follow the manufacturer's instructions for operation and maintenance to ensure safe and effective use.

This article has been revised as of June 2025 for accuracy and freshness.

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