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How Humidifiers Work

Types of Humidifiers

There are many different ways to raise the humidity in your home. For example, you can put a pan of water on the stove or on the radiator, or you hang wet towels near a heater duct. But most people use a mechanical humidifier to do the job. Here are the four most popular technologies:
  • Steam

    KAZ V150 steam vaporizer
    Often referred to as a "vaporizer," a steam humidifier boils water and releases the warm steam into the room. This is the simplest, and therefore the least expensive, technology for adding moisture to the air. You can find inexpensive impeller models for less than $10 at discount stores. Another advantage of this technology is that you can use a medicated inhalant with the unit to help reduce coughs.

  • Impeller

    KAZ V400 impeller humidifier
    In this humidifier, a rotating disc flings water at a comb-like diffuser. The diffuser breaks the water into fine droplets that float into the air. You normally see these droplets as a cool fog exiting the humidifier.

  • Ultrasonic

    KAZ 5520 ultrasonic humidifier
    An ultrasonic humidifier uses a metal diaphragm vibrating at an ultrasonic frequency, much like the element in a high-frequency speaker, to create water droplets. An ultrasonic humidifier is usually silent, and also produces a cool fog.

  • Wick/Evaporative System

    KAZ V3500 evaporative humidifier
    The wick system uses a paper, cloth or foam wick or sheet to draw water out of the reservoir. A fan blowing over the wick lets the air absorb moisture. The higher the relative humidity, the harder it is to evaporate water from the filter, which is why this type of humidifier is self-regulating -- as humidity increases, the humidifier's water-vapor output naturally decreases.
Here are some things to keep in mind as you are weighing the advantages and disadvantages of the different technologies:
  • Steam vaporizers can be dangerous around children because they can cause burns. They also have the highest energy costs. However, there are no bacterial or mineral concerns with this technology.


  • Impeller and ultrasonic designs have low energy costs but raise two concerns. First, if the water gets stagnant, these designs will spray the stagnant water, and any bacteria it contains, into your home. This is why it is important to clean the tank regularly and refill it with clean water when you haven't been running it. Many high-end ultrasonic units therefore have antibacterial features built in. For example, some units use ultraviolet light to kill bacteria.

    The second concern is minerals in the water. Impeller and ultrasonic designs send these minerals into the air. If the water in your area contains a lot of minerals, you will notice them as dust. The EPA does not issue health warnings about minerals in the air, but does recommend using low-mineral water (such as distilled water) in your humidifier. Many ultrasonic models feature a demineralization cartridge that filters minerals out of the water to prevent the dust.


  • Some humidifiers monitor the relative humidity of the air and will turn on and off as appropriate to maintain a preset level.


  • Humidifiers can be installed as small portable room units, or they can be integrated into your furnace for full-house humidity control.

If you are interested in tracking your home's humidity, an inexpensive hygrometer will show you the relative humidity in your house. You may be surprised to learn how low it is!

For more information on humidifiers and related topics, check out the links on the next page.



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