Summary. There are a variety of humidifiers available that utilize primarily three different mechanisms for delivery of water mist: wicking, steam, cool mist, and ultrasonic. This article provides a quick introduction to these three types of technology.

Proper Placement. For best use, humidifiers that produce visible steam or mist should be placed on a high surface. This allows for a sufficient distance to allow the steam or mist to become absorbed into the ambient air. Any cold surfaces will cause the steam or mist to condense quickly rather than being absorbed into the air. This will result in surface moisture rather than an increase in humidity.

Wicking Humidifiers. Wicking humidifiers cause water to run over an evaporative surface. There are several drawbacks to wicking humidifiers:

  • Expensive Filters. The cost of regularly replacing filters is a drawback to wicking humidifiers. Some systems are advertised as having permanent washable filters. These will require regular maintenance, and if a filter ever gets too dirty to clean, a replacement may be costly and difficult to find.
  • Slow. Unlike steam and ultrasonic humidifiers, the wicking humidifiers depend on the natural drying capabilities of the ambient air. The technology is similar to that of hanging several wet towels up in the room and having a fan blow on them to dry them out (thereby transferring the moisture into the room). If you’ve ever tried drying clothes indoors, you know that it takes a while for the clothes to dry even if a fan is blowing on them. Similarly, wicking humidifiers can take a while to transfer humidity into the air.
  • Noisy. To be effective, wicking humidifiers rely on fans and water running down a honeycomb or webbed filter. The fan and running water can produce quite a bit of noise.

Steam Humidifiers. There are several drawbacks to wicking humidifiers:

  • Dirty. If not cleaned regularly, steam humidifiers can develop deposits of slime in the water reservoir. These slimy deposits may have a brown color to them. The collected dust along with warmth, moisture, and darkness become an ideal breading ground for bacteria, mold, fungus, mildew, and spores.
  • Hazardous. Burns from hot steam are perhaps some of the worst. The steam emitted from a steamer can be dangerous to touch.
  • Wet. Steam tends to consist of fairly large particles of water. If placed near a cold window, condensation could easily result in a puddle of water.
  • Difficult to Control. There is no such thing as “kind of boiling.” Water is either boiling or it isn’t. Once a steam humidifier is producing steam, it is difficult to regulate the amount of steam produced. If steam is produced too quickly, it turns into moisture or wetness on surfaces rather than humidity in the air. This is like what happens to a cloud when rain starts falling.
  • Electrical Consumption. Boiling water requires sufficient electricity to heat the water. The electric usage is likely higher than that of some other humidifier technologies.

Cool Mist Humidifiers. Also known as impeller humidifiers, these units produce mist by a high speed spindle immersed in water. As the spindle turns, a mist is created and then blown by a fan into the room. Because these humidifiers don’t boil water, they are cooler and safer to touch. There are several drawbacks to cool mist humidifiers:

  • Wet. The mist created by a impeller humidifiers tends to have fairly large water particles. This produces considerable moisture and wetness on surfaces rather than humidity in the air.
  • Noisy. Combining a high speed spindle in water with a fan mechanism produces a significant amount of noise.

Ultrasonic Humidifiers. The ultrasonic humidifier systems use a very fast vibrator in a shallow water reservoir to generate a mist that naturally rises upward. There are many benefits to these units:

  • Quiet. These are perhaps the quietest humidifiers available.
  • Effective. Because the vapor created by these units is so fine, it is rapidly absorbed into the air rather than resulting in wetness and moisture on surfaces.
  • Clean. Because these units require no wicking fabric and no boiling water, they are fairly clean in operation. Because the water vapor is taken quickly into the air, any particulates in the water that are left behind will be visible on surfaces. Therefore, it is best to use filtered or distilled water.
  • Dusty Residue. There may be dusty residue left on surfaces in a room where ultrasonic humidifiers are used. This can be a nuisance to keep clean.
  • Potential Pulmonary Respiratory Bronchial Hazard. Depending on the water used, most ultrasonic humidifiers produce a fine powdery layer of mineral deposits and other impurities on surfaces in the room where they are used. It is logical to assume this fine powder also makes it into a person’s lungs. Because lungs typically do not respond well to fine powdery substances, it is reasonable to conclude that ultrasonic humidifiers may be harmful to the human respiratory system. Mineral dust itself is not usually a hazard. If minerals are found in water, it is considered beneficial. If mineral dust is breathed into the lungs, it could be hazardous.

Humidifier Resources

Video. Below is a video by Gregory Johnson explaining how to more effectively humidify your home while at the same time reducing power usage. In the video, Gregory uses the Kill-A-Watt power meter.

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