Are Humidifiers a Good Idea for Beating Dry Air?

One of the less enthralling aspects of cold weather is dry indoor air. Interiors tend to be overheated, and humidity may drop as low as 10 percent. Adequate humidity is 25 to 50 percent, the range where people feel comfortable. Many people combat dryness with a humidifier. Here's what a humidifier can do—not all of it good.

What's Good About Humidifiers

Adequate humidity can help prevent or alleviate dry skin, dry eyes, and irritated nasal passages. And since you feel warmer in warm humid air than in dry, you can keep your thermostat lower, which also helps prevent dry skin.

A humidifier can also ease symptoms of a cold, sore throat, or cough. Cold dry air dries mucus, making it harder to clear from your nasal passages. Moist air helps loosen it.

Whether proper humidity can prevent colds is hard to say. Some experts think that dry air irritates nasal passages, making you more susceptible to colds. People with asthma often find it more difficult to breathe dry cold air, which a humidifier can help address.

What's Not So Good About Humidifiers

If not kept very clean, humidifiers can be a source of indoor air pollution, microbes and allergens. If your water contains contaminants, the humidifier will spray them into the air. Unfortunately, in spite of some recent design improvements, humidifiers are still generally hard to keep clean.

Overuse can be problematic as well. Very high humidity (over 60 percent) can provide a good environment for viruses and bacteria. And it promotes the growth of mold, which can cause allergies in sensitive people.

Aside from these health concerns, there are financial ones to consider: The cost of running a humidifier—anywhere from $30 to $85 a year—often exceeds the price of the unit itself.

The sound of a humidifier is sometimes enough for people to pass on their use; some models can emit irritating noises.

Humidifier Types and Models

If you decide that you want to try a humidifier, there are many options from which you can choose. You can spend $20 on an inexpensive table model or up to $500 on a floor model (console). Here are the four general types of portable humidifiers:

  • Evaporative humidifiers: These are the most common kind. Water is absorbed by a wick filter and sent into the air by a fan. Some have a moving belt in a tank of water.
  • Steam humidifiers or vaporizers: Often the cheapest, they turn water into steam, thus killing microorganisms. They pose a risk of fire and scalding and thus are not recommended if you have small children or pets. The minerals from the water can clog the machines.
  • Cool-mist humidifiers or impellers: Water is pumped upward from a tank and "impelled" against fan blades, which disperse it in the air.
  • Ultrasonic humidifiers: These use high-frequency vibrations to turn water into mist.

Keeping Your Humidifier Clean

Before you use your unit for the first time, clean it. Afterward, never put it away without cleaning it following the manufacturer's instructions.

Using tap water in a humidifier is usually not a good idea, because the minerals in it may be dispersed in the air as white dust. Minerals may also appear as a crusty deposit inside the humidifier, which is a surface on which bacteria and mold can grow.

One option is to use demineralized water. Some models come with demineralizing filters, but these have to be frequently changed and are expensive.

Here are some humidifier guidelines:

  • Under 5 gallon capacity: Clean every day—that is, empty the tank, wipe dry, and refill. Sanitize every 7 days, as follows: empty and refill with a solution of bleach (1 teaspoon of bleach to 1 gallon of water). Soak for 20 minutes and rinse. Brush away mineral deposits and rinse again with a 50 percent solution of vinegar.
  • Larger than 5 gallon capacity: Empty every day and refill with clean water. Every third day, clean surfaces with hydrogen peroxide or vinegar (to kill molds). Every two weeks, sanitize with bleach, following the instructions above.
  • Though some newer models claim to have antibacterial features, microbes can still grow, and you still need to clean the humidifier regularly.

And keep in mind

  • Your humidifier will do a better job if your house is well insulated and has a vapor shield (that's an impermeable layer on the inner side of the insulation).
  • If somebody in your home is allergic to mold or dust mites or has asthma, talk to your doctor before using a humidifier.
  • When you're not using the humidifier, leave it clean and empty.
  • To make sure that the machine is doing a good job and not making the air too humid, buy a hygrometer, which measures moisture in the air. A digital wireless model costs about $20. Many humidifiers now come with a built-in hygrometer, called a humidistat, that automatically switches the machine on and off. But these are not always accurate or reliable.
  • If you have forced-air heat in your home, you can add a humidifying unit to the system to humidify the whole house. These do not pollute the air and are almost maintenance-free—you may have to change the filter occasionally. Central units may cost $300 or more, plus installation, but are inexpensive to run.

    Source: Originally published in The University of California, Berkeley Wellness Letter (January 2011)

    Publication Review By: the Editorial Staff at HealthCommunities.com

    Published: 03 May 2011

    Last Modified: 22 Jan 2015