Humidifiers: What To Look For

Types of Humidifiers

If the atmosphere in your house is drying out your throat and nasal passages and impairing your natural defenses against viruses, a humidifier can do you a world of good. Humidifiers are particularly helpful in the winter, when forced hot-air heating systems contribute to the problem. Even wood furniture, floors and structural beams can begin to dry out and crack as a result of excessively dry air. A bit more humidity, particularly warm mist, can also help you control heating costs by making the air feel warmer.

Portable humidifiers can be found in two basic styles. Small tabletop models can humidify a room or two, and can easily be carried from place to place as needed. Console humidifiers are about the size of a laundry hamper, and depending on their capacity can humidify an entire house or apartment. They're often fitted with casters to make them easier to move around.

The purpose of any humidifier is to put water into the air, but it can accomplish this in a number of different ways.

The most common type of humidifier is evaporative. Evaporative humidifiers are among the most energy efficient, and their filters help keep microorganisms and minerals in the water from being dispersed into the air. The filters themselves can be prone to breeding bacteria unless they are meticulously maintained; studies indicate that owners generally fail to do this chore. Most modern humidifiers are designed to address this problem by incorporating antibacterial filters, special plastics and a construction that prevents stagnant water from accumulating around the filter, but cleaning is still required.

While you can find very cheap humidifiers at your local bargain store, they're mostly impeller models, which we didn't include in this report. Impeller humidifiers tend to disperse microorganisms into the air; they also disperse the minerals dissolved in the water, which settle as "white dust" onto your furnishings. To prevent this, you have to fill them with distilled or de-mineralized water, so there goes the money you saved up front. Experts say it's better to spend a bit more now to save money later and, more importantly, to avoid possible health hazards.

Ultrasonic humidifiers, which use high-frequency vibrations to drive water into the air, are becoming more popular. The main advantage of this type of humidifier is that it is very quiet, because it doesn't use a fan to evaporate water. Most ultrasonic models don't use a filter, although they do have an optional demineralization cartridge that needs to be replaced every few weeks. This cartridge helps prevent white dust, but it isn't 100 percent effective.

Of the various types of humidifiers, each has advantages and disadvantages, and the type you choose will depend on how and where you'll be using the humidifier. You should also consider how willing you are to clean and maintain the unit, although all types of humidifiers require some cleaning. ConsumerReports.org advises considering a warm-mist tabletop unit if quiet operation is your first priority, but notes that these humidifiers tend to cost more to run (about $50 to $85 per year). Evaporative tabletop models cost between $5 and $40 per year to run, but the tradeoff is that they can be noisy.

Cool-mist humidifiers are safer because they don't heat water -- minimizing the risk of accidental scalding. Evaporative humidifiers can take up to six hours to raise the humidity level in a room, while warm-mist humidifiers usually produce faster results. Warm-mist models also produce steam, meaning they can raise the air temperature in a room. That's handy for the winter season, but not so useful if you live in warm climate.

Humidifier shopping tips

More humidity isn't always better, which is why experts say it's important to get a humidifier you can set at the appropriate level (about 30 to 50 percent is the comfortable range in most situations). One way to tell that an area is over-humidified is that condensation will appear on the interior window surfaces. Too much humidity can promote the growth of mold, mildew and dust mites. If your home is more than 50 years old, it probably doesn't have a vapor barrier built into its walls; in this case, excess moisture from inside the house can condense on joists and studs, eventually causing rot and predisposing them to attack by insects.

Here are some other factors you'll want to consider before purchasing a humidifier:

• You should determine whether the stated output of the humidifier corresponds to the area you want covered. Estimate a bit on the high side if your house tends to be drafty, and keep in mind that most humidifiers only work well in a single room or in adjacent rooms with the doors open.

• Pay attention to the size of the tank. While an 8-gallon humidifier will humidify a large area, you'll have to refill it frequently if it only has a 1-gallon tank.

• An adjustable humidistat measures the humidity in the room and adjusts the output of the humidifier to maintain the set value. Watch for humidifiers that have the on-off switch combined with the humidistat controls. This is less convenient because the desired humidity must be reset each time the unit is operated.

• An automatic shutoff prevents the humidifier from running when the reservoir is dry. A reliable automatic shutoff is especially important in warm-mist models, which can overheat and catch fire if they continue running while dry.

• Indicator lights alert the user when water is low or the filter requires maintenance.

• A higher-speed fan humidifies faster; a lower-speed fan reduces noise. Look for a unit with an adjustable fan speed.

• A removable reservoir makes refilling and cleaning more convenient. Dishwasher-safe reservoirs make for the easiest cleaning. Other helpful features include a wide opening and/or refill hose and carrying handles. Console humidifier reservoirs, which hold much more water, are more conveniently removed if they are divided into two or three sections; the unit itself should have casters, so it can be moved easily.

• Anti-scalding features are important for vaporizer and warm-mist models. Safety latches are most common.

• Anti-white dust cartridges are usually included in impeller and ultrasonic humidifiers. These minimize dust caused by the minerals left behind by tap water and must be replaced every few weeks -- more often if you have hard water.

• Some humidifiers offer antibacterial features. These include antibacterial filters, antibacterial plastic used in construction and/or a design intended to eliminate pockets of stagnant water around the filter.