Tabletops are the smallest and lightest type of humidifier available, but they are suited only for smaller spaces. Console models have a larger capacity—and thus a larger storage tank—to generate enough water vapor for a small house. In-duct systems have automatic water-filling capability and require much less attention than portable models; they are the the ideal choice if you plan to humidify the whole house and have a forced-air heating system.
Remember, tank size is not as relevant as how much water it can evaporate in a given period of time and, more important, how much water is needed to be vaporized to attain the desired humidity level. After you determine the unit size you want based on the number of rooms you need to serve, keep these considerations in mind as you shop:
A portable model should be relatively easy to carry, fill, and clean. Also look for an easy-to-replace wick, simple controls, and a tank that will fit beneath faucets. Some portable models can be programmed to turn on automatically. Among tabletops, you have a further choice: an evaporative model, which uses a fan to blow air over a wet wick, or a warm-mist model, which uses a heating unit to boil water, then cool the steam. Factor in the noise
If quiet is a must, consider a warm-mist tabletop unit. All warm-mist humidifiers we tested quieter than evaporative models. Some of the units added little or nothing to background noise levels except mild boiling and hissing sounds. By contrast, comparably sized evaporative humidifiers generated 45 to 50 decibels on low settings, comparable to the noise from a small air conditioner, and more than 50 decibels on high settings.
For larger areas, consider buying a console model and placing it away from sleeping areas (remember, this type is noisier). The water vapor travels quickly through the air in your home and will still benefit remote bedrooms if doors remain open for air exchange. While you could alternatively buy several warm-mist tabletop models, that will cost more. All console models use evaporative technology, so if noise is an issue, either run your console several hours before bedtime and turn it off or use several warm-mist tabletop models. Obviously, the latter would at least double your cost. Clean humidifiers regularly
All humidifiers require some effort to clean and disinfect regularly to prevent mold and mildew. Humidistats are a must
Digital or dial-controlled humidistats control humidity levels and shut the humidifier off when the set level is reached. Without a humidistat, humidity levels can become high enough to form condensation on windows and other cold surfaces. Overhumidification can lead to mold and bacteria growth. Humidistats that display room humidity levels and humidity settings are best.
Also some humidistats aren't accurate or reliable. And most portable humidifiers won't let you set relative humidity levels below 30 percent. When outside temperatures drop below 20º F, even an indoor humidity level of 30 percent can lead to condensation on windows, doors or other cold surfaces. Be sure to lower the humidity level as outdoor temperatures drop. Consider operating costs
In-duct systems and other evaporative models performed best on this measure. The evaporative tabletop units in our tests cost about $5 to $37 per year to run, compared with warm-mist models, which cost about $50 to $85 per year to run. The console models we tested, which were all evaporative, cost about $20 to $28 per year to run. In-duct models, while the most expensive initially, are more efficient to run than most console models, costing about $2 to $28 per year, including filter changes. Water supply and quality
Some humidifiers produce a lower output with hard water. But you'll find tabletop, console, evaporative, and warm-mist humidifiers that perform well under those conditions. Hard water might create more maintenance to remove mineral-deposit buildup.
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