Ideally, indoor humidity should be 30 to 50 percent. But without humidification, that level can drop to 10 percent in winter, because cold air holds less moisture and dries even more as it's heated.
Today's humidifiers have improved over some earlier models, which spewed white dust in our tests. But tabletop and console models still require frequent maintenance. Minerals in tap water can cause an accumulation of scale, a breeding ground for bacteria. Parts of the humidifier need to be descaled regularly with vinegar and disinfected with bleach, and filters and wicks require periodic replacement. Note, too, that hard water might reduce some humidifiers' output and increase buildup of scale.
If you're not ready to commit to regular maintenance-and if your home has forced-air heat-consider an in-duct humidifier that's plumbed into the water supply and drainpipes. Such units don't need refilling, and their easy-change filter requires service only once or twice a year.
Choosing among the three major types of humidifiers-tabletop, console, and in duct-involves trade-offs in efficiency, noise, and convenience. Primary considerations include the size of the space you need to humidify and how much you're willing to spend.
These portable models cost the least and are fine for humidifying a single room, but their small tank requires frequent refills. Evaporative tabletops use a fan to blow air over a wet wick, while warm-mist models use a heating unit to boil water before cooling the steam. Evaporative models are much cheaper to run, but their fan is noisy.
Although console models are larger than tabletops, they can still be moved from room to room. Their large, powerful fan blows a strong air stream across water, generating lots of moist air. Since a console can humidify more than one room, it allows more options for unobtrusive placement wherever an electric outlet is available. A console's larger tank needs less frequent refills, but it's more cumbersome to handle. All console models use evaporative technology, which is noisy. If noise is an issue, run your console for several hours until bedtime and then turn it off, or use two or more warm-mist portable models.
These humidifiers are the ideal choice if you have a forced-air heating system and want to humidify the whole house. They tap into the air ducts and are plumbed into the water supply. Most are evaporative-bypass units, which blow air over a wet wick. Some emit a warm mist. Others are nebulizers, which use a spray technology-and which may produce deposits of white dust from minerals in the water. In-duct humidifiers are quiet and require minimal maintenance. They're also the least expensive to run: about $30 or so per year, compared with as much as $350 or more for four tabletop models. But they generally require professional installation.
Consumer Reports has no relationship with any advertisers or sponsors on MSN. Copyright © 2007-2011 Consumers Union of U.S., Inc. No reproduction, in whole or in part, without written permission.