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.
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