Evaporative cool-mist humidifiers use a fan to blow air through a wet wick; the air cools as it picks up moisture from the wick. Periodically, you’ll need to replace a filter or wick, which can run from $10 to $20.
Ultrasonic cool-mist models—the majority of units in CR’s ratings—use small vibrating diaphragms called nebulizers to create a mist. Ultrasonic units typically are less noisy than evaporative models because they have no fan. But their mist can leave a white dust—tiny particles of mineral precipitate—on surfaces. (To prevent that dust, you can use distilled or filtered water instead of tap water.)
Help for stuffy noses: Cool mist can help shrink swelling in nasal passages, making breathing easier, according to the Food and Drug Administration. By contrast, warm mist can cause nasal passages to swell, making breathing more difficult, another reason the FDA doesn’t recommend their use for infants with coughs and colds.
Convenience in small sizes: In our ratings of small humidifiers, cool-mist models were judged more convenient as a whole vs. small warm-mist units—better known as vaporizers—reflecting factors such as ease of operation. Several small cool-mist units in our ratings have humidistats, which turn off the unit when the air reaches a set humidity level; none of the small vaporizers in our ratings have that feature. Small vaporizers typically don’t even have a power switch; they start working when you plug them into an outlet. (They do, however, shut off automatically when the tank is empty.)
More shopping choices: Cool-mist models make up more of the portable humidifier market than other types, says Marion Wilson-Spencer, a market analyst who covers humidifiers for Consumer Reports. In CR’s ratings, you can find cool-mist humidifiers in every size we test, including travel models, units for small, medium, and large rooms, and consoles for very large rooms of 1,000 square feet or more. In our ratings, you won’t find warm-mist units in travel or console sizes; you also won’t find dual-mist units in small, medium, or travel sizes.
