Cool-Mist Humidifiers

Quiet, versatile ultrasonic humidifiers are most popular

If you use a humidifier all year, a cool-mist model (evaporative or ultrasonic) is the best choice. Because cool-mist humidifiers don't raise the room temperature or emit hot steam, they are a good choice for warm, dry climates.

There are three types of cool-mist humidifiers. Impellers force (impel) water into the air as a fine mist; however, we found no positive reviews for humidifiers of this type. Evaporative humidifiers soak up water into a wick and use a fan to blow the moisture out. As a result, these models can be noisy. Also, though the humidifiers themselves can be inexpensive, replacing their wicks or filters is an ongoing cost. Ultrasonic humidifiers use high-frequency sound to vaporize water. Some ultrasonic humidifiers can emit warm or cool mist, offering the best of both worlds. Users say one drawback of this type is that minerals dissolved in the water may be released along with the mist, forming a white dust on furniture. Many ultrasonic models come with demineralization cartridges to reduce this problem. We found more positive reviews for ultrasonic humidifiers than for any other type.

Air-O-Swiss humidifiers earn some of the best reviews we found. These ultrasonic humidifiers can produce warm or cool mist and are suitable for rooms up to about 600 square feet. The water tanks on Air-O-Swiss humidifiers are detachable and transparent (so you can keep an eye on the water level). A built-in humidistat allows you to adjust the humidity in the room to your desired level. These humidifiers come with a demineralization cartridge (*Est. $19), which needs to be replaced every two to three months (or more often with hard water). They also include a purifying hydro stick (*Est. $30), which should be replaced annually. (However, independent tests conducted by a major consumer organization found that the stick is not really effective at controlling microbial growth.)

AllergyBuyersClub.com names the Air-O-Swiss 7144 (*Est. $200) its best humidifier. It is also named as a "splurge-worthy pick" in the comparison tests conducted by the Good Housekeeping Research Institute, and it earns a score of 8 out of a possible 10 ("Excellent, with room to kvetch") from Wired magazine. User reviews for this humidifier on Amazon.com are mixed (as they are for virtually all humidifier models, regardless of price). Although most of the 60 or so reviews we found praised the Air-O-Swiss 7144's quiet operation, attractive design and adjustable humidity level, it earns its share of complaints as well.

Users' most common beef is that the 1.5-gallon tank is hard to refill; it must be flipped upside down and opened with a screwdriver (leaking all over the place in the process, according to several reviews). Also, many owners say the demineralization cartridge that comes with this machine does not really work to control white dust. Several recommend using filtered water rather than relying on the cartridge. Some users also say that the Air-O-Swiss 7144, with its 3-gallon output, cannot really humidify a 650-square-foot room, as its manufacturer says. Others note that its digital humidistat isn't very accurate. One other humidifier in the Air-O-Swiss line, the Air-O-Swiss 7135 (*Est. $165) , gets similar reviews, but with this model we also saw several complaints about leakage.

For smaller rooms (up to 500 square feet), the Sunpentown SU-4010 (*Est. $80) earns excellent ratings across the board in one independent test and is also highly rated by AllergyBuyersClub.com. Like the Air-O-Swiss 7144 humidifier, it is designed to produce cool and warm mist, with variable humidity levels. However, this model does not include a humidistat. It does have a demineralization cartridge (called the Ion Exchange Filter), which should be replaced every six months. Other features include overheat protection and a split rotating nozzle to direct mist in two directions simultaneously. This model is energy efficient (using up to 43 watts on the cool-mist setting and 90 watts for warm mist) and very quiet.

Owners posting reviews to Amazon.com say the Sunpentown SU-4010 produces plenty of good, fine mist, and it is easy to fill and maintain. Its compact design is also a plus, and it receives fewer complaints about white dust than most ultrasonic humidifiers. However, we saw more reliability complaints for this humidifier than we did for the more expensive Air-O-Swiss models. We saw reports of humidifiers breaking down anywhere from a week to four months after purchase, and we also read several reports of leakage, often severe. A couple of users consider this humidifier to be a safety hazard, as water leaks could get into the wiring, though we read no actual accounts of shock or fire problems.

A less expensive alternative for small rooms is the Crane EE-5301 Cool Mist Humidifier (*Est. $45) . This small tabletop humidifier has a 2.3-gallon output and can humidify a 250-square-foot room, but it has only a 1-gallon tank. It has variable mist output, an automatic shutoff feature and a 360-degree rotating nozzle to direct the mist. Although this humidifier has not been evaluated in any professional tests, it gets strong recommendations from more than 1,000 users posting reviews to Amazon.com, Walmart.com, Target.com and Viewpoints.com.

Users say this Crane humidifier performs well and is very quiet. They also appreciate the lack of expensive filters or cartridges. Most find the EE-5301 easy to clean and fill, but others say this humidifier is hard to clean and it's awkward to fill the tank from the bottom. Its small tank is another cause of complaint; it holds a little less than 1 gallon, and at maximum output it must be filled several times a day. Users also complain of white dust buildup with this model, and several recommend using filtered or distilled water to eliminate the problem. We found a few reports of breakdowns, but no more than for most humidifiers. This humidifier is cool-mist only; it can't double as a warm-mist humidifier.

Another tabletop humidifier that gets generally good reviews is the Safety 1st Ultrasonic 360 (*Est. $30) . This small humidifier offers adjustable output, with two rotating nozzles to direct the mist, and it can humidify an area up to 330 square feet. Although it does not include any sort of filter or antimicrobial technology, one independent test finds that it nonetheless does a better than average job of keeping bacteria under control. It also produces excellent mist output and is easy to use. It automatically shuts off once the tank is empty.

We found about 125 reviews for the Safety 1^st Ultrasonic 360 at Target.com (and another 25 or so at Amazon.com, where it is no longer sold). Users say this humidifier produces good mist output and is very quiet, and they appreciate its adjustability. We did not see many complaints about white dust, despite the lack of a demineralization cartridge. However, we did find several complaints about durability and leakage, and one user reports getting a shock when water leaked into the machine's motor. A few owners also complain that the humidifier can be knocked over easily.