Warm-mist humidifiers can make a room feel warmer, allowing you to bump your thermostat down a notch or two without feeling cold. Because warm-mist humidifiers boil water before expelling it into the air, they kill the bacteria that can breed in a humidifier's tank, and they don't require the ongoing expense of filters that must be changed. These models are also quieter than fan-driven evaporative humidifiers. There are, however, some drawbacks. They tend to have poor energy efficiency, and minerals from the water can build up on the machines heating plate, requiring periodic cleaning. Plus some experts warn against the use of these machines near children, where curious hands can tip over a humidifier filled with hot water. These models are not recommended for people with asthma, because hot or warm mist can irritate breathing passages.
Models that produce warm mist are generally cheaper than those reviewed previously that produce both cool and warm mist, but they do not fare nearly as well in reviews. We found the strongest recommendations for the Vicks Warm Mist V745A (*Est. $30). Users appreciate the low price, minimal noise and light weight, and say that it will run all night on a full tank. Several note that mineral buildup can occur and recommend vinegar for this purpose.
We also saw more durability complaints for the Vicks Warm Mist V745A than we did for most cool-mist models. Some owners report breakdowns within weeks or even days after purchase. Leakage is another common problem. In professional tests, this humidifier comes in at the bottom of the pack. Its moisture output and ease of use are acceptable but not great, and it gets very low scores for energy efficiency.
The only other warm-mist humidifier to earn any positive recommendations in our sources is the Holmes HM5305-UC (*Est. $35). In humidifier tests by the Good Housekeeping Research Institute, this model is the quickest at raising the humidity in the testing room, but it also uses the most electricity of all the models tested. Editors also quibble with the fact that its humidistat has manual dial controls rather than digital ones. We found many complaints about its durability. In addition to the usual problems with leakage, many owners report that the heating element actually warped or melted the water tank. Another drawback? The tank can be difficult to fill.