Bests & Worsts Reviews from Amazon

Humidifiers can be placed into 4 categories based on how they generate vapor: evaporative, ultrasonic, steam, and impeller. It took me a little while to figure out what I wanted, so hopefully I can save others some time by summarizing what I found. Evaporative humidifiers move air over water, usually with an absorbing "wick" or spinning disks, for an accelerated version of the natural evaporation process. Electricity is used only to run a fan or other rotating element, so evaporative humidifiers are the cheapest to run. The physics of evaporation lead to two qualities: They are self regulating, as the water will cease evaporating once the air is saturated, and they have a slight cooling effect. The rate of humidity pumped out is relatively low. The wicking medium - usually a corrugated paper or paper/cloth material - can harbor mold, so you must change the water regularly and avoid letting the water stand around. The fans vary in noise level. Example: Vornado Whole-Room Evaporative Humidifier, HU1-0021-28 Ultrasonic humidifiers use a membrane vibrating at high frequency to atomize water molecules. The vapor output is high and the machines are the quietest of all humidifiers. Their energy usage is middle-of-road: more than evaporatives, and less than steam-based. The main drawback of ultrasonics is that the vibrating membrane atomizes not just water, but also anything else in the water - microorganisms, and particularly minerals, which may appear as a "white dust". This is a big con for allergy sufferers, so many units include replaceable demineralization cartridges and water filters to eliminate microorganisms and minerals before they get atomized. You can use keep replacing these cartridges, or keep buying distilled water, making ultrasonics rather costly. The vapor will be the temperature of the water - which is to say cool, unless you choose a unit with a heating element. Example: SPT SU-4010 Ultrasonic Dual-Mist Warm/Cool Humidifier with Ion Exchange Filter Steam humidifiers heat water to the boiling point until they, well, boil and produce water vapor. Any microorganisms will be killed, and any minerals are left behind in the water reservoir, making steam humidifiers excellent for allergy sufferers. The left-behind minerals can be significant if your water is dirty, so these units must be cleaned regularly (rinsed out every couple days, and a vinegar soak one a week). Alternatively, you can use distilled water. Energy use on steam humidifiers is highest, usually around 200-300 watts, as they must heat the water. The vapor coming out will be hot - good for winter colds and flus, but also a small concern for those with small children. Impellers are kind of a cross between evaporatives and ultrasonics. They pass water at high speed through the air, making them similar to evaporatives, but they do so with enough mechanical force that other particles are atomized as well, imparting the same problems of white dust and microorganisms. Example: Sunbeam Health 645-800 Cool Mist Humidifier I needed strong humidification, so it was a choice between steam and ultrasonics. I was wary of the ultrasonics because I would have to live with white dust, or keep buying either cleaning cartridges or distilled water. They also tend to be the costliest humidifiers. So I chose this ~$30 Vicks steam humidifier, which does the job well and produces plenty of clean vapor. My water is pretty dirty and an unsightly crust builds on the heating element after a few days of constant use, but I'm glad it's in there and not in my lungs. The water volume is on the small size, but this has the advantage of being damage control when/if it springs a leak someday. Another category to consider, by the way, are air washers, which usually combine an impeller design with electrolysis of water to both clean and humidify air. The humidification level is similar to evaporative and impeller designs, so they weren't for me. Example: Sanyo ABC-VW24 Air Washer Air Purification System with Electrolyzed Water Technology