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The best humidifiers work by pumping moisture into dry indoor air, delivering a flurry of benefits, from relieving irritated skin, chapped lips and sore throats to preventing wood floors from cracking. "Excessively dry air also puts stress on the mucus membranes, making them more susceptible to allergens and other airborne irritants," says Dr. John McKeon, a former ER doctor and CEO of Allergy Standards, an independent asthma- and allergy-friendly certification company.
If the relative humidity in your home gets down around 30%, the experts at the Good Housekeeping Institute recommend using a room humidifier. (A digital air monitor, like the Airthings View, a winner in our 2022 Home Reno Awards, can help you get a read on humidity levels in your home.) However, not all humidifiers work their magic in the same way. Through continuous testing of these types of devices dating back decades, our experts have gotten hands-on with two main types of humidifiers: cool-mist humidifiers and warm-mist humidifiers.
Here, we compare the pros and cons of each type of humidifier, breaking down the main differences and explaining which option is better to use for coughs and congestion, as well as which is the best type of humidifier for babies.
Benefits of warm mist humidifiers
Better at reducing bacteria and germs
Quieter than cool mist options
Warms cooler winter air
Generally less expensive than cool mist humidifiers
Hot steam can pose a safety hazard for children and pets
Might cause nasal passages to swell, so not ideal for colds
Higher energy consumption
Also known as vaporizers, warm mist humidifiers have been on the market the longest and they’re often the least expensive. The mechanics are simple: an internal heating element boils water, which in turn releases steam into the room. The high temperature reduces the growth of bacteria and germs, plus they don’t make a lot of noise. Since humidifiers are typically used in winter, the warm mist of air can be nicer than a cold one, too.
The major downside of warm mist humidifier is that the hot water can present a burn hazard, for example if the machine were to leak or tip over. That’s why our experts don’t recommend them in homes with small children or pets. Though it might go against what you were told as a kid, warm mist humidifiers can also cause nasal passages to swell and make breathing more difficult, according to the Food and Drug Administration. So they’re not ideal for the treatment of colds. One final drawback: warm mist humidifiers use more energy to boil water.
Benefits of cool mist humidifiers
Safest for use around kids and pets
Can be used year-round
More energy-efficient than warm mist models
Particularly effective at helping with colds and coughs
Can accumulate bacteria growth more easily
Fan technology can be louder than warm mist options
For starters, most units sold today are cool mist humidifiers, so you’ll have a lot more choice. The absence of any burn hazard makes them safe to use, even around babies. They’re also more effective in the treatment of colds because they can shrink nasal passages.
One drawback is that cool mist humidifiers are a bit noisier, which can be an issue for light sleepers — plus, the cool mist of air isn’t ideal during cold weather months. But the major downside is that cool mist humidifiers can accumulate bacteria growth more easily if they're not maintained properly. While they're fairly easy to clean, you will have to remember to regularly clean your humidifier to prevent bacteria and mold growth.
Our humidifier testing covers two types of cool mist technology, evaporative and ultrasonic, which each have their own pros and cons that you'll want to keep in mind, too:
✔️ Evaporative cool mist humidifiers use a fan to draw air through a wet wick (or wick filters) and then release the vapor into the air. "Our tests have found that they're less likely than most cool mist humidifiers to cause mold or mildew growth in the room because they don’t lead to over-condensation on floors or surfaces," says Dan DiClerico, Director of Home Improvement & Outdoor at the Good Housekeeping Institute. However, upkeep is a bit arduous as you must replace the wick or filter regularly to prevent bacteria growth in the device.
✔️ Ultrasonic cool mist humidifiers use a high-speed vibrating plate to turn water into a fine mist. With smaller fans and no gurgling water, these are often the quietest option when it comes to cool mist humidifiers. Cleaning is also relatively simple (just rinse the tank and internals), but you do need to keep these raised off the ground to avoid puddling of the water.
So, which is better: A cool mist or warm mist humidifier?
Bottom line: Warm and cool mist humidifiers are equally effective at adding moisture to the air in your home, so both are helpful at relieving dry skin and cracked lips, and also reducing static electricity around the house. Cool mist models are particularly good at easing respiratory and sinus discomfort associated with colds and coughs. If you have children or pets, our experts also recommend opting for a cool mist option, since they pose zero burn risk.
Can't decide? Opt for a humidifier that combines both warm and cool mist options, like GH Institute favorite Levoit Ultrasonic Humidifier. Also known as dual mist humidifiers, these types of models allow you to switch between your preferred mist option, depending on the season and your needs. In addition to offering both mist options, the Levoit Ultrasonic has a large water tank capacity that makes it easy to fill, plus it's quiet while running throughout the night and it can connect to an app, Amazon Alexa or Google Assistant for remote and hands-free controls.
But whichever method you choose, our pros want to emphasize the importance of not overdoing it. Make sure you are properly regulating the output of your humidifier, because setting it at too high humidity levels can cause harmful bacteria or mold to grow, leading to a new host of problems.
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