Cool vs. Warm Mist Humidifiers

It might not be the first thing that springs to mind when you picture the ideal sleep environment, but optimal indoor humidity levels go a long way in supporting comfort and overall well-being. According to the Environmental Protection Agency (EPA), indoor humidity should be between 30 and 50 percent. That helps keep airways properly hydrated, which can reduce snoring, ease congestion, and prevent nighttime coughing so you can sleep soundly.

A humidifier can do the trick nicely, but what’s better — cool mist or warm mist humidifiers? While both kinds effectively raise humidity levels, the best humidifier often comes down to your climate, home environment, and personal preference. Here’s how to decide which is right for you.

What Is a Cool Mist Humidifier?

As the name suggests, a cool mist humidifier pushes room-temperature moisture into the air. There are two types of cool mist humidifiers:

• Evaporative humidifiers have a fan that blows air through a wet filter or wick. The water then evaporates, bringing moisture into the room. This kind of humidifier is self regulating, since a dry room will pull more moisture through the filter. As the air becomes more humid, evaporation naturally slows down. That helps keep a room from becoming too humid. Like insufficient humidity, high humidity can make it harder to breathe comfortably at night. It can also trigger sneezing or coughing, and it makes it harder for the body to cool itself down. Plus, high humidity can negatively affect sleep stages.
• Ultrasonic humidifiers use high-frequency vibrations to break water droplets down into an incredibly fine mist, which is then dispersed into the air. This type of humidifier tends to be more energy efficient than evaporative humidifiers because it doesn’t need a fan, which also makes it quiet.

Cool mist humidifiers don’t have a heating element, so they’re pretty energy efficient in general, especially compared to warm mist humidifiers. That also makes them a good fit in kids’ bedrooms, because there’s no concern over burns or scalding. Cool mist humidifiers can cover a large area, so they work well in bigger bedrooms and living spaces.

On the other hand, cool mist humidifiers aren’t great in colder climates or colder months of the year. Since they don’t warm the air, they can make a room feel noticeably colder — not ideal in cold weather. You’ll also need to commit to regular cleaning to keep buildup from bacteria and mold accumulating in the tank, especially if you’re filling it with tap water.

What Is a Warm Mist Humidifier?

Warm mist humidifiers are equally self explanatory. They use a heating element to boil water and then release the warm vapor into the air. That makes them soothing and cozy, especially in colder months. They don’t need a fan, so they’re usually the quietest humidifier you can get. And as a happy bonus, the heating process can help reduce bacteria in the water before it’s dispersed into the room. But that doesn’t make warm mist humidifiers germ-free, so you’ll still need to clean them regularly.

On the downside, this type of humidifier does use more energy because of the heating element. And because they get hot, they can pose a burn risk (particularly to young children and pets, who tend to be more curious). Finally, coverage areas for warm mist humidifiers are more limited than cool mist units. If your bedroom is large or has very high ceilings, a cool mist humidifier might be more effective for maintaining optimum humidity levels.

Key Differences Between Cool and Warm Mist Humidifiers

Understanding what distinguishes cool mist and warm mist humidifiers can help you decide which one will work best in your bedroom. Here’s how they compare. 

• Mist temperature. The clue is in the name — cool mist humidifiers push moisture that’s room temperature, while warm air humidifiers release heated vapor. Depending on where you live and the time of year, one may be far more appealing than the other.
• Noise levels. Warm mist humidifiers don’t need a fan to work, so they’re typically the quietest option. Ultrasonic cool mist humidifiers are also really quiet, while evaporative cool mist models have a fan that usually emits a low hum.
• Energy use and cost. The most energy-efficient option is an ultrasonic cool mist humidifier, but evaporative models are a close second. Since warm mist humidifiers have a heating element, their energy consumption is a little higher.
• Reach. The fan in cool mist humidifiers, especially evaporative models, means they can cover large rooms more effectively than warm mist humidifiers.
• Suitability for children and pets. The biggest safety issue with a humidifier comes down to the heating element, which can pose a burn risk if the unit is touched or tipped over. If you live in a home with curious kids or pets, a cool mist humidifier is the safer choice because it doesn’t get hot (and neither does the mist).
• Maintenance and cleaning needs. There’s no way around it — if you have a humidifier, you’ll need to clean it regularly. But cool mist humidifiers typically need more frequent cleaning to keep mold and bacteria at bay. If you live in an area with hard water, keep in mind that some ultrasonic models can also produce what’s known as “white dust,” which is mineral residue. It can settle on surfaces near the humidifier, so you may need to do a little more cleaning than usual. Using distilled water can help, or look for an ultrasonic cool mist humidifier with a filter.

Which Type Is Better for Sleep?

Both cool mist and warm mist humidifiers can be effective for improving your sleep, especially if you live in a dry climate. But sleep is personal, so one type of humidifier may be a better fit for you specifically. Here’s what to consider.

Situational Recommendations

If you live somewhere hot and dry, a cool mist diffuser will help push more moisture into the air without raising the room’s temperature. In cold, dry winter months, however, a warm mist humidifier that adds a little warmth to your bedroom may be really appealing. Warm vapor can also help ease congestion from colds.

From a safety perspective, cool mist humidifiers are a better choice in nurseries or kids’ bedrooms because they eliminate the potential for burns or scalds. If you’re considering using a humidifier in a kid’s room to help with cold symptoms like a stuffy nose, look for a model that has built-in safety features, like a cool-touch exterior, a locking lid, and an automatic shut-off feature if it gets pushed over. Make sure it’s placed somewhere out of reach and the cord is likewise secured so it can’t be pulled down.

Allergy, Asthma, and Respiratory Considerations

Adding moisture to the air can be beneficial for hydrating airways and reducing general irritation from dryness, but cool mist humidifiers are typically recommended if you have allergies or asthma. Evaporative models that have built-in filters are usually best, because the filtering process helps trap common allergens and mineral deposits and keeps them from being blown into the room. That means they don’t have the “white dust” issue common with ultrasonic models, which can be irritating if you’re already dealing with allergies or asthma. 

The self-regulating nature of evaporative cool mist humidifiers also prevents over-humidifying a room, another benefit for those with allergies or asthma since air that’s too damp can make symptoms worse.

Personal Comfort and Bedroom Environment Factors

Some people feel more comfortable in a cooler sleep space, so a cool mist humidifier is a natural fit. If you gravitate to something cozier, a warm mist model may be the better option. But don’t overlook room size. A warm mist humidifier works better in a smaller space because it works via passive evaporation, while a cool mist unit can handle bigger rooms and taller ceilings.

Tips for Choosing the Right Humidifier

The cool mist vs warm mist humidifier debate ultimately comes down to weighing their individual strengths and weaknesses. Here’s what to consider.

• Room size and humidifier capacity. It’s best to base humidifier size on the room in which you plan to use it. Smaller units are sufficient for smaller bedrooms, while large-capacity models are a better option for bigger rooms with taller ceilings. And again, cool mist humidifiers tend to work better than warm mist humidifiers in large rooms because they have a fan. It makes them more effective at pushing moisture farther.
• Safety features. Newer humidifiers are often equipped with safety features like automatic shut-off when the tank runs dry or is tipped over. Cool-touch exteriors, which are specific to warm mist models, are also a good idea, especially in a home with kids or pets.
• Ease of cleaning and filter replacement. It’s really important that humidifiers are regularly cleaned to prevent mildew buildup and impurities, which you don’t want to spread around in your home. A wide tank is easier to scrub, so that’s one consideration. If you’re using a model with filters, check that the replacements are easy to find and reasonably priced.
• Bonus features. Some humidifiers do more than just add moisture to the air. If you like the idea of incorporating aromatherapy, look for an integrated aroma diffuser. In a kid’s room, a model with a night light can be really handy. And if you’re tech savvy, humidifiers with smart features let you manage things remotely with an app. None of these features are essential, but they can be a convenient upgrade if you’re willing to spend the extra money.

The Takeaway on Cool Mist and Warm Mist Humidifiers

If your goal is adding moisture to dry indoor air, both cool mist and warm mist humidifiers get the job done. Deciding between the two is a matter of identifying what matters most in your home. Cool mist humidifiers add room-temperature moisture to the air and work better in large spaces. They work well in warmer climates or during the summer, and they can be a good choice year-round in milder climates. Plus, they’re safer in homes with kids or pets.

Warm mist humidifiers cozy things up in colder weather and are typically a quieter option. But they cover smaller areas, use more energy, and have a heating element that can be a safety concern with children or curious animals.

Factoring for your sleep environment, your health goals, and your personal preferences is the best way to decide between cool mist and warm mist humidifiers. Either way, you can add much-needed moisture to your bedroom, which may be exactly what you need for more restful nights.