Cool Mist vs Warm Mist Humidifier

Cool Mist vs Warm Mist Humidifier

When purchasing a humidifier, the first decision most homeowners have to make is choosing between a cool or warm mist system. Each brings unique benefits to the table, and while both will moisturize the air, there’s a big difference in how they work. In our cool mist vs. warm mist humidifier guide, we’re going to compare these two systems while touching on the pros and cons of each model.

Cool Mist Humidifiers

A cool mist humidifier is a simple system that disperses room temperature moisture into the air of your home. There are two types of cool mist humidifiers to consider as well with evaporative and ultrasonic systems.

An evaporative humidifier has a wick filter that draws moisture from a water reservoir. An internal fan blows across the filter, which releases moisture and sends it throughout your home. It is the most common style of humidifier sold today, although ultrasonic systems have become incredibly popular as well.

Ultrasonic humidifiers can look identical but have a nebulizer in place of a wick. These machines vibrate at extremely high frequencies to turn water into vapor. An ultrasonic humidifier still has a small fan, but it’s quieter and creates a finer mist.

Cool Mist Humidifier Pros

  • Energy-efficient
  • The safest option for homes with children or pets

Cool Mist Humidifier Cons

  • Not ideal for winter use
  • Fans on some models are noisy
  • A chance for bacteria buildup

Warm Mist Humidifiers

As the name implies, a warm mist humidifier emits warm mist. They accomplish this through boiling water inside the system, which then releases steam. There are no internal fans on these humidifiers, and they can warm up the air in a chilly room in a matter of minutes. When you want to use essential oils or medicated inhalants, a warm mist humidifier is often the best alternative.

Warm Mist Humidifier Pros

  • The quietest type of humidifier
  • Perfect for winter and colder climates
  • Reduces the possibility of bacteria

Warm Mist Humidifier Cons

  • Not ideal for children’s rooms or homes with pets
  • Uses more energy


Coverage is a specification that tells you how large of a room a humidifier is suitable for. It’s measured in square footage, although a number of companies use traditional tags like small, medium, and large rooms as well. When comparing coverage with a cool mist vs. warm mist humidifier, one system is a clear winner.

Unless you opt for a whole house steam humidifier, there are more sizes at your disposal with cool mist humidifiers. Coverage for these machines can range anywhere from 150 square feet to over 6,000 square feet depending on the type of system and what your budget can accommodate. They are designed to deal with larger areas, while steam humidifiers are better suited for smaller rooms.


Whenever you hear the term capacity with humidifiers, it refers to how much water a humidifier can hold. This is another area where steam humidifiers take a hit as it’s not uncommon to find cool mist humidifiers anywhere from 1 to 6 gallons in size.

You can find large steam humidifiers as well, but there aren’t as many options, so you’re limited when it comes to brands and features. Both systems have a variety of units under 1-gallon that are portable, but steam-based machines tend to top out around 2 gallons.

Runtime is another factor to consider with capacity. The larger the tank, the longer a humidifier can run… in most cases. The type of humidifier can affect the output rate, but high-efficiency humidifiers can run longer than systems with tanks twice the size.  


Keeping your humidifier clean is important, regardless of whether it’s a cool or warm mist system. While some machines are much easier to clean than others because of the design, there is one key difference. Water in a cool mist humidifier is more prone to bacteria, whereas a warm mist humidifier can eliminate 99% of contaminants before they reach the air.

Boiling water helps keep the humidifier sanitary, although companies also use antimicrobial technology in their tanks to help as well. Mineral buildup can occur in both systems, so performing routine maintenance is key with either type of humidifier. We feel these systems are tied when it comes to maintenance, as it largely depends on the design of the humidifier and the quality of the water used.


Cool mist humidifiers are safer than warm mist humidifiers simply because they don’t heat the water. There’s no chance you could be burned if the machine tips over, which makes them a great choice for homes with pets or children. A warm mist humidifier can be perfectly safe, but there’s still room for human error.

That can result in burns from the hot water inside the machine, which makes cool mist humidifiers safer all-around. There are also several built-in safety features with both styles, including automatic shutoff for tip-overs or empty tanks, and control locks.


You’ll find a similar set of features whether you choose a warm mist or cool mist humidifier. We’ve seen both types of systems come with features like digital humidistats, multiple modes, and timers. You can also find a handful of humidifiers with remote controls, and dimming features are fairly common along with nightlights.

While it’s no substitute for a vaporizer or warm mist humidifier that works with essential oils, you can find cool mist humidifiers with vapor trays. These allow you to take advantage of the benefits of aromatherapy, while still experiencing a cool, soothing mist. There are also humidifiers that can disperse warm or cool mist if you’re willing to pay a premium and aren’t concerned about hot water.


This is another area where the brands of a humidifier and its features greatly affect the price. You can find comparable systems in both styles, but overall we feel that warm mist humidifiers are priced at a slight premium. The price difference becomes more noticeable with larger humidifiers, so you can find small affordable systems under 1-gallon in either style.

The Verdict

There are plenty of similarities between warm and cool mist humidifiers, and both are great for dry skin or sinus issues. With that in mind, a cool mist dehumidifier is a better choice for warm weather, children’s rooms, or large areas. They are cheaper to operate continuously, and you don’t have to worry about scalding hot water.

When bacteria is a concern, or you want a nearly silent system in the winter months, a warm mist humidifier is often the better choice. If you still can’t decide which is best suited to your needs, our humidifier guide will help you better understand the differences between every type of humidifier currently available.

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree from Lone Star College and EPA & R-410A Certifications.

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