Should I Put Hot or Cold Water in my Humidifier?

This article recommends whether you should put hot or cold water in your humidifier. 

Both hot and cold water have their benefits and drawbacks for use in a humidifier. 

Hot water is better for dealing with congestion and cough, whereas cold water in a humidifier is safer if you are using the humidifier around young children. 

Which one you use will depend on the type of humidifier you have, what kind of humidification you prefer, and any specific health conditions you’re trying to combat. 

We’ve tested both hot and cold water in humidifiers, and want to share our findings with you. 

Keep reading for more information about putting hot or cold water in humidifiers. 

Are Both Hot And Cold Water Safe To Use In A Humidifier

It is safe to use both hot and cold water in humidifiers. However, there are still some things to consider before you start putting on or the other in your humidifier unit. 

For example, if you have a boiling humidifier, it doesn’t make sense to put cold water in it, since it’s going to boil anyway. In fact, putting cold water in a boiling humidifier will only cause it to take longer to effectively humidify a space. 

Similarly, putting hot water in a humidifier can pose a serious burn risk, especially if there are young children nearby. Hot water also affects the longevity of your humidifier, as it can damage sensitive internal components unless they are specifically designed to be used with hot water. 

So what are the benefits of using hot or cold water in your humidifier? 

Benefits Of Hot Water In A Humidifier

One major benefit of using hot water in a humidifier is that hot water can achieve higher levels of moisture saturation. Since the water being used is hot, it produces mist that has higher energy particles that can cover larger areas more easily. 

Hot water also has some anti-microbial properties, killing a lot of germs and disease-causing bacteria in the air surrounding you. 

Hot water in a humidifier can be used with inhalants, creating a medicated mist that can be used to relieve symptoms of coughing, and cold. 

Similarly, a lot of people find hot water mist from a humidifier to be more soothing for dry throat and nasal passages, but that’s more of a personal preference. In fact, hot water mist might cause your nasal passages to swell, which can make it harder to breathe. 

And finally, hot water in a humidifier does have a slight heating effect on your surroundings, which makes for a cozy feeling. 

Benefits Of Cold Water In A Humidifier

Cold water humidifier mist is better if you want to improve your sleep quality. If you suffer from restless nights, running a cold mist humidifier might help you get a good night’s sleep. 

The same goes for excessive snoring. If you want to reduce snoring while you sleep, cool mist might be just the thing for you. 

Cool mist is also thought to be easier to breathe in than warm mist. That’s why a lot of people prefer to put cold water in their humidifier to counter congestion. 

Another major benefit of putting cold water in a humidifier is that it helps alleviate symptoms of allergies. The cool mist has a soothing effect on skin, and might even help calm down some flare-ups. 

Besides being great for your health, the cold water might also be beneficial for your humidifier unit. Cold water isn’t as damaging to the internals of a humidifier, which means you can get higher longevity out of the humidifier unit. 

Much like warm mist, cool mist doesn’t have the most noticeable effect on ambient temperature. Still, cool mist feels nice on your skin, even helping moisturize it faster. 

Using cold water is the safer choice, especially if you have young children. Cold water does not burn or irritate skin, the way very hot water does. 

So far, it seems like cold water is the better option of the two. But using cold water in a humidifier has some drawbacks of its own. 

The most common complaint people have is that cool mist humidifiers and humidifiers that use cold water are more susceptible to bacterial growth. 

This is because bacteria thrive in damp, cold places, so the water tank of a cold mist humidifier is at high risk. Still, regular cleaning and maintenance should prevent bacterial growth. 

And finally, there is a problem unique to cool mist humidifiers, not humidifiers that you put cold water in. Specifically, cool mist humidifiers tend to be louder than other types of humidifiers, which might be a problem if you are trying to sleep with the humidifier running in the background. 

What Type Of Water Should You Use In A Humidifier?

Now that we’ve looked at the benefits of using both hot and cold water, we must figure out what type of water to use in a humidifier. 

Distilled water is the best type of water to use in a humidifier. This is because distilled water is completely free of contaminants, and microbes, but also eliminates heavy metals, minerals, and other stuff that is still present in other types of water. 

The lack of any contaminants and microbes means the mist being released into your surroundings won’t harm you if you breathe it in. But the lack of any minerals or heavy metals reduces the chances of buildup in the water tank or filter of your humidifier. 

The chances of your humidifier developing mold are also significantly reduced by using distilled water. 

Purified water is another fine choice that is perfectly safe for use in a humidifier. However, it only filters out contaminants and microbes. 

It still contains a lot of minerals and some heavy metals. In extreme cases, these can cause problems in your humidifier, such as mineral build up and mold. These problems are quite improbable if you clean your humidifier regularly and change out the filter every now and again. 

We don’t recommend using tap water or bottled water in your humidifier. Both of these contain substances that can promote bacteria and fungus growth in the humidifier. 

‘Hard water’ i.e. water with a very high mineral content, is also not recommended for use in a humidifier as it can easily lead to development of mold. 

Does Boiling Water Purify It?

You might think it’s a good idea to boil tap water or hard water before using it in a humidifier. After all, boiling water purifies it right? 

Not quite. Boiling water does kill some types of bacteria in tap water or hard water,  but the vast majority of contaminants are still left in the water. 

Actual purified water undergoes lots of different processes in order to become as pure as it is. These processes include filtration, active carbon, and even treatments such as chlorination, flocculation, and ultraviolet light. 

This means boiling water will not suffice if you want to purify it. 

Does Boiling Water Turn It Into Distilled Water? 

This is a common misconception. Distilled water is produced by a process called ‘distillation’. DIstillation does involve boiling water, which is why so many people think boiling water distills it. 

But actual distilled water is made by boiling water, collecting the resulting steam, and then converting it to water. 

By doing so, distilled water eliminates not only all of the contaminants and microbes in the water, but also the minerals and heavy metals. 

The process of distillation does add to the cost of the water, and it means you will have to pay a bit more for it. However, the benefits of using distilled water in a humidifier are well worth it. 


So to sum up, both cold water and hot water can be used in a humidifier. Both have benefits of their own, and work better in different scenarios. 

Ultimately, which one you choose will depend on which of the benefits you value more. That said, both also have some unique drawbacks as well. 

Specifically, hot water isn’t the best for extending the longevity of your humidifier, as it can cause damage to the sensitive internal components. Hot water also poses a burn risk, especially if you use the humidifier in a child’s room. 

Cool mist humidifiers, on the other hand, are much more susceptible to bacteria and mold growth. But this is only really a problem with humidifiers that don’t get cleaned regularly. 

And regardless of the temperature of the water being used in your humidifier, you should use distilled water. Distilled water is better than other types of water as it is free of all contaminants, minerals, and heavy metals.

Purified water is a good alternative, and less expensive than distilled water. However, the presence of minerals means your humidifier will be more susceptible to build up and mold. 

Again, regular cleaning should prevent these problems, but it’s something to keep in mind.


Shawn Willis is all about humidifiers. After working for some of the biggest names in the industry, he started HumidifierGuys with Scott Dawson. Now, the dynamic duo helps others figure out what they need in their next humidifier.

Shawn is an avid sports fan, motorcycle enthusiast, and has two dogs named Whiskey and Boba.