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Cool Mist Or Warm Mist Humidifier?

For anyone buying a humidifier for the first time, it can be a little tricky trying to decide exactly which kind will be best for your needs. One of the main decisions you will need to look at is whether or not you want to buy a cool mist or warm mist humidifier. Generally speaking, warm mist humidifiers are a little on the cheaper side for a basic model, but each one kind has advantages and disadvantages. You can also buy combination warm and cool mist humidifiers, which gives you the best of both worlds. In this article we are going to talk about the differences between the two, and hopefully help you decide which one will suit your requirements.

Differences between cool and warm mist humidifiers?

The main differences between the two lie in how they create the humidity. Cool mist humidifiers come in two different varieties – evaporative and ultrasonic models. Evaporative models work by soaking a wick with water, then using a fan to blow against the wick. This forces the water out, and creates micro water droplets, which are then dispersed into the air. These are generally the cheapest humidifiers you can buy, although the fans often mean they are a little noisier.

Ultrasonic humidifiers work a little differently, as they use a diaphragm to vibrate at a very high frequency, which causes water to break up into mist. These kinds of models are often quieter as most are fan free, although some models do use very small fans to help the mist disperse quicker.

Warm mist humidifiers work differently, as these work almost like kettles. These models have a built in heating element, which heats up the water. The heated water vapour then naturally rises into the air, so no fans are needed in these kinds of models. However, the heating elements are much smaller than the ones you find in a kettle, and therefore draw less power.
This is the main difference between warm and cool mist humidifiers.

Which kind increases humidity faster?

Most people out there buy a humidifier simply to increase the humidity in the room, so the obvious question to ask is whether there is any difference between using cool or warm mist to increase the humidity. As far as we can tell, it makes no difference whether your use warm or cool mist to add humidity to the room – both work as well as the other. If you primary goal is to increase humidity, then the cheapest option may seem like the best option.

However, if cost is the main factor in your decision, make sure you keep reading on below to learn about some of the operating costs before making a purchase choice. There has been some discussion over the years about warm models increasing the room temperature slightly, which does make sense. So it is worth keeping this in mind, especially if you live in a warmer part of the country.

Now lets talk about some of the advantages and disadvantages of warm or cool mist humidifiers.

Warm mist humidifier advantage & disadvantages

Let’s talk about some of the advantages and disadvantages of warm mist models. As mentioned above, the basic models can be bought for as little as $15. Cool mist models generally start at around $25, so the warm mist models certainly seem to be more affordable. Since there are no fans involved with warm mist models, these models are all very quiet when in use, which is ideal for the light sleepers out there. Something else to consider is that since warm mist units don’t use filters, and they boil the water, there is less risk of mold developing inside and then being distributed into the air.

Filters for cool mist units can get quite pricey, so this does factor into quite a bit of savings in the long term. However, you can buy some filter free cool mist models. This also means the maintenance schedule for a warm mist model is not quite as rigid, but this is still something that you will need to do fairly often. And lastly you will find that you can use vapor pads in many warm mist models. These allow you to release scents into the air, which can help to deodorise the room or release vapors to help you breath a bit easier.

It sounds good so far, but there are one or two downsides to these kinds of models. Since these models are heating water all the time, the operating costs tend to be more than a cool mist model. In the initial few minutes after switching on, the heating element can draw up to around 800W of power, but this lowers considerably as the water heats up. They aren’t hugely expensive to run, but they do cost a little more than a cool mist unit. Another worry is if you have pets or children, as the hot steam released can burn or scald if the unit is accidentally knocked over, or even if they get very close to the output spout. Some of the Vicks models have a steam guard feature which aims to prevent scalds if a child or pet gets too close. Whilst this is an unlikely scenario, we felt it is worth a mention as this is an important aspect to consider.

Cool mist humidifier advantage & disadvantages

Now’s lets talk about some of the advantages and disadvantages of cool mist humidifiers. The first and main benefit of these kinds of models are the running cost. Generally evaporative models are very cheap, but they have the disadvantage of needing filters which increases the cost quite a bit in terms of long term usage. Ultrasonic models on the other hand cost a little more, but many of the models are filter free, which makes them the better pick between the two in our opinion. Ultrasonic models also have the advantage of being much quieter, so this is yet another reason not to opt for the cheaper evaporative models. There is also no need to worry about having kids or pets around these models, as the worst that could happen is they get a little wet in the event of an accident!

They do of course have a few downsides, which we need to mention. These models need to be cleaned frequently, to prevent any mold or bacterial growth. A cool mist humidifier will spit out whatever water is in there, no matter how long it has sat there. We recommend a weekly clean to keep them in good running order. And as mentioned above, if you buy a evaporative model, you do need to be prepared to buy filters and change these out every few weeks. So if you intend to buy a cool mist model, we would advise going for an ultrasonic one, as they are quieter and cheaper for long term use.
Below we are going to have a quick summary list of all the points we have talked about.


Warm Mist Pros & Cons


  • Cheap
  • Little chance of mold forming
  • Quiet
  • Can use vapor pads
  • Filter free


  • Cost more to run
  • Need to be careful around kids and pets

Cool Mist Pros & Cons


  • Cheaper to run
  • Ultrasonic models are fairly quiet
  • Many ultrasonic models are filter free
  • Child and pet friend


  • Cost a little more
  • Need to be cleaned often
  • Evaporative models can be a little noisy


That is a look at some of the main factors to consider when choosing between a cool mist or warm mist humidifier. You will need to have a look at the pros and cons of each one, to see which will be best for your needs. If you want the best of both worlds, you could always opt for something like the Boneco 7147 model which we looked at over here.

Alternatively feel free to have a look at our entire humidifiers section to get an idea of which models are worth your money.

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