Can You Use a Diffuser as a Humidifier?

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Image of steam coming from vaporizer and text overlay of can you use a humidifier as a diffuser and vice versa?

When the humidity in your home takes a tumble and your skin, eyes, and sinuses are feeling dry you may seek relief. I know I do.

I hate having multiple appliances for similar uses, but really found myself wondering if I should invest in a humidifier. After all, ultrasonic diffusers use similar cool mist technology as humidifiers do, and I already had several. After a little research and I ended up with two questions:

  1. Can I use essential oils in a humidifier?
  2. Can my ultrasonic diffuser double as a humidifier?

What is a humidifier?

A humidifier is an appliance that adds moisture to the air. This can be useful in dry climates, and even in wet climates during winter when furnaces are running throughout the day.

There are several varieties of humidifiers, but ultrasonic humidifiers come closest to ultrasonic diffusers. These appliances both have a water reservoir and use ultrasonic waves to break up water into a fine mist.

Humidifiers come in both warm and cool mist types.

What is an ultrasonic diffuser?

There are also many types of diffusers, but for the purposes of comparison we will focus on the ultrasonic diffuser.

The ultrasonic diffuser is designed to break up a mixture of essential oils and water into a fine mist. Diffusers almost always emit a cool mist.

This table summarizes the similarities and differences:

Table comparing the similarities and differences between diffusers and humidifiers


As you can see, they have a lot in common. The big difference is in the purpose. Humidifiers are designed to moisturize the air. As a result, their mist output is generally greater than a diffuser.

A diffuser’s main purpose is to create a fine mist of essential oils. The water is a carrier for the essential oils and moisturizing the air is a side effect of creating the mist. As a result, diffusers may not put enough moisture in the air to significantly alter the humidity.

The other main difference is in construction. Humidifiers are designed to work with water. The plastic reservoirs in humidifiers are made to hold water.

Essential oils are not kind to plastics and there are many reports of people’s humidifiers being ruined from cracked and leaking reservoirs after they used essential oils in them.

Diffusers also have plastic reservoirs, but it is a type of plastic that will withstand having essential oils in them.

What other considerations are there?

Essential oil diffusion is recommended as needed in short intervals. A diffuser should be run for up to 30 minutes at a time, a few times a day.

We have already discussed that a diffuser will output less mist than a humidifier, so when we can only run it a few hours a day, it may not make a lot of difference to the humidity.

Of course, this is assuming you are using essential oils in your ultrasonic. If you are running it with plain water, then you can run it as long as you want.

Will a diffuser raise the humidity in a room?

I decided to run an informal test to see if a diffuser can really raise the humidity in a room. I used a cool mist humidifier and compared it to the Innogear ultrasonic diffuser.

On one day, I ran the humidifier for 30 minutes in a bedroom. I used my son’s weather station to measure the indoor humidity.  It started at 22% and at the end of 30 minutes, measured 26%.

On a different day (so that the humidity could return to normal) I ran the diffuser with plain water for 30 minutes in the same position and in the same bedroom. The starting humidity was 23% and after 30 minutes, the humidity was 24%.

So, the humidifer definitely had a bigger impact on humidity, raising it 4% while the ultrasonic caused a slight impact on humidity, raising it 1%.

Summary & Recommendation:

So, to answer our questions. Can you use essential oils in a humidifier? You can but I don’t recommend it as the reservoir may not be designed to withstand essential oils. You may void your warranty and potentially ruin your humidifier. Do so at your own risk. If you do decide to try this, remember that essential oils should only be diffused for a limited amount of time.

Can you use an ultrasonic diffuser as a humidifier? You can, but it may not have enough of a mist to make a difference in your humidity level and you should only run a diffuser with essential oils for short periods of time.  You could however, run your ultrasonic with plain water for as long as you wish.

I recommend that if you only need a little bit of humidity added to your room air, you can use your diffuser. If you need to add more humidity, then choose a humidifier and get a separate diffuser for essential oils.


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