How Long Until a Humidifier Starts Increasing Humidity?

Ile Kauppila

Written By

Ile Kauppila

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Josh Mitchell

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You’ve turned your humidifier on, but it doesn’t seem to have any effect. I can understand that you might get impatient, especially if you’re using the unit to treat cough or asthma.

Humidifiers aren’t instantaneous miracle machines. They can take up to a day to humidify the air, depending on various conditions.

But what are those conditions?

Read on and I will tell you everything you need to know about how long your humidifier will take to work!

Key Takeaways

  • Humidifiers can take between a few hours to 24 hours to humidify your living space.
  • The speed at which a humidifier raises moisture levels depends upon what type it is, its initial ambient humidity level, the size of the living space, and its mist-producing capacity.
  • Choose a humidifier with a mist output that matches the square footage of the room.

How Long Does It Take For A Humidifier To Work?

A humidifier can take anywhere from one hour to an entire day to increase the humidity levels in your home.
how long do humidifiers take to work

I wish I could give you a more accurate answer, but it’s simply not possible.

A whole slew of factors affect the time it takes for a humidifier to work (I’ll get to these a bit later).

As such, I can’t tell you exactly how long your humidifier will need to take effect.

What I can do is tell you some basic guidelines!

Once you turn them on, most humidifiers don’t take long to start producing water vapor.

Some units, like ultrasonic humidifiers, start working nearly instantly, while warm mist units might need up to 15 minutes to warm up.

After it’s started working, you should start feeling the humidity rise within three hours.

Important Tip:

Don’t panic if you do not feel humidity rise in a few hours, though — especially if the device is brand new.

It may take your unit up to 24 hours to raise the relative humidity in your home.

If you don’t notice a difference by the next day, I say it’s time to start troubleshooting.

Once you do notice the humidity levels are rising, keep an eye on them.

What are the Optimal Humidity Levels

The ideal humidity level for indoor air is between 30%-50%. I recommend investing in a cheap humidity meter so the air in your home doesn’t get too damp.

TL;DR: Humidifiers do not raise the humidity levels immediately. They can take anywhere between a few hours to an entire day to humidity the air.

How Long Do Different Humidifiers Take To Work?

The humidifier’s type is quite possibly the most important factor in how long it will take to humidify your home.

Types of humidifiers

Each humidifier model works differently and some of them are faster than others.

I’ve broken down the average times each type of humidifier takes to work below.

Warm Mist Humidifiers

A warm mist humidifier can take quite a while to humidify your living space, especially in a large room.

To begin with, these units rely on boiling water to create warm steam, so it will take around 15 minutes for the machine to boil the water in the humidifier tank.

Warm mist humidifiers can take up to 24 hours to humidify a large room. Because they’re relatively slow, I recommend using them in smaller spaces.

Ultrasonic Humidifiers

I love ultrasonic humidifiers because they’re very efficient.

They begin humidifying the air almost instantly after being turned on.

This is because they use an intensely vibrating plate to break water into tiny water droplets that evaporate quickly into the air.

An ultrasonic humidifier should humidify the room in a few hours.

Impeller Humidifiers

An impeller humidifier is a cool mist humidifier that works much like an ultrasonic one.

The difference is that they use rotating discs to produce a cool mist.

As such, they take about the same time to work as ultrasonic units.

Some impeller units can dispense cool mist in a 360° range around them, so they may be even faster.

Evaporative Humidifiers

An evaporative humidifier will take a little while to start working because it operates by absorbing moisture into a wicking filter and blowing air over it to create water vapor. It can take the unit 10-15 minutes to soak the filter.

Important Note:

The wick filter on evaporative humidifiers needs to changed every 1-4 months depending upon what make and model it is.

Evaporative cool mist humidifiers are very efficient once they kick in, though.

Even a larger room should begin to see higher humidity levels within a few hours.

Whole-House Humidifiers

Whole-house humidifiers — also called furnace humidifiers — are installed into your home’s HVAC system to add moisture to the entire house.

how does a whole house humidifier work

They often take the longest to work since they have such a huge area to humidify.

A whole-house humidifier can take up to a couple of days to reach the desired humidity level.

On the plus side, they’re practically always connected to a humidistat, so you can just turn them on and let the machine take its time without worrying about whether the humidity rises too high.

TL;DR: Depending upon the type of humidifier you have, the speed at which the moisture content in the air rises would defer.

Why Is My Humidifier Taking Longer To Work?

One of the most common questions people ask me is why their humidifier is taking so long to work.

There are a few common reasons that might make your unit work slower than it theoretically should.

Very Dry Air (Low Initial Humidity Levels)

A cold and dry climate is one of the most prevalent causes of slow humidifiers. It makes sense, really.

If you live in an area with very low humidity, your humidifier will need more time to add moisture to the air.

Hot Ambient Temperature

Very high outdoor temperatures (like those in my home region) can make some of the moisture your humidifier produces dissipate very quickly.

As such, it takes a longer time for the humidity to build up in your home.

Unit Not Placed In The Correct Location

A poorly chosen location can seriously hinder a humidifier’s effectiveness.

Living room humidifier placement

I will get back to this a bit later, but generally, you should put your humidifier in a central location with plenty of space around it.

Dirty Or A Clogged Humidifier

A dirty humidifier can get clogged with mineral deposits, mold, bacteria, or rust that hinder its mist output.

You’d be surprised how often I see people’s humidifiers start working much faster after I suggest they clean the unit properly.

TL;DR: There are many reasons for humidifier taking long to work, some in your control like the placement, others not in your control, like the initial humidity levels.

Can You Speed Up A Humidifier?

You can’t make a humidifier work faster than its maximum setting allows, but you can do a few things to help your unit.

Here are some tips that I’ve found effective.

First of all, you should place the humidifier in the center of the room on an elevated platform, like a desk.

Doing so ensures moisture disperses in the air instead of condensing on walls or furniture.

If you’re trying to humidify a single room, you can close the doors and windows to prevent the water vapor from wafting elsewhere.

All the moisture stays in the room, while you also keep drier outside air from getting in.

You can also set up fans next to the humidifier.

The fans will boost the airflow and distribute moisture throughout the entire space, raising humidity levels more evenly.

I’ve found this trick works best with smaller humidifiers that tend to release moisture in a concentrated area.

Important Note:

Avoid over humidification as humidity beyond 60% can be determinantal to both your health and belongings.

Finally, you could buy some houseplants! Plants increase ambient humidity by “sweating” through a process called evapotranspiration.

My houseplants help my humidifier work better, and the unit also keeps my plants healthier — a win-win. (1)

TL;DR: From plants to wet towels and using a fan, there are many tricks to raising the humidity levels quickly.

Factors That Affect How Quickly A Humidifier Works

A lot of things in your home can help a humidifier work faster — or slow it down to a crawl.

Here’s my breakdown of the most significant things about your home environment that can affect your humidifier’s efficiency.

Size Of The Room (Coverage Area)

A larger room has more air in it, so it naturally takes a humidifier a longer time to humidify a big space.

humidifier sqft coverage
This is why you should match the humidifier’s output to the square footage of the room you want to humidity.

Don’t judge a humidifier by its physical size — a big unit still may not have what it takes to work in an enormous living room.

Low Ambient Humidity Means Slow Humidification

A humidifier may work quicker if your home has fairly humid air, to begin with.

Household tasks like cooking or showering raise humidity levels momentarily, which can the job easier for a humidifier.

If your home already has moist air, though, keep a sharp eye on a hygrometer to make sure you don’t add too much humidity to the space.

Room Layout – Irregular Room Is Difficult To Humidify

Open spaces make a humidifier work faster, as the moisture gets distributed throughout the room more evenly.

Rooms with long narrow sections or recessed areas can hinder your humidifier’s effectiveness.

Humidifier Placement

As I already mentioned, a raised central location allows your humidifier to work faster.

If you tuck the unit in a corner, it will take longer to work and you might damage your walls with moisture and mold.

Humidifier placement in bedroom

In general, I recommend keeping a humidifier at least three feet away from all walls and furniture.

Important Tip:

Consider purchasing humidifier with an upward/vertical direction of mist stream to disperse the vapor evenly. 

Humidifier Capacity – How Much Mist Can It Actually Produce

How much mist a humidifier puts out will affect how quickly it can work in your living space.

A small humidifier will work fine for tiny rooms, but it will take a long time to be effective in large areas.

On the other hand, if you buy a humidifier that is too big for your space, you increase the risk of creating an environment that is too moist.

Furniture And Textiles Absorb Humidity

Moisture-absorbing surfaces — like wooden furniture and textiles — will slow down a humidifier.

These materials naturally suck up some of the vapor your humidifier emits and draw it out of the air.

On a positive note, though, a humidifier can help your wooden furniture last longer by preventing drying and cracking!

TL;DR: The primary factors that affect how long it takes to humidify are the size of the room and the humidification capacity of the humidifier.


Can You Humidify A Room Too Much?

Yes, you can humidify a room too much. Excessive humidity can create a favorable environment for mold and dust mites, and it may aggravate allergies and asthma.

How do I know if my humidifier is working properly?

You know your humidifier is working properly when you notice a decrease in static electricity and dry skin. I also recommend buying a hygrometer so you can monitor the relative humidity level in real-time.

Should The Humidifier Run All Night?

It’s generally safe to run your humidifier all night. However, you must make sure the unit won’t run dry or increase the humidity too much overnight.

When Is The Best Time Of Day To Run A Humidifier?

The best time of day to run the humidifier is right before you go to bed. Higher humidity can help you sleep better, keep your airway moist overnight, and reduce snoring.

In Short, A Humidifier Takes Its Time

I know it can be frustrating to wait for your humidifier to improve the air quality in your home.

You have to remember, though — good things come to those who wait.

You now know what factors can increase or decrease the effectiveness of your specific humidifier.

Follow the tips I’ve given and you’ll be breathing in well-humidified air in no time!


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Ile Kauppila

MA Multimedia Journalism / BA English Philology

Ile Kauppila
Ile Kauppila is a globetrotting writer and editor living in Virginia. Ile holds an MA degree in Multimedia Journalism and a BA in English Philology. Ile has written for a variety of home, HVAC, and energy-related websites and publications. He has covered HVAC solutions, insulation, and energy-efficient construction, automotive AC systems for multiple auto dealerships and garages.

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