How to Correctly Use a Dehumidifier to Eliminate Mold?

Josh Mitchell

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Josh Mitchell

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Holly Curell

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For years, I couldn’t understand how the mold in my home kept coming back so quickly.

That’s when I realized that cleaning wasn’t enough, I had to control the indoor environment too.

Dehumidifiers are one of the most powerful tools for managing your indoor environment, so I started to ask the question – can a dehumidifier remove mold?

Well, they can’t fully remove mold, but dehumidifiers can help with mold.

In this guide, I’ll explain how a dehumidifier could assist you in preventing and controlling the mold problem in your home and what you can do to help stop mold growth.

Key Takeaways

  • If mold has already contaminated your house, then a dehumidifier will NOT kill the existing mold. It will, however, slowdown the spread of new growth.
  • Mold thrives on high humidity as such dehumidifiers, by removing moisture content from the air, also prevent mold from thriving.
  • In order to get best results, it is recommended to manually wash off and remove all existing mold patches before turning on your dehumidifier.

Will A Dehumidifier Kill Mold In Your House?

Dehumidifiers will not kill mold already growing in your house.

However, dehumidifiers can slow the growth of existing mold patches and will prevent new growth by lowering the moisture levels in a humid environment.
will a dehumidifier kill mold

Dehumidifiers can also kill mold spores in the warm air, preventing them from spreading as far in your home.

How Does A Dehumidifier Help To Prevent Mold?

Mold and mildew growth is reliant on a high humidity level and dampness to grow which is why I always noticed mold in the dampest parts of my home.

However, a dehumidifier helps to remove that moisture and humidity – removing exactly what the mold needs the thrive.

Dehumidifiers work by pulling in damp air and releasing dry air, which is key for mold remediation because it stops mold from spreading.

Dehumidifiers also pull in contaminants like pet dander, dust, mold spores, and more.

This helps to improve indoor air quality and deal with the root of some mold problems.

They can also help to stop the musty smell that often accompanies mold and mildew growth.

As excess moisture is one of the biggest causes of mold growth, a dehumidifier is a useful ally in the fight against mold.

Dehumidifiers won’t remove mold, but they’re essential for mold prevention in damp areas.

TL;DR: A dehumidifier won't kill the existing mold. It will, however, prevent further mold from spreading or thriving.


Humidity is a double-edged sword. If the humidity falls too low, it can actually open a whole new can of worms for your health and belongings.

Maintaining optimal humidity is a fine balancing act. You must try to maintain it as close to 40% RH as possible.

5 Signs That You Could Have Mold In Your Home

1. You Are Facing Constant Sickness

A small amount of exposure to mold is normal, but long-term exposure to mold growth inside your home could worsen some health conditions, and cause some new ones, especially if you have immune-weakening conditions.

You may be allergic to mold and experience coughing, congestion, and watering eyes. Your skin could become flaky, itchy, and dry, or even break out in hives.

Mold can also impact people with asthma, which is why killing mold spores and taking mold remediation action is important.

2. The Walls Are Beginning to Bubble

If your painted walls begin to bubble, it’s a sign that the humidity levels are high and that mold may be present.

You should consider removing excess moisture and lowering the indoor humidity as soon as possible to prevent expensive damage.

3. There is a Musty Smell

Mold doesn’t just look unpleasant; it can also create a noticeable musty smell.

Keep a careful eye on any areas in your house that have poor ventilation or are exposed to moisture and high humidity levels on a regular basis.

4. Your House Has Water Damage

Moisture, excess humidity, and water leaks are some of the biggest causes of mold.

Should you have a leaky pipe or an easily flooded bathroom, watch out for mold.

Take extra care in the winter, as heat increases can also increase indoor condensation and humidity.

It’s worth remembering that for effective mold prevention and mold removal you’ll have to deal with the cause of the water damage first.

5. Excessive Rust Present In Your Home

Rust is often caused by high humidity levels and excess moisture, so if rust is present in your home, it’s quite possible there may be mold growth too.

Mold removal in these areas may also involve rust removal.

TL;DR: The effects of dehumidifier can manifest themselves both on your health as well as your belongings. Keep an eye out for the tell-tale signs of mold.

How Does Mold Develop In Your Home?

Mold is an organic fungal growth that spreads over decaying matter. It goes in places of high relative humidity and where there’s a lot of damp, humid air.

It’s common in basements, roofs, windows, and pipes, but can also grow on walls, wallpaper, insulation, and wood products.

I’ve even found it growing inside the brick chimney in my living room.

Mold spreads in areas of high humidity and moisture, which is why most mold remediation techniques involve using a dehumidifier (or another device) to improve indoor air quality and lower the relative humidity.

TL;DR: Mold has the highest chances of developing in areas that are often wet/damp such as basements and bathrooms.

Why Mold Is An Issue In The Home

Mold is all around us. In my home, I always noticed it in my bathroom around the seals, and on the walls of my basement and garage.

It enters our homes as airborne particles.

A small amount of these mold spores are harmless, but they may become a little more of a problem if they find a damp surface to grow on.

Damp homes with mold can be harmful to your health. They can cause respiratory problems, trigger allergies, and have an effect on your immune system [1].

Not only that, but mold can also cause damage to your belongings and if it spreads too far it can damage your home too.

The mold in my home made the whole room look dirty, but it wasn’t just the aesthetics that bothered me.

It’s important to prevent mold growth and remove mold wherever possible to keep you, and your home, in the best condition.

Dehumidifiers can be powerful tools to help you control mold levels in your home.

TL;DR: Mold can cause allergy and respiratory symptoms. It can also damage the home and your belongings.

Most Common Types Of Mold In The Home

It’s slightly scary, but it’s actually not known exactly how many types of mold are out there.

Some may not appear to cause any harm, but others could make your loved ones quite ill.

Molds that cause harm may be:

  • Allergenic – causing allergic reactions and asthma attacks
  • Pathogenic – which will impact anyone with acute illnesses
  • Toxigenic – producing harmful or toxic molecules that may cause significant harm

These are the most common types of mold that form in the home:

Alternaria - Allergenic Mold

This allergenic mold is very common. Surfaces infected by it may feel velvety to the touch.

It grows hairs that are dark green or brown, and may be present anywhere damp, such as in bathrooms or beneath sinks. It can also form around water damage.

This fast-growing fungus can impact health, with those exposed to it developing symptoms that mimic asthma.

Acremonium - Toxigenic Mold

This is a toxigenic mold, often found around humidifiers and air conditioning units.

If left untreated, its appearance will change from moist and small into a fine powder. It can come in a variety of colors, such as gray, orange, white, or pink.

This is one of the most dangerous types of mold, with the potential to cause bone marrow or immune system diseases, and could even damage brain function due to its carcinogen nature.

It can even team up with other kinds of mold and become even more dangerous.

Penicillium - Toxigenic Mold

This common mold is incredibly useful. Thanks to its production of penicillin, an important medicinal discovery was made.

It is also used to make cheese, but this probably shouldn’t be attempted with any you find growing on your wall! 

Penicillium can be found on spoiled food.

Aspergillus - Allergenic and Toxigenic Mold

This type of mold has over 185 species to its name. Its spores grow in thick layers in a flask shape in a wide variety of colors.

It is allergenic, and in certain conditions, it could present more of a toxic risk.

Exposure to it may cause asthma attacks, infections of the lung, and respiratory inflammation.

Black Mold - Toxigenic Mold

‘Black mold’ usually refers to Stachybotrys Chartarum. Some believe that this kind of mold can cause very serious health conditions such as mycotoxicosis.

However, it’s very rare to develop this from mold infestation, and this condition is normally caused by eating moldy food.

All types of mold are capable of producing toxins, but few do.

Although a study did find children brought up in a house with mold present may be more likely to develop asthma, Stachybotrys Chartarum was not one of the kinds most commonly linked with asthma.

TL;DR: There are many different types of mold. Some are allergenic, others are toxic. However, the one thing common for all is that they are all dangerous.

Which Type Of Dehumidifier Is Best For Mold?

Types of dehumidifiers

There are two main types of dehumidifiers; desiccant dehumidifiers and refrigerant dehumidifiers.

They both work to remove humidity from your indoor living space, and they will both work well at preventing mold.

I use a refrigerant dehumidifier in the most humid parts of my home where mold grows more readily (my basement and garage).

They are faster to act and remove moisture more quickly, stopping mold from spreading.

I prefer to use a desiccant dehumidifier in small rooms where there’s less moisture to manage (like my office).

It’s most important to get a dehumidifier that suits the job at hand. It needs to be:

  • Large enough to cover the area.
  • Have enough capacity to remove enough moisture from the air.
  • Be able to run for as long as you need it to.

Whatever your requirements, there will be a dehumidifier suitable for the job.

Both large and small units are available, so be sure to check your size requirements before you buy.

TL;DR: Refrigerant dehumidifiers are the most common type. Desiccant dehumidifiers are great for chilly winter conditions but are very expensive to operate.

how long to run dehumidifier

Portable Dehumidifiers Vs. Fixed Dehumidifiers For Mold

Both portable and fixed dehumidifiers will help to prevent mold in your home if you use them correctly.

The main difference is usually the drainage, as portable dehumidifiers will need to be emptied by hand whereas fixed dehumidifiers are usually plumbed in to drain automatically.

Portable dehumidifiers are best for those who only need dehumidification at certain times of the year, or in specific rooms of your home.

In my home, the humidity peaks in July/August time but dips in November/December.

I use several portable dehumidifiers in the dampest parts of my home during summer to prevent mold, and then store them away for the rest of the year.

If you have a big damp and mold problem then you should consider a fixed, whole-house ventilation dehumidifier.

These will remove moisture from your whole house and help to remove mold before it even forms.

TL;DR: Portable dehumidifiers are cheap and portable. Great for single room dehumidification. A whole-house dehumidifier is a fixed device that connects to your existing HVAC system and helps dehumidify your entire house.

Dehumidifiers Vs. Air Purifiers For Dealing With Mold

Air purifiers don’t remove moisture or reduce the humidity level in your home as a dehumidifier does, but air purifiers can remove dust mites and mold spores from the air.

This can stop mold from spreading around your home as it’s filtered through the air purifier.

An air purifier won’t remove mold, and won’t be as useful for mold remediation as a dehumidifier, but they can improve your indoor air quality and in doing so stop mold from spreading.

It may be worth looking for a dehumidifier with a built-in air purifier so you can reduce the relative humidity level, while also improving the air quality in your living space.

TL;DR: A dehumidifier improves air quality by removing moisture. It does not clean the air. To clean the air and improve the AQI, you need an air purifier.


If humidity levels in your home swing over the years with winters, for instance, getting excessively dry, you may even need a humidifier in your home.

5 Tips For Using A Dehumidifier To Help With Mold

1. Test The Humidity Level

Mold is able to grow generally in an environment that has between 50 – 65% humidity.

By using a hygrometer, you can test your home’s humidity level as a first step in tackling any mold.

If your humidity is over 50%, it may also be a good idea to have your home mold tested, either with an environmental contractor or via a home testing kit.

dehumidifier settings
In order to make your home inhospitable to mold, it’s ideal to bring the humidity down to 35% if possible.

I find that difficult to achieve in my basement so I aim for 45% instead.

Understanding your current relative humidity level will make it easier to choose a dehumidifier that meets your needs.

TL;DR: If humidity is consistently above 50%, chances are that you can have mold growth.

2. Clean The Existing Mold

To give your dehumidifier its best chance of helping your mold problem you should first clean any visible mold growth.

This can be done with bleach, vinegar, or cleaning products designed to kill mold.

If you are using stronger chemicals you should make sure the room is well-ventilated.

TL;DR: Clean all existing mold. A dehumidifier does not kill existing mold.

3. Choose The Right Dehumidifier (and the Size)

what size dehumidifier do you need

Be sure the dehumidifier you will be using is suitable for the space you will be using it in.

To help you remove mold you need the dehumidifier to be the right size to cover the space and have enough capacity to deal with the moisture levels and indoor humidity.

Set up your dehumidifier in your chosen room – bathrooms, basements, and kitchens are often prone to mold.

Different models will come with different modes – choose the model most applicable for the space it is used in.

Some settings even claim to help your laundry dry quicker!

TL;DR: You must match the dehumidification capacity of the dehumidifier with that of the coverage area.

4. Program Your Dehumidifier

Use the dehumidifier controls so it is reducing humidity to an appropriate moisture level.

Most dehumidifiers work by reducing the humidity to a certain % level, and you should try to keep it between 30-50% generally (in living areas I aim for 35%, and in my basement and garage I aim for 40-50%).

Keeping the humidity within these levels will help to alleviate allergy symptoms and stop mold from developing.

Turn on your dehumidifier, and enjoy the cleaner air supply and mold-free house.

TL;DR: Choose the most optimal settings for your dehumidifier depending upon the location you plan to use it in.

5. Clean & Maintain The Dehumidifier

Check how often you will need to empty the water collected in the tank, or if you will need to set up a hose for it to self-empty.

Find out how often your filters will need to be cleaned or replaced.

The better your unit is cared for, the better it will work and the longer it will last, and the better it will prevent mold from growing.

I open up and clean each part of my dehumidifier at least once every few months to keep it running properly.

If you use yours more frequently then you’ll need to clean it more frequently too.

TL;DR: Perform regular cleaning and maintenance of the dehumidifier. A dirty dehumidifier can actually become detrimental to your health.

People Also Ask (FAQs)

Will Mold Die If It Dries Out?

No, mold spores don’t die if they dry out, but they may become inactive. This still makes them a threat to health, but it should stop mold from spreading.

Can A Dehumidifier Spread Mold Spores?

Dehumidifiers can become a source of mold growth if they aren’t cleaned properly as they collect both mold spores and water.

Always clean your filters and your unit, and drain the water as soon as possible after the tank has filled.

What Can I Put In My Dehumidifier To Prevent Mold?

To stop mold from growing inside your dehumidifier, you should clean the unit regularly.

You can use a specialist cleaner, or a white vinegar solution mixed with water which works well. White vinegar can also be used to treat mold growth around your home.

What Humidity Level Kills Mold?

Humidity helps mold to thrive – to kill mold, reduce the humidity in your home to below 50%, or ideally down to 35%.

What Kills Black Mold Naturally?

The best natural remedy for black mold (or any type of mold) is white distilled vinegar.

Mix with water in a spray bottle, cover the mold growth and allow to sit for a while before washing away.

Dehumidifiers Can Prevent Mold from Thriving

Does a dehumidifier kill mold? Unfortunately not.

When I started using dehumidifiers in my home it didn’t magically remove the mold spots from the walls.

However, it did stop mold from coming back when I cleaned it off.

By reducing humidity and moisture levels in your home dehumidifiers can prevent mold from forming and stop it from spreading.

Hopefully, this guide has helped to explain how powerful a dehumidifier can be in the fight against mold, and you now know how to use your dehumidifier most effectively.


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Josh Mitchell


Josh Mitchell
My name is Josh and I am obsessed with home appliances. From portable AC units to heaters and air purifiers, I enjoy testing, learning and using these devices to improve the air quality inside my family home.

My Favorite Home Appliance?

Midea U Shaped Window Air Conditioner

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