Can A Dehumidifier Prevent Mold?

Mold can accumulate and thrive in places that are in constant and prolonged contact with moisture.

This problem can commonly occur during spring when there is groundwater runoff and in colder months in the form of condensation on windows, but it can also happen due to a flawed ventilation system, powerful humidifier, or damaged plumbing.

The best remedy to a mold problem can often be through the use of a dehumidifier.

A dehumidifier helps to eliminate excess moisture from a room, which in return can help mold from appearing by preventing it from growing in the first place. The use of a dehumidifier can also help prevent a mold problem from getting worse.

We found that condensation and resulting mold started to become more of a problem since spending more time at home and so this is one of the main reasons we bought our current desiccant dehumidifier.

Window Mold
Mold that started accumulating around our windows before we bought our dehumidifier

You’ll need to know the humidity level you should maintain in the house to prevent mold from growing and whether dehumidifiers can kill mold, which we discuss and explain through this article.

How Effective Is A Dehumidifier In Preventing Mold?

Mold thrives on wet environments such as leaky pipes, sinks, roofs, or windows.

An increase in moisture, commonly during spring, results in a mold overgrowth, especially in rooms with poor ventilation.

Mold can also grow in the neglected parts of the room, such as dark corners and under the furniture. If left unchecked, a mold infestation can grow out of control and spread around the house.

A humidifier could also be responsible for mold infestation, especially if you overuse it.

A dehumidifier helps to prevent this problem by eliminating excess moisture from the room.

For a dehumidifier to work, you still need to know how much moisture there is in a room. This can be done using a hygrometer; often built into dehumidifiers.

A dehumidifier works by eliminating excess moisture from the air, which in return helps to prevent mold from growing.

Our own dehumidifier has made a massive difference to our home in terms of mold growth.

As it’s a portable model we can move it around the home as we see fit and help to prevent condensation forming on the windows, which in our case was causing the mold to start.

Our dehumidifier

However, it has little effect on the existing mold.

Mold can remain dormant for a very long time; that’s why using a dehumidifier can only help to prevent it.

Window Mold
Using a dehumidifier could have helped prevent this mold

We therefore had to remove this existing mold using other means as our dehumidifier wasn’t able to help, which we discuss later in this article.

How Long Does A Dehumidifier Take To Clear Moisture From The Room?

On average, a small dehumidifier takes around 12 hours if it’s new to lower moisture in a room to sufficient levels.

It also depends on the dehumidifier model you have since powerful ones are known to take around 20 minutes to clear moisture from the room. However, you still need to consider certain things to estimate how long a dehumidifier will take to work, such as:

  • The size of the dehumidifier – Small ones take longer.
  • The size of the room – Larger rooms will require more time to get rid of the excess moisture.
  • The amount of moisture in a room – If the room is flooded with water or foggy with steam, it’ll take longer to clear out.

What Is The Best Humidity Level To Prevent Mold?

On average, you should do your best to keep indoor relative humidity (RH) between 30% and 50% of any room temperature if you want to prevent mold from growing.

To help prevent mold from growing, ensure that humidity in a room doesn’t exceed 60%.

You should also maintain the temperature at a maximum of 30 degrees Celsius (860F) within your house.

The best way to get accurate figures is to get a thermometer or a hygrometer, which helps identify when the temperatures go up or when there is too much humidity. Even so, certain precautionary steps, such as opening windows or buying an indoor fan, will help regulate room temperatures, ensuring moisture doesn’t accumulate in the house, which attracts mold.

Cleaning the house more often, especially behind the furniture and other substantial household items, will help to reduce humidity in the house. Make sure you dehumidify the laundry room to prevent any moisture from building up in this part of the house. Dry the clothes well before taking them to the house.

Dehumidifier Drying Washing
A dehumidifier is almost essential for preventing mold when we dry our clothes our in the house

Not only has cooking been known to increase room temperature, but it also affects humidity since moisture and water vapor escapes from the food and into the air, hence making your house a hot spot for mold growth. Make sure you invest in a proper HVAC system that directs this moisture outside.

Which Parts Of The House Are Affected By Mold?

As a whole, mold can grow in any place, provided it is wet and moist enough to provide the necessary nutrients.

However, there are common areas where mold infestation should be expected. It is good to know where these places are, so you can have your dehumidifier ready to do its job where practical.

  • Bathroom roofs and walls – Bathrooms are vulnerable due to the steam. Bathrooms with poor ventilation to push the moisture out are likely to be more affected than those with proper ventilation.
  • Basements – Nearly every house with a basement experiences unsuitable living conditions, and one of them is mold. This is caused by groundwater runoff, flooding, busted pipes, and poor ventilation.
  • Under the sinks and leaking pipes – It’s usually a guarantee to find mold growing under the sink and near leaking pipes since these areas provide darkness and moisture in abundance for mold to thrive.
  • Crawl spaces with bare earth floor – Soil holds moisture, which it releases more often into the air. Crawl spaces are perfect for mold infestations since not much cleaning takes place in these areas.

Can A Dehumidifier Kill Mold?

As a general rule, a dehumidifier works by taking moisture out of the air to prevent damp and wet conditions, which helps to prevent mold from growing.

However, a dehumidifier does not affect already-grown mold and cannot kill it.

It’s also important to know that mold can remain dormant on the walls and in the air for a long time and will only start growing if the right conditions are met.

Dehumidifier Plugged In
A dehumidifier wont be able to remove mold once it’s grown

Even so, there are some methods you can use to get rid of mold on your wall. They include:

Using Paint Killer

One of the easiest ways of killing mold is painting over it with Zinsser Mold Killing Paint.

The paint acts as a fungicide and has been approved by EPA for this purpose. It will kill all types of molds and fungus. The paint is water-based and works almost immediately. It’s perfect for homes with extreme mold infestation.

Using Vinegar Solution Or Bleach

The natural way of killing mold in your home is by using vinegar solution or bleach.

However, the vinegar used in the kitchen might not be as effective as it contains only 1% of the acidity required to get the job done. Instead, opt for the industrial vinegar with 20% acidity.

On the other hand, bleach works perfectly and can be used to clean and kill mold right from the bottle. However, you still need to dilute it a bit to avoid damaging any fabrics that might be around the scene.

Vinegar and bleach solutions should only be used on small scales, such as killing mold on furniture or small parts of the wall. In the case of furniture, make sure the furniture’s fabric is not affected by vinegar or bleach before using them.

Ammonia and hydrogen peroxide are other natural ways to kill mold. However, there are concerns regarding their usage, with the former having a pungent odor and the latter frowned upon due to its toxicity.  


Mold can be an embarrassing issue to have in your home. High humidity and wetness are the primary causes of mold taking root.

A dehumidifier can prevent mold from growing since it helps to remove excess moisture from the air.

A dehumidifier cannot kill mold, but mold-killing paint can get the job done. Using natural methods such as vinegar and bleach can also help to kill off the mold.

Further Reading

Does A Dehumidifier Need To Be On All The Time?

Does A Dehumidifier Have Or Need Filters?

Can A Dehumidifier Also Be A Humidifier?

Can A Dehumidifier Act As An Air Purifier?