Dehumidifier Mold Exposure

Mold growth inside of a dehumidifier tank

When performing indoor environmental investigations for clients, I like to teach them how to avoid dehumidifier mold exposure. Would you like to learn how? If so, this article is for you.

Dehumidifier being used in basement

People purchase dehumidifiers to reduce the humidity in their homes. They often purchase dehumidifiers for basements where high humidity is most common. The hopeful outcome is to protect indoor air quality and prevent mold growth in their home and on personal property.

When not used properly, as I discover in 8 out of 10 homes, dehumidifiers can be the cause of mold growth, and can actually spread mold spores throughout homes.

It’s too late

Unfortunately, many people put off purchasing a dehumidifier until AFTER they experienced water damage, a flooded basement, or have spent money on basement waterproofing.

Even more common, people purchase dehumidifiers after they’ve had high humidity for an extended length of time. At this point, there’s about a 100 percent chance hidden mold contamination already exists in their homes.

In some instances, people already know they have a mold problem. They’ve either seen some black mold or mildew or could detect a musty smell in the air. They dehumidify and often use air filters and air purifiers to try and trap mold spores. It’s too late. At this point, dehumidifying only temporarily stops the musty smell (digestive gasses) and active growth of mold because the mold simply goes dormant. It does not die or disappear.

Dry mold goes to sleep

Just like trees lose their leaves in the fall and go to sleep for the winter, mold goes to sleep when humidity leaves the air. When this happens, many molds release significant amounts of mold spores into the air as humidity levels drop. Mold releases spores that float through the air and spread to new locations. It’s a survival mechanism.

Using a dehumidifier, after mold growth occurs, is misleading. Dry mold will be present. Whenever the day comes that sufficient humidity returns, any pre-existing mold simply wakes up and starts growing and spreading again.

Remaining dry mold can still cause both allergy symptoms and asthma symptoms. Additionally, molds that are toxigenic can cause headaches, migraines, memory loss, ADD, and ADHD.

Moreover, pathogenic (infectious) mold spores that remain after dehumidification will continue to cause sinus infection, ear infection, and lung infection. Some doctors also believe infectious molds are a cause for many types of cancer.

For all these reasons, I thought it would be a good idea to write this article for you and others who may be researching dehumidifier reviews or looking for instructions on how to use a dehumidifier. I hope you benefit from it and share it.

 5 causes of dehumidifier mold exposure

There are many contributing factors to subtle, yet unsafe humidity levels indoors. Therefore, I encourage you to learn all you can about moisture sources and humidity control. All the vital information on these and other indoor air quality topics can be found in the store.

Indoor environments are relatively consistent no matter what climate you live in. This means that homes in any climatic region have the possibility of growing black mold, white mold, and species of other colors inside their homes that can result in mold symptoms.


The amount of mold growing in homes due to roof leaks, plumbing problems, and flooding, pales in comparison to the amount of mold growing in homes due to slightly high indoor humidity.

Now let me show you the five ways dehumidifier mold exposure makes people and pets sick.

 1) Are you guessing your humidity level?

Unfortunately, people only think to use their dehumidifier when it feels humid in their home or basement. Don’t guess – use a humidity gauge. Human perception should never govern dehumidifier settings. I have two gauges in my home and I keep my eyes on them all year long.

Dehumidifier with built in humidity gauge     Portable free standing humidity gauge

Some dehumidifiers have humidity gauges built into them. This helps in the vicinity of the dehumidifier, but if dehumidifiers for basements or crawl spaces are not in immediate view, then you should have a free-standing gauge in the primary area of your home to monitor indoor humidity.

  • Indoor humidity should not be lower than 25 percent RH or you’ll get shocks or nosebleeds.
  • Maintain indoor humidity lower than 50 percent RH to prevent mold growth.
  • An occasional spike above 50 percent typically won’t present a problem.
  • Monitor indoor humidity all year long to know exactly when dehumidification is necessary.

2) Are you turning your dehumidifier on?

This seems obvious, but let me explain. Far too often, I find dehumidifiers in mold-contaminated homes and basements sitting unplugged. Some people unplug them because they’re noisy. Others unplug them when conditions are dry, but then forget to plug them back in when needed.

Dehumidifier left in the box and the box grows mold on it

One of my clients purchased a brand new dehumidifier and left it in its unopened box. Personal property items throughout her home, including the box the dehumidifier came in, became severely contaminated with mold growth. She learned her lesson the hard way.

3) Are you cleaning your air filter?

I can’t tell you how many times my clients did not know their dehumidifier even had an air filter.

Dehumidifier dust screen filter hidden inside and plugged up

A dirty filter stops air flow through the dehumidifier allowing detrimental humidity to increase. Clogged air filters can also cause expensive mechanical damage to dehumidifier compressors.

  • Know where your filter is located
  • Check the filter every 30 days
  • The filters can be rinsed under a faucet or vacuumed clean.

4) Is there mold growing inside the water collection tank?

Black mold growth can hide inside of water collection tanks on dehumidifiers. Obviously, it is wet inside these tanks, so all it takes is some dust particles and one mold spore to start a contamination problem.

Mold growing inside of a dehumidifier water collection tank

As shown below, water that sits stagnant inside of collection tanks can also grow toxic bacteria that can make people extremely sick.

Toxic bacteria growing inside of a dehumidifier water collection tank

I had a client that was bedridden and her medical doctor recommended she contact me to have her home inspected for mold. What I discovered was that she was being poisoned by toxic bacteria growing inside of the dehumidifier tank. After I sanitized the water tank and ventilated the bacterial gas out of the house, she reported having a full recovery in a matter of days.

To prevent black mold or bacteria from growing in the water collection tank, I recommend entirely bypassing the water collection tank. You’re much better off using a hose connected directly to the dehumidifier condensation coil and have it empty into a floor drain. If a floor drain is not available, you can elevate the unit and have it empty into a sink or tub.

Dehumidifier water collection tank with hose attached to side

Most new dehumidifiers have hose attachments directly on the coils. If the hose attachment is on the side of the water collection tank like the one shown here, there will always be stagnant water in the tank.

5) Do you have mold growth above your water tank?

It’s common to discover black mold hiding on the underside of dehumidifiers directly above the water collection tank. I also find mold growing on the tops and sides of tanks.

Mold growing inside dehumidifier above water collection tank      Mold growing on top of dehumidifier water collection tank

The solution here is the same as above in that you should bypass the tank altogether.

If a dehumidifier has already been put into service using the water collection tank, it should be inspected for mold and sanitized. Effective mold cleaning solutions should be used, and as always, safe mold remediation techniques should be followed to prevent personal exposure or spread of mold spores.

DIY Mold Inspection

If you see visible mold and mildew, detect a musty smell, or have any mold symptoms that could be related to your home, read the Do-It-Yourself Mold Inspection series from

Book cover for DIY Mold Inspection book

In this series you will learn how to perform your own mold inspection without the cost of hiring a mold remediation company, spending money on mold testing, or risking a common mold scam.

I’ll walk you through every room in your home, including the attic, garage, and basement/crawlspace. Using inspection photos with explanations, I’ll show you why and where to inspect for mold, and how to see hidden mold when it’s the same or similar colors as the surfaces it grows on.

Once you learn the methods of proper mold inspection, you’ll likely be surprised to see how much mold is actively affecting your indoor air quality and putting you at risk of mold symptoms. Typically, whenever mold is discovered in one location, you’ll find black mold, white mold, and other colors of mold growing in additional locations.

Don’t waste your money on mold testing

I often get calls from clients wanting me to do black mold testing, In good conscience, I try to talk people out of paying me to do this work.

Microscope for mold testing

Mold testing is largely a waste of money. Knowing the species of molds you have in your home is basically useless information. Your goal should be to find ALL areas of mold growth and safely eliminate them from your indoor environment.

Similarly, while air filters and air purifiers can significantly improve indoor air quality in mold-contaminated homes, they are NOT a substitute for a mold inspection.

You could easily spend hundreds (or thousands) of dollars purchasing products, testing for mold, or hiring professionals to look at your home, and still risk becoming a victim of incorrect information or buying devices that will not solve your problems. Wouldn’t you rather have expert information from easy-to-read books that are only $7.99?

Mold Remediation

Whenever mold is discovered, before proceeding with DIY mold remediation or hiring a professional mold removal company, the responsible thing to do is to become familiar with proper and improper methods of mold cleaning. You can do this by reading the book Do-It-Yourself Mold Cleaning and Prevention.

Book cover for DIY Mold Cleaning and Prevention

In this book I will teach you how to:

  • make your own mold remover solutions
  • protect yourself from mold exposure while performing mold removal
  • prevent mold spores from spreading further around your home
  • avoid being scammed by mold companies should you wish to hire one
  • prevent mold from returning

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4 Comments on “Dehumidifier Mold Exposure

  1. Can the black mold be inside the dehumidifier also? We’ve cleaned the filter, cleaned the tank and above the tank, where is was moldy. Now I’m afraid to turn it back in that we’ll have that smell in the house again!

    • Hi Kelly, it’s possible to have a few mold spores inside of dehumidifiers but they likely won’t be growing like they do in the areas shown in the photoes at the website. I wouldn’t be afraid to use your dehumidifier so long as you’ve cleaned the affected areas.

  2. This does not work right! I bought three books. Got a download page for the Mold that is a purple cover , book one and book two. I hit download on book one, tried to save it to my drop box and it wouldn’t let me, hit back to get to the other two books and can not find it! No instructions as to how to download or anything.

    • Hello and thanks for reaching out. Sorry to hear about your problems.

      The books are standard PDFs and they will download on to whichever device you were using at the time. I would suggest looking into your Downloads folder to find them, or perhaps your Documents folder if you have it set to receive downloads. Also, ensure you have sufficient room on the device to download them.

      You are also allowed to download them twice without paying for additional copies. You may want to download them onto a different device.

      Please keep me informed. One way or the other we’ll make sure things work for you.

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