Why Does My Humidifier Filter Turn Brown?

Humidifier filters are designed to keep the mist released into your environment clean. They work by removing dirt particles and any other impurities from the mist before the mist is released into the air in your home.

Short Answer: Why Does My Humidifier Filter Turn Brown?

Your humidifier filter could be turning brown because of the accumulation of dirt, dust particles, dust mites, mold, and or mineral deposits on the filter. Prolonged use of a filter without proper care can lead to the accumulation of dirt and mold.

Humidifier filters play an important role in humidifiers and need constant care and maintenance to ensure that the misty air released from the humidifier does not have impurities.

Continue reading to learn more about the role of humidifier filters, why your humidifier filter might be turning brown, and how to clean the filter and replace the filter.

In this post we will cover:

Role of a Humidifier Filter

Removing Impurities from the Water

The main role of humidifier filters is to remove impurities in the water. Before the water is released into your indoor air, it passes across the filter and most of the impurities such as dirt, dust mites, dust particles, minerals, and mold spores that might be present in the water are removed by the filter.

If you are using distilled water or purified water, you might not notice any dirt on your filter because of the processing used to remove such impurities during the distillation or water purification process.

On the other hand, if you are using tap water, hard water, rainwater, or any other type of water that has not been taken through extensive purification processes, then you might notice a build-up of these impurities on the filter.

Adding Moisture to the Air

Filters also control the level of moisture being released into the surrounding environment, because they control the amount of water being released at a time.

For instance, evaporative cool mist humidifiers rely on a complex filtration process that entails drawing air from its surrounding using a fan and blowing the air across a moist filter to moisturize it and remove any impurities present in the air.

This ensures that the mist released from the humidifier does not have any impurities. It also promotes the removal of impurities from the surrounding air.

As such, humidifier filters play two main roles that are critical in the performance of your humidifier. Maintaining the condition of the filter in your humidifier is important.

What is The Brown Stuff on My Humidifier Filter?

There are many reasons why your humidifier filter might be turning brown. The list below summarizes the most common reasons.

Mold Growth

Mold growth in your humidifier can turn the inner parts of your humidifier and the humidifier filter brown, especially if you do not follow the recommended maintenance guidelines for your humidifier.

Mold is likely to grow in any place with stagnant water. As such, if you do not clean your humidifier regularly, you are likely to notice a change in the color of its water tank and filter that might have been caused by mold spores.

Dirt, Dust Particles, and Dust Mites

Dirt, dust particles, and dust mites that might be present in the water you are using can also accumulate in your humidifier water tank and its filter.

If the air in your home is dusty, the dry air drawn in an evaporative humidifier might also contain dust particles and dust mites.

Mineral Deposits

Calcium and magnesium are the most common minerals linked to water hardness. If you are using hard water in your home and in your humidifier, these minerals can form a chalky-like residue inside your humidifier and on the humidifier filter.


If you are adding anything to your humidifier water, the substances might be responsible for discoloring your humidifier filter. Unless the humidifier has been designed with a diffuser, adding essential oils to the water might ruin your humidifier and its filter.

Humidifier Filter Maintenance

Empty the water in the humidifier when you are not using it

Keeping stagnant water in your humidifier when you are not using it can lead to mold growth and the accumulation of unpleasant microorganisms in the humidifier. The microbes can also accumulate in the filter and alter the color of the filter.

If you know that you will not be using your humidifier for a while, ensure that you empty the humidifier and clean it thoroughly before putting it in storage.

Keeping the filter clean

Keeping the filter clean is the first step toward ensuring that your humidifier will serve you well. If you notice some brown deposits on your filter clean it based on your manufacturer’s guidelines.

You can follow the simple instructions below on how to clean a humidifier filter if you do not have access to your manufacturer’s manual or you simply couldn’t be bothered to look for it.

You should clean the filter in your humidifier at least once every week. If you use your humidifier every day, you can opt to clean the filter more often depending on the type of water you use in your humidifier and how dirty the filter gets after using it for 48 to 72 hours.

To clean your humidifier you will need

  • White vinegar
  • Clean water
  • A soft sponge or a non-abrasive piece of clothing
  • Towel

How to Clean Humidifier Filter

Step 1: Disassemble the humidifier to remove the filter.

Step 2: Clean the humidifier’s water tank separately.

Step 3: Rinse the filter with running clean cold or lukewarm water.

Step 4: If you notice that your filter is clean after rinsing it you can place it on a towel to try.

Step 5: If you notice any brown residues on the filter you should soak it in a white vinegar solution.

Step 6: Use 50/50 white vinegar and clean water to formulate the solution in a small tin.

Step 7: Let the filter stay in the water for about 30 minutes before removing it and rinsing it again.

Step 8: After rinsing the filter, place the filter on a towel to dry the reassemble the humidifier

Note: You can also use the white vinegar solution to occasionally disinfect your filter and water tank, and remove any mineral deposits that might have accumulated over time.

Warning: Do not clean your humidifier filter with detergent as some of the chemical residues from the detergent could remain in the filter and end up being released into the air in your home. Exposure to such chemicals can be harmful to you.

Replace the Humidifier Filter: How do I know if My Humidifier Filter Needs Changing?

Humidifier filters should be replaced regularly to give you the best performance of your device. Different manufacturers have varying opinions regarding how often you should change the filter in your humidifier.

Ideally, you should change the filter in your humidifier at least after every three months. Depending on your usage and how often you use your humidifier, this timeline might be okay or too long for you.

If you use your humidifier regularly, you should change your filter after every six weeks or two months.

Some of the indications that will help you know when to change your humidifier filter include:

  • A worn or torn humidifier filter
  • A clogged filter that does not get clean or unclogged when cleaned
  • A filter that is not working properly i.e. reduced mist production
  • A filter that you have been using for about 3 months

In Summary

A humidifier filter is a critical component of a humidifier. You should ensure that you adhere to your manufacturer’s guidelines regarding the care and maintenance of the filter in your humidifier.

Avoid using the wrong type of water in your humidifier as that might clog the filter and affect the performance of your humidifier.

You should also ensure that you replace the filter in your humidifier at least after every three months. Replacing the filter after it is worn out or clogged is also important in ensuring that the mist released from the humidifier is clean and safe.

Recommended Read: Why the Water in Your Humidifier Might Turn Black

FAQs For Why Humidifier Filters Turn Brown

Why does my humidifier filter get so dirty?

The role of the humidifier filter is to trap dirt and prevent dirt from being released into the air within your home.

So when your filter gets dirty, it is because it is doing its intended job. However, a very dirty humidifier filter will not be able to filter out dirt and dust particles. When you notice that your humidifier filter is dirty, clean it to promote its efficiency.

How do I know if my humidifier filter needs changing?

Most modern humidifiers have an alert that lets you know when you need to change your humidifier filter. If your humidifier does not have an alert you should change your filter at least once after every three months. If you use your humidifier regularly, it is advisable to change the filter after every five to six weeks.

Yellow crust on humidifier filter

If you notice yellow or orange crust on your humidifier, the problem could be mineral deposits accumulation on the filter.

The minerals are usually present in hard water and the use of this type of water in most humidifiers that have not been designed to handle hard water can lead to accumulation of the mineral deposits that end up looking like orange or yellow crusts.

You can clean the filter using white vinegar solution to remove the yellow crusts. Simply mix a 50/50 solution of water and white vinegar and use it to clean the water tank of your humidifier and the filter.

Alternatively, you can use a CLR remover, which is a product that removes calcium, lime, and rust from surfaces. Check your manufacturer’s guidelines first to learn about how to clean your humidifier filter or use white vinegar before sourcing out for the CLR remover.

Mold on humidifier filter

Mold can accumulate on your humidifier filter especially if you leave water in your humidifier for a long time without cleaning the humidifier and replacing the water.

Stagnant water or damp conditions promote the growth of mold. So if you leave water in your humidifier for a long time, the water will create a breeding site for mold and other microorganisms.

Think of the humidifier filter as bread. If you leave bread on your kitchen counter for a long time, eventually mold will grow on the bread.

Humidifier filter gets hard

If your humidifier filter gets hard it is because of the presence of mineral deposits from the water you are using.

Most humidifiers are not designed for hard water and as such using hard water in those humidifiers promotes the accumulation of mineral deposits in the water tank, heating element, and/or filter.

Ensure that you use the right type of water for your humidifier. If you cannot access distilled water easily, consider investing in a humidifier designed for hard water.