Why Mold is on Styrofoam In an AC [SOLVED]

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Have you noticed mold on your Styrofoam in your ac and wondered how it got there? Styrofoam is not a common place for mold to grow simply because it doesn’t absorb water or moisture to make it a conducive environment for mold growth. But there are a few instances when mold can grow and appear on Styrofoam. However, it is still easy to get rid of it.

While it’s not common for mold to grow on Styrofoam, it can appear under certain conditions. So, to get rid of mold from Styrofoam, remove it and thoroughly clean it with some water mixed with 25% bleach and dish soap.

So, what causes mold on Styrofoam? The presence of water and some dirt can cause mold formation on Styrofoam as it loves to grow in wet environments.  So, let’s dive into details about how you can get rid of mold.

How To Get Rid of Mold on Styrofoam?

Styrofoam is usually used in window air conditioners to seal gaps between the ac unit and the window. The last part of your air conditioning system is where mold can develop. Fortunately, it’s so easy to clean it up, and here are a few steps to follow to remove mold:

Step 1. Unplug your window air conditioner to allow you to do the job safely.

Step 2. Remove the Styrofoam from installation. This is to help you see the extent of the mold and for you to clean it all around.

Step 3. Get white vinegar and a piece of cloth, then thoroughly clean the Styrofoam. (Undiluted white vinegar instantly kills mold).

Alternatively, you can use bleach. Mix bleach with some water and dampen a cloth into the mixture. Then thoroughly rub clean the Styrofoam with this mixture.

When you are done cleaning, put it back in position so that it can continue insulating your indoor air from the outdoor warmer air.

Mold can also grow on other parts of your air conditioning. One part that is likely to have mold growth is the coil. The indoor coil gets wet from condensate water, and mold loves to grow in wet environments.  

How to prevent mold in an air conditioner

Mold can grow on any part of the air conditioning system. But regular cleaning and proper maintenance (such as having a properly functioning drainage system of your ac system) can prevent mold growth, fungus formation, and unpleasant odors.

That said, if there is mold in your air conditioner, there are a few steps to get rid of it.

You’ll need to start with the following:

  • Open the cover of the air conditioner’s evaporator coil (indoor unit).
  • Carefully remove the filter and soak it in a bit of soap water.
  • Then use a no-rinse evaporator cleaner spray (you can order one online). The spray should typically remove both mold and odors in your air conditioner.
  • Now turn on the aircon in the “ventilation” mode. Then spray at the place of the air intake for a few seconds; The same spray can also be used to process the filter.
  • Finally, Leave the air conditioner in this mode for a few minutes, and that’s it.

Here is a great video on cleaning out mold in a window AC full of mold.


Should I remove the Styrofoam from my air conditioner?

No, Styrofoam seals the gaps between the air conditioner and the window. Removing the Styrofoam will make your air conditioner less efficient as the cool air will sneak outside, and warmer air will get in.

Can Styrofoam get moldy?

While this is not common, Styrofoam can get moldy when standing water and some dirt around it. Naturally, Styrofoam is a mold-resistant form of insulation. So excessive moisture coupled with an accumulation of material such as dirt can cause mold to grow on Styrofoam.

Does bleach harm Styrofoam?

Although some chemicals are known to dissolve Styrofoam, bleach doesn’t do any harm and does a great cleaning job compared to other chemicals. In short, you can safely use bleach on Styrofoam.

How do you know if your window air conditioner has mold?

Usually, when there is mold in your air conditioner, there will be foreign odors (it will stink.) Besides the smell, you can tell if there is mold in your air conditioner by looking at it. For example, you will see mold in the condenser, evaporator fins inside the drip pan, fan, and Styrofoam insulator bricks.

Final thought

We hope that this guide has been helpful to you.

Now that you have learned how to get rid of mold from Styrofoam in your ac effectively, we also hope you’ll be able to prevent mold from getting into your air conditioning system.

Thanks for reading.

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