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Lingering Musty Odors After Mold Remediation

Stinky, musty odor

A musty odor can be a telltale sign of a mold or moisture problem in a home. Perhaps in your own home, the odor was what prompted you to schedule a mold inspection! Once the mold is discovered and remediated, the odors will likely go away. But what happens when that musty smell lingers in the home after you’ve completed repairs?

A client reached out to us recently and explained that they had completed repairs to address a foundation crack (the source of her moisture problem), removed the affected moldy materials, washed clothes, and even went so far as having some trees on the property cut down so that the leaves wouldn’t clog gutters — but a musty smell remained. What is a homeowner or renter to do in a situation like this? When this client reached out to us, we advised them to start with three main things: control humidity, air out musty porous materials, and perform a detailed cleaning.

Step one: Control the humidity, control the musty odors

Operating a dehumidifier in the affected area is a good way to help keep relative humidity levels in the ideal range. Ideally, you should use a dehumidifier with a drain so that it can run continuously (rather than having to empty a bucket). If there is no nearby floor drain, some units have a pump that can lift the water into a nearby sink or tub. How do you know if you have properly controlled humidity? Use a device to measure and log relative humidity levels throughout the day. We would want to see the RH levels stay below 60% at all times, and lower is even better. 

Step two: Air out musty materials

Once humidity is under control, next you’ll want to get rid of the embedded musty odors.  Just like cigarette smoking can lead to odors getting embedded in porous materials and still be detectable after the smoker is gone, the same can happen with mold even after the moisture issue has been fixed.  Here, fresh air is your friend. Have the windows open in the affected space as much as possible. If you have musty contents (pictures, papers, etc.), spread them out outside on a warm day to help them air out. Carpeting can trap these musty odors as well, and it would be recommended to have it removed in affected areas where you’re noticing an odor.  If the outdoor air is very humid, then opening windows can create other moisture problems so ventilating the space needs some thought and planning.

Step three: Cleaning

Next, you should do a detailed clean of everything.  Mold can grow on dust, so keeping the home as spotless as possible reduces the number of available nutrients for mold to eat. Removing dust also eliminates another potential source of musty odors. Anything porous should be aggressively aired out outside, and larger items like a couch could be beaten with a tennis racquet. Reference this previous blog post to learn more about what should be kept or what should be discarded after a mold issue.

Final thoughts

While the suggestions above are a good starting point, there are other things to consider. Perhaps the remediation you performed didn’t remove everything.  If the area of concern is a finished basement, drywall and paneling can harbor musty odors and hide your view of cracks, seepage, and mold growth. This is a circumstance where a thorough moisture assessment with thermal imagery and a moisture meter could help to find any wet materials.

Other suggestions might be something like an ERV to continuously ventilate, a radon mitigation system to prevent soil gases from seeping in, or adding an outdoor air intake to your HVAC system. 

If you need professional help with suggestions for fixing a lingering odor or other IAQ concerns, give us a call at 312-920-9393!

Ian Cull

Ian Cull is a nationally recognized expert in the field of indoor air quality. He is the Chief Science Officer of Indoor Science, a company he started in 2004. He speaks around the world on air quality topics and is a training provider of the Indoor Air Quality Association. Mr. Cull is a Licensed Professional Engineer (PE) and Certified Industrial Hygienist (CIH). His degree is in Environmental Engineering from the University of Illinois - Urbana Champaign. Mr. Cull has developed 50 air quality related courses for the IAQA University and is the author of the book, “Fundamentals of Mold Remediation”. In his words… “Besides being passionate about indoor air quality, I enjoy cycling, music, the Chicago Bulls, and having fun with my three kids.”

2 thoughts on “Lingering Musty Odors After Mold Remediation

    Hey Marissa, thanks for your article.

    If you don’t eliminate the source of the odor, that mustiness will return. The root cause of musty smells is mold and mildew. As these fungi digest the materials they live on, they release noxious waste gases. The gases circulate through the air and are absorbed into soft items such as carpet, curtains, and furniture.


    Very true! Addressing the source is key to eliminating the problem and making sure it does not return. Thanks for your comment!