Mold Odor Control - How to Track Down Musty Odors

Finding mold, and household mold growth abatement

by Thad Godish, Ph.D

Editor's Note: You can link to FAQs and articles by Thad Godish and others in our Mold Center.

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Q. I smell a musty/moldy smell in my living room. I can narrow down the area of the smell, but can't seem to find the source. Any suggestions? - Debbie, Kentucky.

A. If you can smell it but can't see it, it must be inside one of the living room walls or under the living room if you have a crawlspace. If the living room is on the south or southwest side of your house and you have brick or stone veneer, it is likely that rain water has gotten into your wall particularly from wind-driven rains. If such is the case, the moldy/musty odor will be the strongest on breezy days.

Locating mold in a wall is difficult. Most professionals drill holes in such walls and collect mold samples to determine whether mold is present, the dominant mold types, and its relative concentrations.

Typically I use a non-destructive approach. I look for electrical outlets on the external wall. I take the plastic plate off and then use my odor detector (my nose). I often detect the presence of mold odors in external walls using this technique. It works best on a slightly breezy day when the wall is under positive pressure. It also words best if the infestation is near to the electrical box. If it is distant, you may not be able to detect it.

Mold infestation of exterior wall cavities is also common under windows, particularly windows subject to condensation and those that have been poorly caulked. Caulking is intended to prevent water from entering wall cavities. If it was poorly applied or maintained, water easily enters the wall around the window where infestation takes place.

For more information, go to the Indoor Environmental Notebook.

First Published: October 2002
Updated: April 2007

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