As mold inspectors, we hear this almost daily … “the mold is inside the wall so it can’t hurt you”. This phrase has been uttered by countless people, including builders, landlords, property managers, maintenance personnel, handymen, homeowners, even mold inspectors and mold remediators themselves!!
People wrongly assume that mold spores are what makes people sick. There are many more components of mold that can be harmful. Yes, in most cases, mold spores do not come out of a wall into the occupied space, however molds produce toxic gases called MVOCs (Microbial Volatile Organic Compounds).
These gases can easily travel out of wall cavities in the same way sewer gas or carbon monoxide can. They can circulate through electrical outlets, small cracks and under the baseboard. They CAN and DO affect occupants, sometimes in a major way.
For example, an office worker complained of severe headaches, flu- like symptoms, and brain fog when she was in the office. Symptoms went away during weekends when she was home. Her boss was skeptical that anything was wrong with the office but a cavity test of the wall behind her desk revealed Stachybotrys (aka Toxic Black Mold) was present. A roof leak has caused water to drip into the wall cavity and water was pooling behind the baseboard causing active growth.
These gases are also responsible for the musty smell that we associate with mold. If we don’t see mold, sometimes the musty odor is the only sign that mold is present in a room but sometimes there is no odor to warn us.
If the mold is no longer active (dormant) then it may not produce a gas but it could reactivate at any time when the temperature and humidity are just right.
Mold growth is often accompanied by bacterial growth and mycotoxins production. Bacteria produce toxic by-products called endotoxins. Some scientists believe these are even more poisonous than mycotoxins and mold-literate doctors are now asking patients to test their homes for both mycotoxins and endotoxins.
So mold inside walls should never be ignored unless the quantity is minute. It must be removed with proper controls by a professional mold remediation contractor who will use plastic containment, air scrubbers with negative air pressure and make sure mold will not be dispersed into the rest of the home. Once the mold is removed, the surfaces will then be disinfected and dried.
For more information about mold’s health effects visit the US EPA Mold Page
For information about Biological Pollutants in your home, see this article https://www.epa.gov/indoor-air-quality-iaq/biological-pollutants-impact-indoor-air-quality#Health_Effects