CAN MOLD HIDDEN INSIDE YOUR WALLS AFFECT THE AIR YOU BREATHE? TWO NEW SCIENTIFIC STUDIES SHED LIGHT ON THE ANSWER.

Have you ever noticed a musty odor in your home that seems to come and go? Perhaps it’s stronger when the wind blows from a certain direction, when the bathroom exhaust fans are running, or when the kitchen range hood is turned on.

There’s a scientific explanation for why this can happen.

Two studies published in 2026 investigated how mold-related particles and gases can move from moisture-damaged wall structures into indoor environments.

MOLD PRODUCES MORE THAN JUST SPORES

As mold and other microorganisms grow, they can release gases known as microbial volatile organic compounds (MVOCs). Some of these compounds contribute to the familiar musty, earthy odors associated with damp buildings.

Unlike mold spores, which are particles, MVOCs are gases. They can move through small openings and air leakage pathways in building structures.

This helps explain why a home may have a persistent or intermittent musty odor even when no mold is visible.

WHY DOES THE ODOR COME AND GO?

Air pressure inside a home is constantly changing.

When bathroom exhaust fans, kitchen range hoods, or clothes dryers operate, they remove air from the home. If sufficient replacement air isn’t available, the house can develop negative pressure.

That negative pressure can draw air from wall cavities, crawl spaces, and other hidden areas through electrical outlets, plumbing penetrations, gaps around baseboards, and other openings.

Wind direction and speed can also change pressure relationships throughout a building.

If these hidden spaces contain microbial growth, the movement of air may carry mold-related particles and odor-producing gases into occupied rooms.

WHAT DOES THE NEW RESEARCH SHOW?

A 2026 study published in Building and Environment demonstrated that microbial particles can migrate from mold-contaminated wall structures. Researchers found that changes in air pressure, drying conditions, and air leakage pathways influenced this movement.

A second 2026 study, published in Science of the Total Environment, investigated chemical emissions from moisture-damaged wall structures.

Researchers identified four specific microbial volatile organic compounds associated with active mold growth. They also found that moisture levels within building materials were a major factor influencing these emissions.

Together, these studies reinforce an important point: Drywall does not necessarily prevent mold-related contaminants from reaching the indoor environment.

WHY TRADITIONAL AIR SAMPLING MAY MISS THE PROBLEM

A conventional room air sample measures airborne mold spores during a relatively short collection period.

It does not measure microbial gases, and it may not identify contamination hidden inside wall or ceiling cavities.

At Indoor Environmental Testing, we use our specialized Hidden Mold Detection System to investigate these spaces without removing drywall.

THE BOTTOM LINE

A musty odor that comes and goes should not automatically be dismissed simply because no mold is visible.

The source may be hidden inside a wall, ceiling, crawl space, or another part of the building.

And as these studies demonstrate, hidden mold is not necessarily isolated from the air inside your home.

Martine Davis, BBEC

Indoor Environmental Testing, Inc.
We detect what you suspect.

Scientific References:

1. Lappalainen, V., Sohlberg, E., & Pasanen, P. (2026). Simulation studies on the effect of microbial growth and moisture damaged materials on indoor air quality. Building and Environment, 301, 114799.
   https://doi.org/10.1016/j.buildenv.2026.114799
2. Lappalainen, V., Sorvari, J., Sohlberg, E., & Pasanen, P. (2026). Multivariate analysis on simulated moisture damage emission to indoor air. Science of the Total Environment, 1019, 181512.
   https://doi.org/10.1016/j.scitotenv.2026.181512