Mold itself is often mistakenly identified as a Volatile Organic Compound, or VOC. Mold is a fungus, a living organism that grows in damp environments, not a chemical compound that evaporates. The confusion arises because mold produces a specific subset of chemicals that fit the definition of a VOC, which are responsible for the distinct, musty odor associated with mold growth. The gases and particles mold releases have different implications for indoor air quality and human health.
Defining Volatile Organic Compounds
Volatile Organic Compounds are a diverse group of carbon-based chemicals that have a high vapor pressure at room temperature. This physical property, known as volatility, means they easily evaporate and enter the surrounding air as gases. A VOC is defined as a compound that readily off-gasses from a solid or liquid into the atmosphere.
VOCs originate from both natural and synthetic sources. Common household sources include paints, varnishes, cleaning supplies, adhesives, furniture, and personal care products. These compounds are responsible for the smells we associate with new cars, fresh paint, or certain cleaners. Concentrations of VOCs are often higher indoors than outdoors because of the number of products used within a confined space.
Microbial VOCs: The Mold Connection
Mold is not a VOC, but it actively produces compounds that fall under the VOC classification. These chemicals are specifically called Microbial Volatile Organic Compounds, or MVOCs, and they are byproducts of the mold’s metabolic processes. MVOCs are emitted as gases when mold consumes and breaks down organic materials like wood, drywall, and paper.
The musty, earthy, or “dirty sock” smell that alerts people to a mold problem is the direct result of MVOCs off-gassing. One well-known MVOC is 1-octen-3-ol, often called “mushroom alcohol,” which contributes to the characteristic fungal odor. This gaseous emission is distinct from mold spores, which are the microscopic reproductive units of the fungus that travel through the air to colonize new areas.
MVOC production is influenced by the type of mold, the material it is growing on, and the amount of moisture present. They serve various biological roles for the mold, including communication and defense mechanisms. The presence of MVOCs in the air indicates that mold is actively growing somewhere in the building, even if the growth is hidden behind walls or under flooring.
Health Effects of MVOC Exposure
Exposure to MVOCs can lead to a range of non-specific health symptoms due to their irritant properties. These compounds are systematic irritants that can affect multiple parts of the body upon inhalation. Common complaints include irritation of the eyes, nose, and throat, as MVOCs interact with mucous membranes.
Beyond localized irritation, MVOC exposure is frequently associated with systemic symptoms like headaches, dizziness, and fatigue. While the long-term toxicological effects of MVOCs are still being studied, research suggests a link between exposure and the exacerbation of asthma symptoms in sensitive individuals. The health risk in a mold-contaminated environment is often a combination of MVOCs, spores, and mycotoxins, which are non-volatile toxins produced by certain molds.
Identifying and Eliminating the Source
The most common method for identifying an MVOC problem is the presence of a persistent, musty odor. Specialized air quality testing, using devices like Sorbent tubes or Summa canisters, can confirm the presence of MVOCs and help pinpoint the general area of microbial growth. Because MVOCs are light vapors, they can be detected even if the mold is hidden behind barriers like drywall.
Since MVOCs are an ongoing byproduct of active mold metabolism, eliminating the odor requires stopping the mold growth itself. Simply masking the smell or cleaning visible surface mold is not an effective solution because MVOC production continues until the underlying issue is resolved.
The most effective action is source control: identifying and correcting the moisture source that allows the mold to flourish. This requires fixing leaks, managing humidity levels, and ensuring proper ventilation to keep organic materials dry. If mold growth is extensive, professional remediation is necessary to safely remove contaminated materials and prevent the mold from returning. Once the mold is removed and the moisture problem is fixed, the source of the MVOCs is eliminated, and the musty odor will eventually fade.