Active Mold

Mold VOCs


Molds are fungi that grow in the form of multicellular filaments called hyphae that spread to form a network or colony called mycelium. There are thousands of known species of molds, although a much smaller number of mold species are commonly found in indoor environments.

Water intrusion and moisture are key elements that cause mold growth.  Often these conditions originate from leaky pipes behind walls or under floors, roof leaks, improperly installed windows or excessive humidity.  In many cases, these conditions are non-observable - we just don't know they exist.


Whether mold is visible or not, i.e., “hidden mold,” certain chemicals called mold volatile organic compounds (MVOCs) are produced as the mold digests its food.  Prolonged exposure to these VOCs can have serious health effects especially in infants, small children, the elderly and anyone with chemical sensitivities or chronic respiratory conditions like asthma or allergies.  Because mold VOCs are produced as the mold grows, they can be used as an indicator of active mold.  


There are a number of analysis options available that include mold VOCs, see the table below for a listing.



There are many possible places for mold to grow, some are less obvious than others.  The list below provides a few places to look.

  • Air conditioning units or drain lines

  • Near plumbing leaks

  • Near roof or wall leaks

  • Basement water intrusion from surrounding soil

  • Any consistently humid area

  • Near condensation around windows or any other condensation locations like exterior walls (typically where there is a temperature gradient that allows water to condense)

  • Freezer/refrigerator door seals, especially in summer

  • Freezer/refrigerator drain line and drip pan (if present)

  • Indoor plants

  • Empty beverage containers and glasses, especially if left for trash or recycling without being rinsed out

  • Wastebaskets and trash cans containing discarded food or wet items

  • Sump pumps, especially when the pump does not cycle often

  • Stand pipes and traps

  • Books, magazines, and newspapers if they have gotten wet or sit for a long time

  • Outside mold, especially if the air intake is near the ground and landscaping near the building uses wood chips or mulch

Mold VOCs

Mold VOCs (MVOCs) are produced during the metabolic or digestive processes of molds and therefore can be used as an indicator of actively growing mold. When mold is in an inactive or dormant state it does not produce many MVOCs and so cannot be used as an indicator of inactive mold. There are a number of factors that can affect the production and movement of MVOCs, including but not limited to the genus/ species, ventilation rates, temperature, humidity, growth surfaces, and competition from other molds. These factors make determination of the genus/species of mold very difficult so the presence of MVOCs indicates active mold growth but not the genus/species of the mold.


The most commonly recognized aspect of molds is the spores they produce as their primary means of reproduction. Spores are released from the mature mold body and spread by air currents and on people, animals, or materials that travel from place to place. These spores can remain viable for a long time until they find a suitable environment and grow to form new colonies.

Mycotoxins are chemicals that are produced during certain parts of the mold life cycle as secondary metabolites and can evoke a toxic response (e.g., severe allergic reactions and respiratory irritation and exacerbation of asthma symptoms or other respiratory ailments) in humans and animals. Mycotoxins have low volatility, meaning they have relatively low concentrations in air, so contact or ingestion rather than inhalation is often the main route of exposure for these chemicals.



Molds produce hundreds of VOCs but most have many other sources so they cannot be used as reliable indicators of active mold growth.  The 21 mold VOCs selected as indicators have few secondary sources and are fairly common across many mold genus/species.

IAQ Home Survey Inspect or Predict

TVOC, TMVOC, Home Contamination Index, Significant VOCs, Air Toxics

IAQ Home Survey Reveal

TVOC,TMVOC, Home Contamination Index, full chemical listing, Air Toxics

IAQ Commercial Survey Inspect or Predict

TVOC, TMVOC, CommercialContamination Index, Significant VOCs, Air Toxics

IAQ Commercial Survey Reveal

TVOC,TMVOC, Commercial Contamination Index, full chemical listing, Air Toxics

IAQ Basic and IAQ Check

TVOC, TMVOC, Significant VOCs


TVOC, individual MVOCs, TMVOC


TVOC, TMVOC, Top 5 VOCs, TO17 compounds, Semiquantitative compounds, Odorants, Air Toxics