Survey Analysis Supplemental Information 

Volatile Organic Compounds (VOCs)

Mold VOCs

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Volatile organic compounds (VOCs) are everywhere. The "organic" part simply means these chemical compounds contain carbon, which makes them an integral part of everything around us. 

The presence of chemicals in your home can cause a wide range of problems, from an unpleasant odor to physical symptoms (burning and irritation in the eyes, nose, and throat; headaches; nausea; nervous system effects; severe illness; etc.). In some cases, these conditions may make the home unlivable. Anyone with respiratory issues like asthma or allergies, as well as children, the elderly, and pregnant women are more susceptible to poor indoor air quality than healthy individuals. However, at higher TVOC levels even healthy individuals are likely to experience ill effects.

VOC References

1 L. Molhave, Volatile Organic Compounds, Indoor Air Quality and Health, Vol. 5, International Indoor Air Quality Conference, Toronto, Canada, 1990, p. 22 ff.

2 European Collaborative Action: Indoor Air Quality and its Impact on Man (ECA-IAQ), Report No 19 Total Volatile Organic Compounds (TVOC) in Indoor Air Quality Investigations, 1997. (from L. Molhave et al., Total Volatile Organic Compound (TVOC) in Indoor Air Quality Investigation, Indoor Air 1997; 225-240.)

3 T. Salthammer, Critical evaluation of approaches in setting indoor air quality guidelines and reference values, Chemosphere 82, 2011, 1507-1517.



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.

Molds can affect humans and animals in their vicinity in several ways. The most commonly known 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. In addition to spores, mycotoxins can also be released under certain
situations. Mycotoxins are chemicals that are produced during certain parts of the mold life cycle 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.

Finally, 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: 

  • genus/ species

  • ventilation rates

  • temperature

  • humidity

  • growth surfaces

  • 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.

Mold can grow anywhere that satisfies four primary conditions.

  1. Presence of mold spores – spores are everywhere and it is very difficult if not impossible to remove them completely.

  2. Appropriate growth surface or nutrient source – molds are adaptable and can grow on almost any surface; many molds especially like cellulose-based materials (e.g., wood, drywall, insulation, cardboard, paper, carpet, etc.).

  3. Appropriate temperature – although many molds grow best in warmer temperatures, given enough time mold can  grow at almost any temperature condition.

  4. Water – this is the most significant and most important criteria since the other conditions are too commonly available to be controlled. The consensus of most organizations with a perspective on air quality (e.g., WHO, EPA, AIHA, ASHRAE, etc.) ͣ is that controlling moisture and dampness is the only way to consistently control or limit mold growth.

Mold Sources
Since there are so many possible locations that mold can grow, it can be difficult to locate without visual indicators. However,
there are some potential locations where molds are often found, as listed here.

  • 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 home uses wood chips or mulch


Typically, if there is no plumbing leak, condensation, or water intrusion, there will not be a mold problem. If active
mold growth is indicated, the first step in fixing the problem is to find and repair the water intrusion or moisture build up.
Some new or extensively renovated buildings can have high MVOC results. Additional dampness is often introduced into a new
building during the construction process (e.g., newly installed cement) and can lead to optimal mold growth conditions. Also, some
building materials may have mold growth on them when they are installed due to exposure to water before installation. It is
strongly recommended that new buildings or those with extensive renovation undergo a drying process to eliminate or reduce the
potential for mold growth.

The TMVOC value is an assessment of the quantity of actively growing mold. Like TVOC, no
government unit or organization has specified limits for TMVOC. The levels below describe the effects individuals exposed to
these TMVOC values may experience. These levels are qualitative estimates of possible effects experienced by healthy
individuals. Sensitive individuals or those with chronic or respiratory issues may experience effects at much lower levels. Mold
may be visible on a surface but in an inactive state resulting in little or no production of MVOCs. Regardless of the TMVOC result if
mold is visible it should be removed since molds may still produce spores or mycotoxins in an inactive state and new exposure to
water or moisture can initiate new mold growth. Since MVOCs are VOCs, they can be affected by the same environmental
conditions that affect other VOCs. Primarily lower temperature and higher air flow or ventilation will reduce MVOC concentrations.
Any water or moisture issues should be addressed quickly to limit the potential for mold growth.

These levels were determined empirically through interaction with air quality professionals regarding the reported health effects
experienced by individuals exposed to actively growing mold.

TMVOC (ng/L) Level Description


  • < 8 Minimal or Ambient Actively growing molds may be present, but are at or below levels found in most homes (i.e., these levels could be considered ambient or background).

  • 8 - 30 Active - Moderate Actively growing molds are present, but are at levels which typically only affect people sensitive to molds. Investigate possible water or moisture sources. 

  • 30 - 80 Active - Elevated Significant levels of actively growing molds are present; reactions or symptoms are probable.

  • 80-150 Active - High High levels of actively growing molds are present; high probability that all occupants will be affected; take immediate action to locate and remove mold.

  • > 150 Active - Severe Excessive levels of actively growing molds are present; all occupants will be affected; take immediate action to locate and remove mold. 


Useful Links

Additional Information about VOCs

Additional Information about Mold 


Additional Resources

  • CA CREL Chronic Reference Exposure Levels – CRELs, RELs

  • ATSDR Minimal Risk Levels – MRLs

  • EPA  Regional Screening Levels – RSL

  • EPA Reference Concentration – RfC

  • EPA Vapor intrusion guidelines