Molds - Are They Detectable by Odor? Molds detection and growth Q&A

Editor's Note: You can link to FAQs and articles by Thad Godish and others in our Mold Center.

Q. What about sensory indicators of a mold problem? What is a person's threshold of detection? Does it vary with type of mold? Is a persistent rash/skin outbreak a symptom of exposure? I asked my doctor and she seemed to be clueless on IAQ/mold problems and effects. - John, New Jersey
A. For most individuals the only sensory indication that mold is present is the odor associated with compounds produced by mold when they are growing. These compounds are usually referred to as MVOCs or microbial volatile organic compounds.
MVOCs vary in their composition depending on the mold-type and the substrate (material) upon which they are growing. Some of the more commonly reported mold (there are also bacterial ones) MVOCs are 2-octene-3-ol, 1-octene-2-ol, 2-hexane, heptanone, and 3 -methyfuran. Most mold- produced MVOCs are alcohols or ketones. They are present in air in very low concentrations even in spaces that are heavily mold infested. Concentrations of individual MVOCs are likely to be in the few parts per billion (ppbv) range with combined concentrations in the 20-30 ppbv range.
As you can see, humans must have a very low odor threshold to detect these substances and, of course, we do. As with all odors this threshold varies considerably from individual to individual.
One of the scientific questions associated with MVOCs is whether exposure to them can cause health effects. Animal studies indicate that such exposures can cause sensory (mucous membrane) irritation but at much higher levels that are typical of mold-infested environments. On a personal level I experience strong sensory irritation of my nasal passages in heavily mold infested buildings even when I wear a respirator that filters out mold spores. That suggests that the sensory irritation is associated with exposure to gas-phase substances.
Exposure to mold with some exceptions is unlikely to cause skin rashes. The exceptions include handling mold-infested materials or sitting on mold-infested soft furniture or bedding. Mold can get into bedding such as box springs, mattresses, sheets and pillows. Such infestations are not uncommon in houses with very high humidity levels.