Many people have had experience of walking into damp dark structures in a hot humid summer day and felt smelly,musty, moldy scents in significant presence. Now we know those smells are small organic molecules disseminated by mostly molds actively growing. Those small organic molecules are called Microbial Volatile Organic Compounds (MVOCs), MVOCs are produced during active growth of microorganisms, especially molds.

MVOCs are low molecular weight chemicals in indoor environment due to active growth of bacteria and fungi. MVOCs apparently are impermeable through vinyl wallpaper, dry-walls or HVAC filters WITH or WITHOUT visible mold growth. In the latter case, mold growth may well be hidden growing somewhere.


Fourteen MVOCs have been categorized so far, they are: 3-methyl furan; 3-methyl-1-butanol; 3-methyl-2-butanol; 2-pentanol; 2-hexanone; 2-heptanone; 3-octanone; 3-octanol; 1-octen-3-ol; 2-octen-1-ol; 2-nonanone; Borneol; Geosmin.


According to a report from University of Ohio, the so-called black mold, Sick-Home-Syndrome agent, Stachybotrys chartarum produces a single MVOC (1-butanol) on gypsum board medium, whereas it produces many MVOCs: thujopsene, 1-butanol, 3-methyl-1-butanol, and 3-methyl-2-butanol on richer rice media.


Research shows that while mold MVOCs may contribute to health effects, particularly in residential housing, many symptoms are similar like allergenic responses, such as itchiness, rash, running-nose, fatigue, watery eyes, etc, though exposure to MVOCs has not been conclusively linked to health effects so far.


Yet, one thing is for sure, i.e. a smelly moldy house signifies the presence of MVOCs, therefore, active growth of molds or even bacteria.