The person who asked this question probably wanted to know whether if one smells “earthy” or “musty” odours associated with mold, they would also be inhaling mold spores. The fact is we inhale some mold spores all the time. During summer, for example, we inhale more spores from outdoor air than from indoor air. However, in a building with mold growth problems airborne spores could be excessively high.

Smelling “musty” or “earthy” odours does not necessarily mean one is inhaling high levels of mold spores. While the smell could be due to microbial volatile organic compounds (usually abbreviated as MVOCs), some volatile organic compounds are not of microbial origin. Also, one of the MVOCs responsible for the “earthy” smell is geosmin. This compound is produced by not only molds but also by actinomycetes and other bacteria. Therefore, while the presence of VOCs may be an indication of hidden microbial contamination, they may not be a reliable indicator of microbial contamination or contamination by a specific microorganism.