Clients often tell us that they smell mold and it's causing adverse health symptoms. However, they are confused when an air sample sent to the laboratory shows little to know spore activity in the areas of concern. Does this mean there is no mold and not to worry? No, what they are actually smelling is decay off-gassing from biological growth which includes molds, bacteria and biofilm. These odors contain microbial volatile organic compound (MVOC). People may compare this odor to a dank locker room, old cheese, dirty socks, or wet dog.
Microbial Volatile Organic Compound Overview:
The dank musty odor signifies the presence of microbial volatile organic compounds (MVOCs). Traditional volatile organic compounds (VOCs) are mainly industrial made chemicals with low molecular weights, high vapor pressure and low water solubility. MVOCs are released from metabolic processes of decay agents like fungi, bacteria and biofilm. The off gassing of MVOCs include a wide range of alcohols, ketones, aldehyde, esters, carboxylic acids, lactones, terpenes, aromatic hydrocarbons, sulfur and nitrogen compounds.
MVOCs produced during primary fungal metabolism include: Ethanol, 1-octen-3-ol, 2-octen-1-ol, and benzyl cyanide. MVOCs produced during secondary metabolism include 2-methyl-isoborneol, geosmin (1-10-dimethyl-trans-9-decalol) and terpenes.
Significance:
The perception of MVOC's is an indication that microbial growth is occurring. In the indoor environment, exposure to MVOC's has been blamed for headaches, nasal irritation, dizziness, fatigue, and nausea. Information on MVOCs produced in indoor settings and health effects is limited. The specific toxic properties and concentrations of MVOC's needed to produce symptoms are still unknown.
Recommendations:
Prudent and preventative measures should be taken to eliminate or reduce musty odors and associated MVOCs. These measures include but are not limited to:
- Professional HVAC system and air duct cleaning
- Disengage any built in humidification devices within the HVAC system
- Control humidity below 45% year round
- Replace carpeting with a more synthetic floor system
- Remove water damaged building materials
- Improve airflow in the home or building by encouraging fresh air with windows open or with an air recovery system (HRV/ERV)
