We’ve all gone into a basement and smelled that oppressive, musty, moldy odor. You know the odor…the one that makes you want to go back upstairs. If you have ever wondered what that odor is and what causes it, keep reading.
Most people identify these smells as “mold”. People sometimes refer to it as “mildew-odor” but mildew is, technically, fungal growth on plants.
When you notice this smell, you are not actually detecting mold spores since mold spores are odorless. What you ARE smelling is “microbial volatile organic compounds” or, MVOCs. MVOCs are vapors emitted from mold during certain environmental conditions and periods of their life cycle.
MVOCs may be irritating to people with an illness or odor-sensitive condition such as Multiple Chemical Sensitivity. But since if there is a mold odor there is mold it is hard to tell whether any irritation is due to the volatile chemicals or to immune system exposure to mold spores.
These volatile vapors can permeate deep into carpets, clothing, curtains, and upholstered furniture and can be difficult to impossible to remove. A thorough cleaning and exposure to fresh air often removes the worst of the odor. Launder in hot water or dry-clean clothing and curtains to get rid of odors. Keep in mind that you may have to discard carpets and upholstered furniture. Professional cleaning is your best shot to completely clean deeply embedded mold odor from carpeting and upholstery.
The MVOCs can change at various times throughout the year. Some mold varieties produce different odors depending on moisture conditions and food source, as well as producing odors only under specific ranges of temperature and humidity.
That being said, the only reliable way to control mold in a basement is to control the humidity—keep the basement relative humidity (RH) under 60%.
A good plan may be to first obtain a high quality, energy efficient dehumidifier. Then, remove as much basement contents as possible to expose them to fresh air and sunlight. This includes upholstered furnishings and carpet. Clean everything left behind with warm water and detergent using sponges and brushes. It is probably better to hire this job out to professionals.
When cleaning is done, start the dehumidifier in the basement and let it run on a very low humidity (~35%RH) setting for two days. If you still see damp areas, investigate them for water leaks and perform any necessary repairs. Within a few days the basement should begin to feel fresh and clean. Reset your dehumidifier to a more normal range (50-55%RH). Determine the fate of any old carpet (it will likely have to go) and any furniture or heavy fabric items.