Older Western NC homes have plenty of charm. The musty smell is not part of it. We get calls every week from homeowners who have tried air purifiers, scented candles, and ozone machines — none of which fix the underlying issue, because the smell is being generated four feet below their feet.
The stack effect, in plain English
Warm air rises. As air leaves the upper floors of a home, it pulls replacement air up from the lowest point — usually the crawl space. Studies put the share of indoor air that originated in the crawl at 40–60%. If the crawl is humid, moldy, or has standing water, that is what is being breathed upstairs.
What the smell actually is
Microbial volatile organic compounds (mVOCs) released by mold and bacteria as they consume damp wood. They are distinctive: earthy, slightly sweet, with a sharp dirt-after-rain edge.
Fixing it for good
The only durable fix is to remove the source: dry the crawl space (drainage and dehumidifier), remediate any active mold growth, and seal the air pathway between crawl and living space (encapsulation, sealed access, sealed rim joist). Air purifiers upstairs do not address the inflow.