Why a clean room-air test does not rule out mold
Air sampling measures what is circulating in the room you are standing in. That is genuinely useful information, and it is the right first test. But mold does not have to circulate to be a serious problem. When contamination is sealed inside wall cavities, behind drywall, or in an attic above an insulated ceiling, the spores largely stay where they are. The barrier that keeps them out of your air is the same barrier that keeps them out of the sample. That was exactly the situation in the Loch Lloyd project in Belton. Years of roof water intrusion had fed growth inside the wall assemblies and attic. The living space read clean because the contamination was contained by the very construction hiding it. A clean room-air test tells you the air is currently clean. It does not tell you the structure is.When to suspect something the air test missed
Cavity sampling is not necessary in every house. It is worth considering when:- There is a musty smell that testing does not explain. Your nose is detecting microbial volatile organic compounds, which move more freely than spores do.
- There is a known history of water intrusion — a roof leak, an ice dam, a plumbing failure, a chronically damp basement. Stachybotrys grows on cellulose-rich material like drywall paper and framing that has stayed wet for a long time. Its presence indicates chronic moisture, not a recent spill. Related: how quickly mold grows after water damage.
- Symptoms track with the building. People feel better away from the property and worse inside it.
- There is visible staining on the exterior side of a wall, at a roofline, or around a window.
