If your mold test came back negative but you still smell mold, the test may not have located the source of the problem. Air samples only capture spores moving through the air during a short testing window, and hidden mold behind walls, under floors, behind cabinets, or inside HVAC-related areas may not show up. A persistent musty smell should not be ignored, especially if there’s been past water damage. This article explains why mold tests can come back negative, what signs to watch for, and when a mold dog inspection may help find hidden mold.