Visible clues
Discoloration, spotting or fuzzy growth can be obvious signs, but appearance alone does not identify the mold species.
Moisture clues
Leaks, condensation, wet drywall, damp carpet, water stains and recurring humidity problems are worth investigating because moisture is the key condition that supports mold growth.
Hidden clues
A persistent musty odor or repeated staining after a leak may justify looking for concealed moisture or mold behind finishes.