Which of the following is a sign of potential mold in a building?

A sign of potential mold in a building is indicated by an unpleasant musty odor. This characteristic smell often arises from the growth of mold and mildew, which thrive in humid and damp environments. When mold spores are present, they produce volatile organic compounds (VOCs) that create this distinct odor, alerting occupants to the possibility of mold presence, often before it becomes visually apparent.

In contrast, bright lighting systems, newly painted surfaces, and modern HVAC systems do not suggest any inherent risk or presence of mold. While these features can influence the overall environment of a building, they do not directly indicate mold issues. For instance, a modern HVAC system might help control humidity levels if properly maintained, reducing the likelihood of mold growth, and freshly painted surfaces could be clean and free of mold itself. Hence, the musty odor is a key indicator that should prompt a closer investigation into mold presence in the building.