Which of the following is a common sign of indoor mold growth?

Unusual odors, particularly musty smells, are a common sign of indoor mold growth because mold releases volatile organic compounds (VOCs) as part of its metabolic processes. These VOCs are responsible for the characteristic musty smell associated with mold. When mold colonies grow and thrive in damp environments, they can emit these odors, which can often be detected before any visual signs of mold appear.

Recognizing these odors is crucial for early detection of mold issues, as they indicate the presence of moisture and organic material conducive to mold development. Addressing the moisture source promptly can prevent further mold growth and potential health risks associated with exposure.

The other options do not typically indicate the presence of mold. For instance, bright indoor lighting does not have a direct correlation with mold growth, nor do excessive noise from HVAC systems or cold drafts in certain rooms point to mold issues. These conditions might have various other causes, such as mechanical problems or temperature differences in the building, but they are not classic indicators of mold presence like musty odors are.