What factor significantly contributes to mold growth indoors?

High humidity levels are a significant factor that contributes to mold growth indoors because mold thrives in moist environments. When the humidity level rises, particularly above 60%, it creates an ideal breeding ground for mold spores. Mold requires moisture to penetrate surfaces and grow, which is why areas with high humidity—like bathrooms, kitchens, and basements—are often where mold problems are most evident.

Moreover, maintaining a lower humidity level, typically around 30% to 50%, can help reduce the likelihood of mold growth. This is why it's important to use dehumidifiers and ensure proper ventilation in areas prone to moisture to control humidity levels effectively. Other factors, such as inadequate air circulation and poor drainage, can also contribute to mold growth, but high humidity is one of the most critical conditions that create a favorable environment for mold proliferation.