What role does relative humidity (RH) play in mold growth?

Relative humidity (RH) is a critical factor in mold growth because it determines the amount of moisture available in the air. Mold spores need not only the right temperature but also a certain level of moisture to germinate and thrive. When relative humidity levels are at or above 60%, the air contains sufficient moisture that can condense on surfaces, creating the wet conditions conducive to mold development. Maintaining lower relative humidity levels is essential in preventing mold growth, as it limits moisture availability, which is a key element that mold requires to reproduce and spread.

While other factors mentioned can influence mold growth indirectly, such as air pressure, ventilation, and temperature, none are as fundamental as the role of relative humidity in providing the immediate moisture that mold needs.