Which environmental factor has the greatest influence on mold reproduction?

Mold reproduction is significantly influenced by the presence of free water in the environment. Mold spores require moisture to germinate and grow, as water is essential for many biological processes. When there is an abundant supply of free water, such as from leaks, high humidity, or flooding, mold can thrive, reproduce, and spread quickly.

While temperature fluctuations, air circulation, and light exposure can also affect mold growth, they do not have as direct or significant an impact on reproduction as the availability of moisture does. For instance, air circulation can help dry out an area, which would inhibit mold growth; similarly, certain temperature ranges may encourage or discourage mold growth. However, without sufficient free water, molds simply cannot reproduce effectively, regardless of other environmental conditions. Thus, the greatest influence on mold reproduction is indeed the availability of free water.