Which of the following tools is essential during a mold inspection to analyze humidity?

A hygrometer is essential during a mold inspection to analyze humidity because it specifically measures the level of moisture in the air. Understanding humidity levels is crucial for identifying potential mold growth, as mold thrives in environments with high humidity. By using a hygrometer, inspectors can determine whether the indoor relative humidity is above the recommended levels, which is typically above 60%, creating a conducive environment for mold development.

While moisture meters are vital for measuring moisture content in building materials, and thermometers can provide information about temperature, neither tool is designed to measure humidity directly. A caliper is used for measuring the dimensions of objects and is not applicable to humidity measurement. Therefore, the hygrometer stands out as the appropriate instrument for assessing humidity levels in the context of mold inspections.