Monitoring of relative humidity in extreme environments: the hypogeum of “Tomba della Scimmia”

Hypogea are characterized by stable temperature (T) and high levels of relative humidity (RH). If measuring T is not complex through platinum resistance sensor (Pt 100 sensor), most thin film capacitive sensors for measuring RH can experience issues in damp environments. Indeed, in such conditions, water vapour can condense on the dielectric material, implying a significant error in the RH measurement. In this research, we study the performance of different kind of thermo-hygrometers within the hypogeum of Tomba della Scimmia (Chiusi, Italy). In this site, indoor climate monitoring has started in 2011 representing a unicum for the length of T and RH data series. It was found that the hygrometer commonly used for indoor monitoring is unable to detect any fasten RH drop if exposed to very damp environments. Even if hygrometers specifically developed to avoid condensation were used, they might provide the same erroneous RH values anyway.