The objective for this study was to investigate and to perform a detailed survey of available sensors for quantification of relative humidity. The importance of relative humidity measurements becomes apparent in geotechnical applications, including in hydrogeologic characterization of contaminated sites, and creation of contaminant transport models. Survey of literature developed here includes all the recent advances in the development of relative humidity sensors using myriad of technologies including electrical optical, and chemical basis. Moreover, the survey includes basic research for development of the sensors as well as applications. Applications in all disciplines are considered for completeness. It turns out there is a need for fiber optic sensors as there has been very limited (one to two) sensors that have been developed using optical fiber sensor technology. These sensors have not been packaged for practical applications and therefore there is a need to start a project for packaging and fiber optic sensor for specific applications in geotechnical engineering.