Buildings Indoor Air Quality requires a control in the Relative Humidityparameter. In passive architecture in humid climates relative humidityis even more important for human comfort and difficult to control.Therefore, nowadays, there is a research on dehumidifying systems.The present article shows an innovative dehumidifying panel composedof a plaster and Calcium Chloride salt. Laboratory tests are carried outto establish its viability as an indoor air moister regulator integrated incommon plaster building interior coatings. There are two types of teststhat have been carried out in two consecutive empirical phases: in thefirst phase, the tests of characterization of the Calcium Chloride as adesiccant are carried out; in a second phase, the dehumidifying panelas a whole is tested. Finally, both types of empirical tests show theefficiency and viability as an air moisture passive control system.