The particular geological setting of the Azores archipelago is responsible for the occurrence of some potential destructive geological phenomena, as earthquakes and volcanic eruptions, which already caused several damages and the death of thousands of people since the settlement of the islands. Nowadays volcanic activity is characterized by the presence of fumaroles, thermal and CO2-rich cold springs, as well as soil diffuse degassing areas. Present work focus on the study of these permanent gas emissions, essentially hydrothermal fumaroles and carbon dioxide (CO2) degassing. Characterization and modelling of these manifestations is important for seismo-volcanic monitoring purposes since variations in the composition/flux of the gaseous emissions may work as precursory signals of volcanic unrest. Despite the importance of these studies for civil protection and emergency planning, some volcanic gases are also toxic and/or asphyxiant, and consequently need to be identified and studied in order to reduce public health problems. In the particular case of the CO2, that is an asphyxiant gas, indoor lethal concentrations were already measured and were responsible for the rehousing of some Azorean families. As CO2 is also one of the greenhouse gases, Azores islands are also a natural laboratory to quantify the CO2 naturally emitted and evaluate its importance for global warming. The understanding and modelling of the hydrothermal manifestations is also significant to detect not only areas with geothermal potential, but also to evaluate the impact that this kind of alternative energy can have in the environment.