Carbon dioxide (CO2) together with water vapor (H2O) and sulfur dioxide (SO2) are usually the most abundant gases released to the atmosphere during volcanic eruptions (Giggenbach, 1996; Fischer and Chiodini, 2015 and references therein). During non-eruptive periods, gas emissions are also frequent in many volcanic systems not only through the presence of permanent fumaroles, but also due to the existence of thermal and cold CO2-rich springs, as well as soil diffuse degassing emissions (Allard et al., 1991; Chiodini et al., 1998).