Fumaroles at the crater rim and diffuse degassing by soils are distinguished gas sources in the Island of Vulcano. The atmosphere receives volcanic gases, and the concentration of the air CO2 does change owing to the volcanic degassing. Although the flux and gas composition allowed tracking the fumarolic-solfataric degassing, the emissions of carbon dioxide and hydrogen sulfide caused gas hazards. The isotopic signature allows distinguishing among various CO2 (ie, volcanic, air, and exhaust gas derived from the burning of fossil fuel). Therefore, the stable isotopes in CO2 can help to identify the dominant gas sources at district scale based on mobile surveying, and tracking the volcanic gas hazard at Vulcano. Anomalous soil CO2 emissions were found near Faraglione settlements in addition to Palizzi, which is far enough the inhabited zone. Significant changes occurred in the CO2 degassing from these zones, because of the volcanic gas addition. This study shows the results of the survey aimed to identify four sites suitable for deployment of a monitoring system of the gas hazard at Faraglione. The survey was performed in summer 2020 and enabled collecting stable isotope composition measurements of the air CO2 and CO2 concentration indoor. The investigation targeted several types of environments including outdoor sites for a direct comparison with the indoor environment. Both the 13C/12C and 18O/16O of the air CO2 were determined by using a laser-based isotope mass spectrophotometer. A four-wheel car hosted the instrument, enabling isotopic measurements at 1 Hz, and meter-size spatial resolution. During the indoor survey, an infrared spectrophotometer enabled the air CO2 concentration measurements in the range of 0-10% vol. At least four measurements were performed at each site, with 2 minutes sampling frequency. The results allowed evaluating the CO2 concentration patterns in a time window (ie, 10 minutes) comparable with the Permissible Exposure Limit (PEL). The results show that indoor air CO2 concentration was above the current average air CO2 concentration (415 ppm vol) in several selected sites. Multiple sources of gases contributed to the CO2 level in the various sites as shown by the isotope signature of the air CO2. In a few specific sites, the air CO2 concentration achieved 6% vol after a few minutes of measurement, owing to the combination of high soil CO2 emissions and reduced air circulation. This value is higher than the Immediately Dangerous to Life and Health exposure limit (IDLH= 4% vol). The results of this study show that gas hazard mitigation includes several actions in the settled zones of Vulcano Porto. The soil CO2 flux and the air CO2 monitoring (ie, concentration and stable isotope composition) are compelling actions to decrease the volcanic risk.