VolcanoTech’s sulphur dioxide detecting sensors are in already in use in a number of countries Weather forecasts now include air quality warnings and cities have networks of air quality sensors driving real-time maps online. Similar air quality sensors can warn of an imminent volcanic eruption. Just as a fizzy drink releases carbon dioxide when the pressure is released, rising magma emits dissolved sulphur dioxide as it rises. So a big increase in this gas warns that a volcanic eruption may be imminent.