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.

Unfortunately the communities that most need these sensors cannot always afford them. A low-cost alternative developed by VolcanoTech, a company spun out from the University of Sheffield, is changing that.

VolcanoTech’s Pi-cam uses a smartphone camera modified to see in ultraviolet wavelengths, with a simple Raspberry Pi processor to interpret the results. This is able to read the fluorescence from sulphur dioxide; the more UV, the higher the level of gas. A network of such sensors costs a fraction of the price of comparable systems. VolcanoTech systems are already installed in Ecuador, Chile, Mexico, and Indonesia, with planned sites in Costa Rica and Argentina.

Large, low-cost sensor networks driven by commercial technology could transform air quality monitoring. Instead of having scattered data points, future meteorologists and vulcanologists might see a comprehensive picture, helping them to understand changes in air pollution as well as the risk of a volcanic eruption.