ALERTA CO2: An alert system to monitor and mitigate the hazard associated with high concentrations of indoor and outdoor air CO2 at the inhabited areas of Puerto Naos and La Bombilla, La Palma

Anomalous CO₂ degassing were observed by the end of November 2021 in the neighborhoods of La Bombilla and Puerto Naos, and some banana plantations, located at the North-West flank of Cumbre Vieja volcano ridge, La Palma island, at about 6 km distance southwestern of the 2021 Tajogaite eruption vents. These urban areas, not directly damaged by lava flows, were included in the exclusion zone due to the strong volcanic-hydrothermal carbon dioxide emissions (CO₂>5-20%). CO₂ is an invisible toxic gas, as well as asphyxiant gas, and may be lethal when is present in concentrations higher than 14V%.

During the last two years, several institutions deployed indoor and outdoor own gas networks, to try to delimitate the CO₂ anomalies where CO₂ air concentration exceed hazardous thresholds, but with an insufficient number of CO₂ sensors (less than 100) to cover all homes, garages, basements and stores in real time. These studies aim to understand the dynamics of CO₂ emission to delimitate the CO₂ anomalies where CO₂ air concentration exceed the hazardous thresholds, and help the authorities’ decision-making of people's return to their homes and stores.

The ALERTACO2 project was born with the objective of implementing a much more extensive network of CO₂ sensors (1,200) sensors in most of the building of both inhabited areas, the creation of a 24-hour monitoring room and an information and awareness campaign for the population about this volcanic hazard. The financing (3M EUROS) comes from the Spanish Government, and has the participation of the National Geographic Institute (IGN) and the Volcanological Institute of the Canary Islands (INVOLCAN).

Each sensor has a color light code to indicate the CO₂ concentration (green, yellow, orange and blue if the sensor is not working), and a QR code to view the information remotely. So far 35% of the 1,200 sensors have been installed inside and outside homes of both urban areas (including beaches and Sol Melia Hotel). Each sensor sends the data to the 24-hour monitoring room via a gateway installed at the roof of each building. Thanks to the project, some families in the area marked green have been able to return to their homes in safety conditions in December 2023 since their homes CO₂ concentrations were below 1,000 ppm.