Is concrete gunning in volcanic tunnelling effective in reducing the presence of radon gas? Experience in road tunnels, the Canary Islands (Spain)

The Canary Islands are a radon-prone volcanic territory in Spain. The radon gas concentrations in the enclosed areas must be considered in terms of human health. Measurements of radon in the selected tunnel structures of Gran Canaria and Tenerife are taken to evaluate radon gas activity and possible harmful effects on workers if the advised radon concentrations are exceeded. Although there is a tendency toward high radon values on objects that are in contact with the ground, the obtained results show radon concentrations under the European regulatory limit concentrations (300 Bq/m (super 3) ). Average radon values measured with both passive and active detectors are less than 55 Bq/m (super 3) . Properties of the intermediate media that separates the ground from the tunnel, which in this case is concrete, seems to be a deciding factor for the observed low radon concentrations.