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A study has been undertaken of radon levels in an abandoned metalliferous mine in South‐West England. Measurements have been taken in Gunnislake Old Adit using a variety of techniques. Radon gas levels of between 30,000Bq m^‐3 and 69,000Bq m^‐3 have been noted in this mine, associated with radon progeny levels of between 2.6 and 4.8 working levels. These radon levels pose a health risk for regular visitors to such mines.

In caves, radon has been identified as occurring at elevated levels by a number of groups but, with the exception of major show caves, its impact and risk to those who work in the caves has not received adequate attention thus far. This paper details surveys performed within a number of caves in a relatively “low risk” geographical area of the UK and proceeds to quantify the risk of exposure in those cave environments. Radon levels of 2,600 Bq m^–3 have been recorded but this is likely to underestimate the levels in many parts of the cave system for reasons associated with cave architecture, hydrology and aeration. A further survey was conducted within Goatchurch Cavern to investigate the effect of seasonal variations on the recorded radon concentration, from which an average summer to winter ratio of 4.79 was determined. Radiation doses to users of the caves were estimated and for occupational cavers doses of in excess of 16mSv were found to be likely.